1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Copyright (C) 1994 Linus Torvalds 4 * 5 * Cyrix stuff, June 1998 by: 6 * - Rafael R. Reilova (moved everything from head.S), 7 * <rreilova@ececs.uc.edu> 8 * - Channing Corn (tests & fixes), 9 * - Andrew D. Balsa (code cleanup). 10 */ 11 #include <linux/init.h> 12 #include <linux/utsname.h> 13 #include <linux/cpu.h> 14 #include <linux/module.h> 15 #include <linux/nospec.h> 16 #include <linux/prctl.h> 17 #include <linux/sched/smt.h> 18 #include <linux/pgtable.h> 19 #include <linux/bpf.h> 20 21 #include <asm/spec-ctrl.h> 22 #include <asm/cmdline.h> 23 #include <asm/bugs.h> 24 #include <asm/processor.h> 25 #include <asm/processor-flags.h> 26 #include <asm/fpu/api.h> 27 #include <asm/msr.h> 28 #include <asm/vmx.h> 29 #include <asm/paravirt.h> 30 #include <asm/alternative.h> 31 #include <asm/set_memory.h> 32 #include <asm/intel-family.h> 33 #include <asm/e820/api.h> 34 #include <asm/hypervisor.h> 35 #include <asm/tlbflush.h> 36 37 #include "cpu.h" 38 39 static void __init spectre_v1_select_mitigation(void); 40 static void __init spectre_v2_select_mitigation(void); 41 static void __init retbleed_select_mitigation(void); 42 static void __init spectre_v2_user_select_mitigation(void); 43 static void __init ssb_select_mitigation(void); 44 static void __init l1tf_select_mitigation(void); 45 static void __init mds_select_mitigation(void); 46 static void __init md_clear_update_mitigation(void); 47 static void __init md_clear_select_mitigation(void); 48 static void __init taa_select_mitigation(void); 49 static void __init mmio_select_mitigation(void); 50 static void __init srbds_select_mitigation(void); 51 static void __init l1d_flush_select_mitigation(void); 52 53 /* The base value of the SPEC_CTRL MSR without task-specific bits set */ 54 u64 x86_spec_ctrl_base; 55 EXPORT_SYMBOL_GPL(x86_spec_ctrl_base); 56 57 /* The current value of the SPEC_CTRL MSR with task-specific bits set */ 58 DEFINE_PER_CPU(u64, x86_spec_ctrl_current); 59 EXPORT_SYMBOL_GPL(x86_spec_ctrl_current); 60 61 static DEFINE_MUTEX(spec_ctrl_mutex); 62 63 /* 64 * Keep track of the SPEC_CTRL MSR value for the current task, which may differ 65 * from x86_spec_ctrl_base due to STIBP/SSB in __speculation_ctrl_update(). 66 */ 67 void write_spec_ctrl_current(u64 val, bool force) 68 { 69 if (this_cpu_read(x86_spec_ctrl_current) == val) 70 return; 71 72 this_cpu_write(x86_spec_ctrl_current, val); 73 74 /* 75 * When KERNEL_IBRS this MSR is written on return-to-user, unless 76 * forced the update can be delayed until that time. 77 */ 78 if (force || !cpu_feature_enabled(X86_FEATURE_KERNEL_IBRS)) 79 wrmsrl(MSR_IA32_SPEC_CTRL, val); 80 } 81 82 u64 spec_ctrl_current(void) 83 { 84 return this_cpu_read(x86_spec_ctrl_current); 85 } 86 EXPORT_SYMBOL_GPL(spec_ctrl_current); 87 88 /* 89 * AMD specific MSR info for Speculative Store Bypass control. 90 * x86_amd_ls_cfg_ssbd_mask is initialized in identify_boot_cpu(). 91 */ 92 u64 __ro_after_init x86_amd_ls_cfg_base; 93 u64 __ro_after_init x86_amd_ls_cfg_ssbd_mask; 94 95 /* Control conditional STIBP in switch_to() */ 96 DEFINE_STATIC_KEY_FALSE(switch_to_cond_stibp); 97 /* Control conditional IBPB in switch_mm() */ 98 DEFINE_STATIC_KEY_FALSE(switch_mm_cond_ibpb); 99 /* Control unconditional IBPB in switch_mm() */ 100 DEFINE_STATIC_KEY_FALSE(switch_mm_always_ibpb); 101 102 /* Control MDS CPU buffer clear before returning to user space */ 103 DEFINE_STATIC_KEY_FALSE(mds_user_clear); 104 EXPORT_SYMBOL_GPL(mds_user_clear); 105 /* Control MDS CPU buffer clear before idling (halt, mwait) */ 106 DEFINE_STATIC_KEY_FALSE(mds_idle_clear); 107 EXPORT_SYMBOL_GPL(mds_idle_clear); 108 109 /* 110 * Controls whether l1d flush based mitigations are enabled, 111 * based on hw features and admin setting via boot parameter 112 * defaults to false 113 */ 114 DEFINE_STATIC_KEY_FALSE(switch_mm_cond_l1d_flush); 115 116 /* Controls CPU Fill buffer clear before KVM guest MMIO accesses */ 117 DEFINE_STATIC_KEY_FALSE(mmio_stale_data_clear); 118 EXPORT_SYMBOL_GPL(mmio_stale_data_clear); 119 120 void __init check_bugs(void) 121 { 122 identify_boot_cpu(); 123 124 /* 125 * identify_boot_cpu() initialized SMT support information, let the 126 * core code know. 127 */ 128 cpu_smt_check_topology(); 129 130 if (!IS_ENABLED(CONFIG_SMP)) { 131 pr_info("CPU: "); 132 print_cpu_info(&boot_cpu_data); 133 } 134 135 /* 136 * Read the SPEC_CTRL MSR to account for reserved bits which may 137 * have unknown values. AMD64_LS_CFG MSR is cached in the early AMD 138 * init code as it is not enumerated and depends on the family. 139 */ 140 if (boot_cpu_has(X86_FEATURE_MSR_SPEC_CTRL)) 141 rdmsrl(MSR_IA32_SPEC_CTRL, x86_spec_ctrl_base); 142 143 /* Select the proper CPU mitigations before patching alternatives: */ 144 spectre_v1_select_mitigation(); 145 spectre_v2_select_mitigation(); 146 /* 147 * retbleed_select_mitigation() relies on the state set by 148 * spectre_v2_select_mitigation(); specifically it wants to know about 149 * spectre_v2=ibrs. 150 */ 151 retbleed_select_mitigation(); 152 /* 153 * spectre_v2_user_select_mitigation() relies on the state set by 154 * retbleed_select_mitigation(); specifically the STIBP selection is 155 * forced for UNRET. 156 */ 157 spectre_v2_user_select_mitigation(); 158 ssb_select_mitigation(); 159 l1tf_select_mitigation(); 160 md_clear_select_mitigation(); 161 srbds_select_mitigation(); 162 l1d_flush_select_mitigation(); 163 164 arch_smt_update(); 165 166 #ifdef CONFIG_X86_32 167 /* 168 * Check whether we are able to run this kernel safely on SMP. 169 * 170 * - i386 is no longer supported. 171 * - In order to run on anything without a TSC, we need to be 172 * compiled for a i486. 173 */ 174 if (boot_cpu_data.x86 < 4) 175 panic("Kernel requires i486+ for 'invlpg' and other features"); 176 177 init_utsname()->machine[1] = 178 '0' + (boot_cpu_data.x86 > 6 ? 6 : boot_cpu_data.x86); 179 alternative_instructions(); 180 181 fpu__init_check_bugs(); 182 #else /* CONFIG_X86_64 */ 183 alternative_instructions(); 184 185 /* 186 * Make sure the first 2MB area is not mapped by huge pages 187 * There are typically fixed size MTRRs in there and overlapping 188 * MTRRs into large pages causes slow downs. 189 * 190 * Right now we don't do that with gbpages because there seems 191 * very little benefit for that case. 192 */ 193 if (!direct_gbpages) 194 set_memory_4k((unsigned long)__va(0), 1); 195 #endif 196 } 197 198 /* 199 * NOTE: This function is *only* called for SVM. VMX spec_ctrl handling is 200 * done in vmenter.S. 201 */ 202 void 203 x86_virt_spec_ctrl(u64 guest_spec_ctrl, u64 guest_virt_spec_ctrl, bool setguest) 204 { 205 u64 msrval, guestval = guest_spec_ctrl, hostval = spec_ctrl_current(); 206 struct thread_info *ti = current_thread_info(); 207 208 if (static_cpu_has(X86_FEATURE_MSR_SPEC_CTRL)) { 209 if (hostval != guestval) { 210 msrval = setguest ? guestval : hostval; 211 wrmsrl(MSR_IA32_SPEC_CTRL, msrval); 212 } 213 } 214 215 /* 216 * If SSBD is not handled in MSR_SPEC_CTRL on AMD, update 217 * MSR_AMD64_L2_CFG or MSR_VIRT_SPEC_CTRL if supported. 218 */ 219 if (!static_cpu_has(X86_FEATURE_LS_CFG_SSBD) && 220 !static_cpu_has(X86_FEATURE_VIRT_SSBD)) 221 return; 222 223 /* 224 * If the host has SSBD mitigation enabled, force it in the host's 225 * virtual MSR value. If its not permanently enabled, evaluate 226 * current's TIF_SSBD thread flag. 227 */ 228 if (static_cpu_has(X86_FEATURE_SPEC_STORE_BYPASS_DISABLE)) 229 hostval = SPEC_CTRL_SSBD; 230 else 231 hostval = ssbd_tif_to_spec_ctrl(ti->flags); 232 233 /* Sanitize the guest value */ 234 guestval = guest_virt_spec_ctrl & SPEC_CTRL_SSBD; 235 236 if (hostval != guestval) { 237 unsigned long tif; 238 239 tif = setguest ? ssbd_spec_ctrl_to_tif(guestval) : 240 ssbd_spec_ctrl_to_tif(hostval); 241 242 speculation_ctrl_update(tif); 243 } 244 } 245 EXPORT_SYMBOL_GPL(x86_virt_spec_ctrl); 246 247 static void x86_amd_ssb_disable(void) 248 { 249 u64 msrval = x86_amd_ls_cfg_base | x86_amd_ls_cfg_ssbd_mask; 250 251 if (boot_cpu_has(X86_FEATURE_VIRT_SSBD)) 252 wrmsrl(MSR_AMD64_VIRT_SPEC_CTRL, SPEC_CTRL_SSBD); 253 else if (boot_cpu_has(X86_FEATURE_LS_CFG_SSBD)) 254 wrmsrl(MSR_AMD64_LS_CFG, msrval); 255 } 256 257 #undef pr_fmt 258 #define pr_fmt(fmt) "MDS: " fmt 259 260 /* Default mitigation for MDS-affected CPUs */ 261 static enum mds_mitigations mds_mitigation __ro_after_init = MDS_MITIGATION_FULL; 262 static bool mds_nosmt __ro_after_init = false; 263 264 static const char * const mds_strings[] = { 265 [MDS_MITIGATION_OFF] = "Vulnerable", 266 [MDS_MITIGATION_FULL] = "Mitigation: Clear CPU buffers", 267 [MDS_MITIGATION_VMWERV] = "Vulnerable: Clear CPU buffers attempted, no microcode", 268 }; 269 270 static void __init mds_select_mitigation(void) 271 { 272 if (!boot_cpu_has_bug(X86_BUG_MDS) || cpu_mitigations_off()) { 273 mds_mitigation = MDS_MITIGATION_OFF; 274 return; 275 } 276 277 if (mds_mitigation == MDS_MITIGATION_FULL) { 278 if (!boot_cpu_has(X86_FEATURE_MD_CLEAR)) 279 mds_mitigation = MDS_MITIGATION_VMWERV; 280 281 static_branch_enable(&mds_user_clear); 282 283 if (!boot_cpu_has(X86_BUG_MSBDS_ONLY) && 284 (mds_nosmt || cpu_mitigations_auto_nosmt())) 285 cpu_smt_disable(false); 286 } 287 } 288 289 static int __init mds_cmdline(char *str) 290 { 291 if (!boot_cpu_has_bug(X86_BUG_MDS)) 292 return 0; 293 294 if (!str) 295 return -EINVAL; 296 297 if (!strcmp(str, "off")) 298 mds_mitigation = MDS_MITIGATION_OFF; 299 else if (!strcmp(str, "full")) 300 mds_mitigation = MDS_MITIGATION_FULL; 301 else if (!strcmp(str, "full,nosmt")) { 302 mds_mitigation = MDS_MITIGATION_FULL; 303 mds_nosmt = true; 304 } 305 306 return 0; 307 } 308 early_param("mds", mds_cmdline); 309 310 #undef pr_fmt 311 #define pr_fmt(fmt) "TAA: " fmt 312 313 enum taa_mitigations { 314 TAA_MITIGATION_OFF, 315 TAA_MITIGATION_UCODE_NEEDED, 316 TAA_MITIGATION_VERW, 317 TAA_MITIGATION_TSX_DISABLED, 318 }; 319 320 /* Default mitigation for TAA-affected CPUs */ 321 static enum taa_mitigations taa_mitigation __ro_after_init = TAA_MITIGATION_VERW; 322 static bool taa_nosmt __ro_after_init; 323 324 static const char * const taa_strings[] = { 325 [TAA_MITIGATION_OFF] = "Vulnerable", 326 [TAA_MITIGATION_UCODE_NEEDED] = "Vulnerable: Clear CPU buffers attempted, no microcode", 327 [TAA_MITIGATION_VERW] = "Mitigation: Clear CPU buffers", 328 [TAA_MITIGATION_TSX_DISABLED] = "Mitigation: TSX disabled", 329 }; 330 331 static void __init taa_select_mitigation(void) 332 { 333 u64 ia32_cap; 334 335 if (!boot_cpu_has_bug(X86_BUG_TAA)) { 336 taa_mitigation = TAA_MITIGATION_OFF; 337 return; 338 } 339 340 /* TSX previously disabled by tsx=off */ 341 if (!boot_cpu_has(X86_FEATURE_RTM)) { 342 taa_mitigation = TAA_MITIGATION_TSX_DISABLED; 343 return; 344 } 345 346 if (cpu_mitigations_off()) { 347 taa_mitigation = TAA_MITIGATION_OFF; 348 return; 349 } 350 351 /* 352 * TAA mitigation via VERW is turned off if both 353 * tsx_async_abort=off and mds=off are specified. 354 */ 355 if (taa_mitigation == TAA_MITIGATION_OFF && 356 mds_mitigation == MDS_MITIGATION_OFF) 357 return; 358 359 if (boot_cpu_has(X86_FEATURE_MD_CLEAR)) 360 taa_mitigation = TAA_MITIGATION_VERW; 361 else 362 taa_mitigation = TAA_MITIGATION_UCODE_NEEDED; 363 364 /* 365 * VERW doesn't clear the CPU buffers when MD_CLEAR=1 and MDS_NO=1. 366 * A microcode update fixes this behavior to clear CPU buffers. It also 367 * adds support for MSR_IA32_TSX_CTRL which is enumerated by the 368 * ARCH_CAP_TSX_CTRL_MSR bit. 369 * 370 * On MDS_NO=1 CPUs if ARCH_CAP_TSX_CTRL_MSR is not set, microcode 371 * update is required. 372 */ 373 ia32_cap = x86_read_arch_cap_msr(); 374 if ( (ia32_cap & ARCH_CAP_MDS_NO) && 375 !(ia32_cap & ARCH_CAP_TSX_CTRL_MSR)) 376 taa_mitigation = TAA_MITIGATION_UCODE_NEEDED; 377 378 /* 379 * TSX is enabled, select alternate mitigation for TAA which is 380 * the same as MDS. Enable MDS static branch to clear CPU buffers. 381 * 382 * For guests that can't determine whether the correct microcode is 383 * present on host, enable the mitigation for UCODE_NEEDED as well. 384 */ 385 static_branch_enable(&mds_user_clear); 386 387 if (taa_nosmt || cpu_mitigations_auto_nosmt()) 388 cpu_smt_disable(false); 389 } 390 391 static int __init tsx_async_abort_parse_cmdline(char *str) 392 { 393 if (!boot_cpu_has_bug(X86_BUG_TAA)) 394 return 0; 395 396 if (!str) 397 return -EINVAL; 398 399 if (!strcmp(str, "off")) { 400 taa_mitigation = TAA_MITIGATION_OFF; 401 } else if (!strcmp(str, "full")) { 402 taa_mitigation = TAA_MITIGATION_VERW; 403 } else if (!strcmp(str, "full,nosmt")) { 404 taa_mitigation = TAA_MITIGATION_VERW; 405 taa_nosmt = true; 406 } 407 408 return 0; 409 } 410 early_param("tsx_async_abort", tsx_async_abort_parse_cmdline); 411 412 #undef pr_fmt 413 #define pr_fmt(fmt) "MMIO Stale Data: " fmt 414 415 enum mmio_mitigations { 416 MMIO_MITIGATION_OFF, 417 MMIO_MITIGATION_UCODE_NEEDED, 418 MMIO_MITIGATION_VERW, 419 }; 420 421 /* Default mitigation for Processor MMIO Stale Data vulnerabilities */ 422 static enum mmio_mitigations mmio_mitigation __ro_after_init = MMIO_MITIGATION_VERW; 423 static bool mmio_nosmt __ro_after_init = false; 424 425 static const char * const mmio_strings[] = { 426 [MMIO_MITIGATION_OFF] = "Vulnerable", 427 [MMIO_MITIGATION_UCODE_NEEDED] = "Vulnerable: Clear CPU buffers attempted, no microcode", 428 [MMIO_MITIGATION_VERW] = "Mitigation: Clear CPU buffers", 429 }; 430 431 static void __init mmio_select_mitigation(void) 432 { 433 u64 ia32_cap; 434 435 if (!boot_cpu_has_bug(X86_BUG_MMIO_STALE_DATA) || 436 cpu_mitigations_off()) { 437 mmio_mitigation = MMIO_MITIGATION_OFF; 438 return; 439 } 440 441 if (mmio_mitigation == MMIO_MITIGATION_OFF) 442 return; 443 444 ia32_cap = x86_read_arch_cap_msr(); 445 446 /* 447 * Enable CPU buffer clear mitigation for host and VMM, if also affected 448 * by MDS or TAA. Otherwise, enable mitigation for VMM only. 449 */ 450 if (boot_cpu_has_bug(X86_BUG_MDS) || (boot_cpu_has_bug(X86_BUG_TAA) && 451 boot_cpu_has(X86_FEATURE_RTM))) 452 static_branch_enable(&mds_user_clear); 453 else 454 static_branch_enable(&mmio_stale_data_clear); 455 456 /* 457 * If Processor-MMIO-Stale-Data bug is present and Fill Buffer data can 458 * be propagated to uncore buffers, clearing the Fill buffers on idle 459 * is required irrespective of SMT state. 460 */ 461 if (!(ia32_cap & ARCH_CAP_FBSDP_NO)) 462 static_branch_enable(&mds_idle_clear); 463 464 /* 465 * Check if the system has the right microcode. 466 * 467 * CPU Fill buffer clear mitigation is enumerated by either an explicit 468 * FB_CLEAR or by the presence of both MD_CLEAR and L1D_FLUSH on MDS 469 * affected systems. 470 */ 471 if ((ia32_cap & ARCH_CAP_FB_CLEAR) || 472 (boot_cpu_has(X86_FEATURE_MD_CLEAR) && 473 boot_cpu_has(X86_FEATURE_FLUSH_L1D) && 474 !(ia32_cap & ARCH_CAP_MDS_NO))) 475 mmio_mitigation = MMIO_MITIGATION_VERW; 476 else 477 mmio_mitigation = MMIO_MITIGATION_UCODE_NEEDED; 478 479 if (mmio_nosmt || cpu_mitigations_auto_nosmt()) 480 cpu_smt_disable(false); 481 } 482 483 static int __init mmio_stale_data_parse_cmdline(char *str) 484 { 485 if (!boot_cpu_has_bug(X86_BUG_MMIO_STALE_DATA)) 486 return 0; 487 488 if (!str) 489 return -EINVAL; 490 491 if (!strcmp(str, "off")) { 492 mmio_mitigation = MMIO_MITIGATION_OFF; 493 } else if (!strcmp(str, "full")) { 494 mmio_mitigation = MMIO_MITIGATION_VERW; 495 } else if (!strcmp(str, "full,nosmt")) { 496 mmio_mitigation = MMIO_MITIGATION_VERW; 497 mmio_nosmt = true; 498 } 499 500 return 0; 501 } 502 early_param("mmio_stale_data", mmio_stale_data_parse_cmdline); 503 504 #undef pr_fmt 505 #define pr_fmt(fmt) "" fmt 506 507 static void __init md_clear_update_mitigation(void) 508 { 509 if (cpu_mitigations_off()) 510 return; 511 512 if (!static_key_enabled(&mds_user_clear)) 513 goto out; 514 515 /* 516 * mds_user_clear is now enabled. Update MDS, TAA and MMIO Stale Data 517 * mitigation, if necessary. 518 */ 519 if (mds_mitigation == MDS_MITIGATION_OFF && 520 boot_cpu_has_bug(X86_BUG_MDS)) { 521 mds_mitigation = MDS_MITIGATION_FULL; 522 mds_select_mitigation(); 523 } 524 if (taa_mitigation == TAA_MITIGATION_OFF && 525 boot_cpu_has_bug(X86_BUG_TAA)) { 526 taa_mitigation = TAA_MITIGATION_VERW; 527 taa_select_mitigation(); 528 } 529 if (mmio_mitigation == MMIO_MITIGATION_OFF && 530 boot_cpu_has_bug(X86_BUG_MMIO_STALE_DATA)) { 531 mmio_mitigation = MMIO_MITIGATION_VERW; 532 mmio_select_mitigation(); 533 } 534 out: 535 if (boot_cpu_has_bug(X86_BUG_MDS)) 536 pr_info("MDS: %s\n", mds_strings[mds_mitigation]); 537 if (boot_cpu_has_bug(X86_BUG_TAA)) 538 pr_info("TAA: %s\n", taa_strings[taa_mitigation]); 539 if (boot_cpu_has_bug(X86_BUG_MMIO_STALE_DATA)) 540 pr_info("MMIO Stale Data: %s\n", mmio_strings[mmio_mitigation]); 541 } 542 543 static void __init md_clear_select_mitigation(void) 544 { 545 mds_select_mitigation(); 546 taa_select_mitigation(); 547 mmio_select_mitigation(); 548 549 /* 550 * As MDS, TAA and MMIO Stale Data mitigations are inter-related, update 551 * and print their mitigation after MDS, TAA and MMIO Stale Data 552 * mitigation selection is done. 553 */ 554 md_clear_update_mitigation(); 555 } 556 557 #undef pr_fmt 558 #define pr_fmt(fmt) "SRBDS: " fmt 559 560 enum srbds_mitigations { 561 SRBDS_MITIGATION_OFF, 562 SRBDS_MITIGATION_UCODE_NEEDED, 563 SRBDS_MITIGATION_FULL, 564 SRBDS_MITIGATION_TSX_OFF, 565 SRBDS_MITIGATION_HYPERVISOR, 566 }; 567 568 static enum srbds_mitigations srbds_mitigation __ro_after_init = SRBDS_MITIGATION_FULL; 569 570 static const char * const srbds_strings[] = { 571 [SRBDS_MITIGATION_OFF] = "Vulnerable", 572 [SRBDS_MITIGATION_UCODE_NEEDED] = "Vulnerable: No microcode", 573 [SRBDS_MITIGATION_FULL] = "Mitigation: Microcode", 574 [SRBDS_MITIGATION_TSX_OFF] = "Mitigation: TSX disabled", 575 [SRBDS_MITIGATION_HYPERVISOR] = "Unknown: Dependent on hypervisor status", 576 }; 577 578 static bool srbds_off; 579 580 void update_srbds_msr(void) 581 { 582 u64 mcu_ctrl; 583 584 if (!boot_cpu_has_bug(X86_BUG_SRBDS)) 585 return; 586 587 if (boot_cpu_has(X86_FEATURE_HYPERVISOR)) 588 return; 589 590 if (srbds_mitigation == SRBDS_MITIGATION_UCODE_NEEDED) 591 return; 592 593 /* 594 * A MDS_NO CPU for which SRBDS mitigation is not needed due to TSX 595 * being disabled and it hasn't received the SRBDS MSR microcode. 596 */ 597 if (!boot_cpu_has(X86_FEATURE_SRBDS_CTRL)) 598 return; 599 600 rdmsrl(MSR_IA32_MCU_OPT_CTRL, mcu_ctrl); 601 602 switch (srbds_mitigation) { 603 case SRBDS_MITIGATION_OFF: 604 case SRBDS_MITIGATION_TSX_OFF: 605 mcu_ctrl |= RNGDS_MITG_DIS; 606 break; 607 case SRBDS_MITIGATION_FULL: 608 mcu_ctrl &= ~RNGDS_MITG_DIS; 609 break; 610 default: 611 break; 612 } 613 614 wrmsrl(MSR_IA32_MCU_OPT_CTRL, mcu_ctrl); 615 } 616 617 static void __init srbds_select_mitigation(void) 618 { 619 u64 ia32_cap; 620 621 if (!boot_cpu_has_bug(X86_BUG_SRBDS)) 622 return; 623 624 /* 625 * Check to see if this is one of the MDS_NO systems supporting TSX that 626 * are only exposed to SRBDS when TSX is enabled or when CPU is affected 627 * by Processor MMIO Stale Data vulnerability. 628 */ 629 ia32_cap = x86_read_arch_cap_msr(); 630 if ((ia32_cap & ARCH_CAP_MDS_NO) && !boot_cpu_has(X86_FEATURE_RTM) && 631 !boot_cpu_has_bug(X86_BUG_MMIO_STALE_DATA)) 632 srbds_mitigation = SRBDS_MITIGATION_TSX_OFF; 633 else if (boot_cpu_has(X86_FEATURE_HYPERVISOR)) 634 srbds_mitigation = SRBDS_MITIGATION_HYPERVISOR; 635 else if (!boot_cpu_has(X86_FEATURE_SRBDS_CTRL)) 636 srbds_mitigation = SRBDS_MITIGATION_UCODE_NEEDED; 637 else if (cpu_mitigations_off() || srbds_off) 638 srbds_mitigation = SRBDS_MITIGATION_OFF; 639 640 update_srbds_msr(); 641 pr_info("%s\n", srbds_strings[srbds_mitigation]); 642 } 643 644 static int __init srbds_parse_cmdline(char *str) 645 { 646 if (!str) 647 return -EINVAL; 648 649 if (!boot_cpu_has_bug(X86_BUG_SRBDS)) 650 return 0; 651 652 srbds_off = !strcmp(str, "off"); 653 return 0; 654 } 655 early_param("srbds", srbds_parse_cmdline); 656 657 #undef pr_fmt 658 #define pr_fmt(fmt) "L1D Flush : " fmt 659 660 enum l1d_flush_mitigations { 661 L1D_FLUSH_OFF = 0, 662 L1D_FLUSH_ON, 663 }; 664 665 static enum l1d_flush_mitigations l1d_flush_mitigation __initdata = L1D_FLUSH_OFF; 666 667 static void __init l1d_flush_select_mitigation(void) 668 { 669 if (!l1d_flush_mitigation || !boot_cpu_has(X86_FEATURE_FLUSH_L1D)) 670 return; 671 672 static_branch_enable(&switch_mm_cond_l1d_flush); 673 pr_info("Conditional flush on switch_mm() enabled\n"); 674 } 675 676 static int __init l1d_flush_parse_cmdline(char *str) 677 { 678 if (!strcmp(str, "on")) 679 l1d_flush_mitigation = L1D_FLUSH_ON; 680 681 return 0; 682 } 683 early_param("l1d_flush", l1d_flush_parse_cmdline); 684 685 #undef pr_fmt 686 #define pr_fmt(fmt) "Spectre V1 : " fmt 687 688 enum spectre_v1_mitigation { 689 SPECTRE_V1_MITIGATION_NONE, 690 SPECTRE_V1_MITIGATION_AUTO, 691 }; 692 693 static enum spectre_v1_mitigation spectre_v1_mitigation __ro_after_init = 694 SPECTRE_V1_MITIGATION_AUTO; 695 696 static const char * const spectre_v1_strings[] = { 697 [SPECTRE_V1_MITIGATION_NONE] = "Vulnerable: __user pointer sanitization and usercopy barriers only; no swapgs barriers", 698 [SPECTRE_V1_MITIGATION_AUTO] = "Mitigation: usercopy/swapgs barriers and __user pointer sanitization", 699 }; 700 701 /* 702 * Does SMAP provide full mitigation against speculative kernel access to 703 * userspace? 704 */ 705 static bool smap_works_speculatively(void) 706 { 707 if (!boot_cpu_has(X86_FEATURE_SMAP)) 708 return false; 709 710 /* 711 * On CPUs which are vulnerable to Meltdown, SMAP does not 712 * prevent speculative access to user data in the L1 cache. 713 * Consider SMAP to be non-functional as a mitigation on these 714 * CPUs. 715 */ 716 if (boot_cpu_has(X86_BUG_CPU_MELTDOWN)) 717 return false; 718 719 return true; 720 } 721 722 static void __init spectre_v1_select_mitigation(void) 723 { 724 if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V1) || cpu_mitigations_off()) { 725 spectre_v1_mitigation = SPECTRE_V1_MITIGATION_NONE; 726 return; 727 } 728 729 if (spectre_v1_mitigation == SPECTRE_V1_MITIGATION_AUTO) { 730 /* 731 * With Spectre v1, a user can speculatively control either 732 * path of a conditional swapgs with a user-controlled GS 733 * value. The mitigation is to add lfences to both code paths. 734 * 735 * If FSGSBASE is enabled, the user can put a kernel address in 736 * GS, in which case SMAP provides no protection. 737 * 738 * If FSGSBASE is disabled, the user can only put a user space 739 * address in GS. That makes an attack harder, but still 740 * possible if there's no SMAP protection. 741 */ 742 if (boot_cpu_has(X86_FEATURE_FSGSBASE) || 743 !smap_works_speculatively()) { 744 /* 745 * Mitigation can be provided from SWAPGS itself or 746 * PTI as the CR3 write in the Meltdown mitigation 747 * is serializing. 748 * 749 * If neither is there, mitigate with an LFENCE to 750 * stop speculation through swapgs. 751 */ 752 if (boot_cpu_has_bug(X86_BUG_SWAPGS) && 753 !boot_cpu_has(X86_FEATURE_PTI)) 754 setup_force_cpu_cap(X86_FEATURE_FENCE_SWAPGS_USER); 755 756 /* 757 * Enable lfences in the kernel entry (non-swapgs) 758 * paths, to prevent user entry from speculatively 759 * skipping swapgs. 760 */ 761 setup_force_cpu_cap(X86_FEATURE_FENCE_SWAPGS_KERNEL); 762 } 763 } 764 765 pr_info("%s\n", spectre_v1_strings[spectre_v1_mitigation]); 766 } 767 768 static int __init nospectre_v1_cmdline(char *str) 769 { 770 spectre_v1_mitigation = SPECTRE_V1_MITIGATION_NONE; 771 return 0; 772 } 773 early_param("nospectre_v1", nospectre_v1_cmdline); 774 775 static enum spectre_v2_mitigation spectre_v2_enabled __ro_after_init = 776 SPECTRE_V2_NONE; 777 778 #undef pr_fmt 779 #define pr_fmt(fmt) "RETBleed: " fmt 780 781 enum retbleed_mitigation { 782 RETBLEED_MITIGATION_NONE, 783 RETBLEED_MITIGATION_UNRET, 784 RETBLEED_MITIGATION_IBPB, 785 RETBLEED_MITIGATION_IBRS, 786 RETBLEED_MITIGATION_EIBRS, 787 }; 788 789 enum retbleed_mitigation_cmd { 790 RETBLEED_CMD_OFF, 791 RETBLEED_CMD_AUTO, 792 RETBLEED_CMD_UNRET, 793 RETBLEED_CMD_IBPB, 794 }; 795 796 static const char * const retbleed_strings[] = { 797 [RETBLEED_MITIGATION_NONE] = "Vulnerable", 798 [RETBLEED_MITIGATION_UNRET] = "Mitigation: untrained return thunk", 799 [RETBLEED_MITIGATION_IBPB] = "Mitigation: IBPB", 800 [RETBLEED_MITIGATION_IBRS] = "Mitigation: IBRS", 801 [RETBLEED_MITIGATION_EIBRS] = "Mitigation: Enhanced IBRS", 802 }; 803 804 static enum retbleed_mitigation retbleed_mitigation __ro_after_init = 805 RETBLEED_MITIGATION_NONE; 806 static enum retbleed_mitigation_cmd retbleed_cmd __ro_after_init = 807 RETBLEED_CMD_AUTO; 808 809 static int __ro_after_init retbleed_nosmt = false; 810 811 static int __init retbleed_parse_cmdline(char *str) 812 { 813 if (!str) 814 return -EINVAL; 815 816 while (str) { 817 char *next = strchr(str, ','); 818 if (next) { 819 *next = 0; 820 next++; 821 } 822 823 if (!strcmp(str, "off")) { 824 retbleed_cmd = RETBLEED_CMD_OFF; 825 } else if (!strcmp(str, "auto")) { 826 retbleed_cmd = RETBLEED_CMD_AUTO; 827 } else if (!strcmp(str, "unret")) { 828 retbleed_cmd = RETBLEED_CMD_UNRET; 829 } else if (!strcmp(str, "ibpb")) { 830 retbleed_cmd = RETBLEED_CMD_IBPB; 831 } else if (!strcmp(str, "nosmt")) { 832 retbleed_nosmt = true; 833 } else { 834 pr_err("Ignoring unknown retbleed option (%s).", str); 835 } 836 837 str = next; 838 } 839 840 return 0; 841 } 842 early_param("retbleed", retbleed_parse_cmdline); 843 844 #define RETBLEED_UNTRAIN_MSG "WARNING: BTB untrained return thunk mitigation is only effective on AMD/Hygon!\n" 845 #define RETBLEED_INTEL_MSG "WARNING: Spectre v2 mitigation leaves CPU vulnerable to RETBleed attacks, data leaks possible!\n" 846 847 static void __init retbleed_select_mitigation(void) 848 { 849 bool mitigate_smt = false; 850 851 if (!boot_cpu_has_bug(X86_BUG_RETBLEED) || cpu_mitigations_off()) 852 return; 853 854 switch (retbleed_cmd) { 855 case RETBLEED_CMD_OFF: 856 return; 857 858 case RETBLEED_CMD_UNRET: 859 if (IS_ENABLED(CONFIG_CPU_UNRET_ENTRY)) { 860 retbleed_mitigation = RETBLEED_MITIGATION_UNRET; 861 } else { 862 pr_err("WARNING: kernel not compiled with CPU_UNRET_ENTRY.\n"); 863 goto do_cmd_auto; 864 } 865 break; 866 867 case RETBLEED_CMD_IBPB: 868 if (!boot_cpu_has(X86_FEATURE_IBPB)) { 869 pr_err("WARNING: CPU does not support IBPB.\n"); 870 goto do_cmd_auto; 871 } else if (IS_ENABLED(CONFIG_CPU_IBPB_ENTRY)) { 872 retbleed_mitigation = RETBLEED_MITIGATION_IBPB; 873 } else { 874 pr_err("WARNING: kernel not compiled with CPU_IBPB_ENTRY.\n"); 875 goto do_cmd_auto; 876 } 877 break; 878 879 do_cmd_auto: 880 case RETBLEED_CMD_AUTO: 881 default: 882 if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD || 883 boot_cpu_data.x86_vendor == X86_VENDOR_HYGON) { 884 if (IS_ENABLED(CONFIG_CPU_UNRET_ENTRY)) 885 retbleed_mitigation = RETBLEED_MITIGATION_UNRET; 886 else if (IS_ENABLED(CONFIG_CPU_IBPB_ENTRY) && boot_cpu_has(X86_FEATURE_IBPB)) 887 retbleed_mitigation = RETBLEED_MITIGATION_IBPB; 888 } 889 890 /* 891 * The Intel mitigation (IBRS or eIBRS) was already selected in 892 * spectre_v2_select_mitigation(). 'retbleed_mitigation' will 893 * be set accordingly below. 894 */ 895 896 break; 897 } 898 899 switch (retbleed_mitigation) { 900 case RETBLEED_MITIGATION_UNRET: 901 setup_force_cpu_cap(X86_FEATURE_RETHUNK); 902 setup_force_cpu_cap(X86_FEATURE_UNRET); 903 904 if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD && 905 boot_cpu_data.x86_vendor != X86_VENDOR_HYGON) 906 pr_err(RETBLEED_UNTRAIN_MSG); 907 908 mitigate_smt = true; 909 break; 910 911 case RETBLEED_MITIGATION_IBPB: 912 setup_force_cpu_cap(X86_FEATURE_ENTRY_IBPB); 913 mitigate_smt = true; 914 break; 915 916 default: 917 break; 918 } 919 920 if (mitigate_smt && !boot_cpu_has(X86_FEATURE_STIBP) && 921 (retbleed_nosmt || cpu_mitigations_auto_nosmt())) 922 cpu_smt_disable(false); 923 924 /* 925 * Let IBRS trump all on Intel without affecting the effects of the 926 * retbleed= cmdline option. 927 */ 928 if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL) { 929 switch (spectre_v2_enabled) { 930 case SPECTRE_V2_IBRS: 931 retbleed_mitigation = RETBLEED_MITIGATION_IBRS; 932 break; 933 case SPECTRE_V2_EIBRS: 934 case SPECTRE_V2_EIBRS_RETPOLINE: 935 case SPECTRE_V2_EIBRS_LFENCE: 936 retbleed_mitigation = RETBLEED_MITIGATION_EIBRS; 937 break; 938 default: 939 pr_err(RETBLEED_INTEL_MSG); 940 } 941 } 942 943 pr_info("%s\n", retbleed_strings[retbleed_mitigation]); 944 } 945 946 #undef pr_fmt 947 #define pr_fmt(fmt) "Spectre V2 : " fmt 948 949 static enum spectre_v2_user_mitigation spectre_v2_user_stibp __ro_after_init = 950 SPECTRE_V2_USER_NONE; 951 static enum spectre_v2_user_mitigation spectre_v2_user_ibpb __ro_after_init = 952 SPECTRE_V2_USER_NONE; 953 954 #ifdef CONFIG_RETPOLINE 955 static bool spectre_v2_bad_module; 956 957 bool retpoline_module_ok(bool has_retpoline) 958 { 959 if (spectre_v2_enabled == SPECTRE_V2_NONE || has_retpoline) 960 return true; 961 962 pr_err("System may be vulnerable to spectre v2\n"); 963 spectre_v2_bad_module = true; 964 return false; 965 } 966 967 static inline const char *spectre_v2_module_string(void) 968 { 969 return spectre_v2_bad_module ? " - vulnerable module loaded" : ""; 970 } 971 #else 972 static inline const char *spectre_v2_module_string(void) { return ""; } 973 #endif 974 975 #define SPECTRE_V2_LFENCE_MSG "WARNING: LFENCE mitigation is not recommended for this CPU, data leaks possible!\n" 976 #define SPECTRE_V2_EIBRS_EBPF_MSG "WARNING: Unprivileged eBPF is enabled with eIBRS on, data leaks possible via Spectre v2 BHB attacks!\n" 977 #define SPECTRE_V2_EIBRS_LFENCE_EBPF_SMT_MSG "WARNING: Unprivileged eBPF is enabled with eIBRS+LFENCE mitigation and SMT, data leaks possible via Spectre v2 BHB attacks!\n" 978 #define SPECTRE_V2_IBRS_PERF_MSG "WARNING: IBRS mitigation selected on Enhanced IBRS CPU, this may cause unnecessary performance loss\n" 979 980 #ifdef CONFIG_BPF_SYSCALL 981 void unpriv_ebpf_notify(int new_state) 982 { 983 if (new_state) 984 return; 985 986 /* Unprivileged eBPF is enabled */ 987 988 switch (spectre_v2_enabled) { 989 case SPECTRE_V2_EIBRS: 990 pr_err(SPECTRE_V2_EIBRS_EBPF_MSG); 991 break; 992 case SPECTRE_V2_EIBRS_LFENCE: 993 if (sched_smt_active()) 994 pr_err(SPECTRE_V2_EIBRS_LFENCE_EBPF_SMT_MSG); 995 break; 996 default: 997 break; 998 } 999 } 1000 #endif 1001 1002 static inline bool match_option(const char *arg, int arglen, const char *opt) 1003 { 1004 int len = strlen(opt); 1005 1006 return len == arglen && !strncmp(arg, opt, len); 1007 } 1008 1009 /* The kernel command line selection for spectre v2 */ 1010 enum spectre_v2_mitigation_cmd { 1011 SPECTRE_V2_CMD_NONE, 1012 SPECTRE_V2_CMD_AUTO, 1013 SPECTRE_V2_CMD_FORCE, 1014 SPECTRE_V2_CMD_RETPOLINE, 1015 SPECTRE_V2_CMD_RETPOLINE_GENERIC, 1016 SPECTRE_V2_CMD_RETPOLINE_LFENCE, 1017 SPECTRE_V2_CMD_EIBRS, 1018 SPECTRE_V2_CMD_EIBRS_RETPOLINE, 1019 SPECTRE_V2_CMD_EIBRS_LFENCE, 1020 SPECTRE_V2_CMD_IBRS, 1021 }; 1022 1023 enum spectre_v2_user_cmd { 1024 SPECTRE_V2_USER_CMD_NONE, 1025 SPECTRE_V2_USER_CMD_AUTO, 1026 SPECTRE_V2_USER_CMD_FORCE, 1027 SPECTRE_V2_USER_CMD_PRCTL, 1028 SPECTRE_V2_USER_CMD_PRCTL_IBPB, 1029 SPECTRE_V2_USER_CMD_SECCOMP, 1030 SPECTRE_V2_USER_CMD_SECCOMP_IBPB, 1031 }; 1032 1033 static const char * const spectre_v2_user_strings[] = { 1034 [SPECTRE_V2_USER_NONE] = "User space: Vulnerable", 1035 [SPECTRE_V2_USER_STRICT] = "User space: Mitigation: STIBP protection", 1036 [SPECTRE_V2_USER_STRICT_PREFERRED] = "User space: Mitigation: STIBP always-on protection", 1037 [SPECTRE_V2_USER_PRCTL] = "User space: Mitigation: STIBP via prctl", 1038 [SPECTRE_V2_USER_SECCOMP] = "User space: Mitigation: STIBP via seccomp and prctl", 1039 }; 1040 1041 static const struct { 1042 const char *option; 1043 enum spectre_v2_user_cmd cmd; 1044 bool secure; 1045 } v2_user_options[] __initconst = { 1046 { "auto", SPECTRE_V2_USER_CMD_AUTO, false }, 1047 { "off", SPECTRE_V2_USER_CMD_NONE, false }, 1048 { "on", SPECTRE_V2_USER_CMD_FORCE, true }, 1049 { "prctl", SPECTRE_V2_USER_CMD_PRCTL, false }, 1050 { "prctl,ibpb", SPECTRE_V2_USER_CMD_PRCTL_IBPB, false }, 1051 { "seccomp", SPECTRE_V2_USER_CMD_SECCOMP, false }, 1052 { "seccomp,ibpb", SPECTRE_V2_USER_CMD_SECCOMP_IBPB, false }, 1053 }; 1054 1055 static void __init spec_v2_user_print_cond(const char *reason, bool secure) 1056 { 1057 if (boot_cpu_has_bug(X86_BUG_SPECTRE_V2) != secure) 1058 pr_info("spectre_v2_user=%s forced on command line.\n", reason); 1059 } 1060 1061 static __ro_after_init enum spectre_v2_mitigation_cmd spectre_v2_cmd; 1062 1063 static enum spectre_v2_user_cmd __init 1064 spectre_v2_parse_user_cmdline(void) 1065 { 1066 char arg[20]; 1067 int ret, i; 1068 1069 switch (spectre_v2_cmd) { 1070 case SPECTRE_V2_CMD_NONE: 1071 return SPECTRE_V2_USER_CMD_NONE; 1072 case SPECTRE_V2_CMD_FORCE: 1073 return SPECTRE_V2_USER_CMD_FORCE; 1074 default: 1075 break; 1076 } 1077 1078 ret = cmdline_find_option(boot_command_line, "spectre_v2_user", 1079 arg, sizeof(arg)); 1080 if (ret < 0) 1081 return SPECTRE_V2_USER_CMD_AUTO; 1082 1083 for (i = 0; i < ARRAY_SIZE(v2_user_options); i++) { 1084 if (match_option(arg, ret, v2_user_options[i].option)) { 1085 spec_v2_user_print_cond(v2_user_options[i].option, 1086 v2_user_options[i].secure); 1087 return v2_user_options[i].cmd; 1088 } 1089 } 1090 1091 pr_err("Unknown user space protection option (%s). Switching to AUTO select\n", arg); 1092 return SPECTRE_V2_USER_CMD_AUTO; 1093 } 1094 1095 static inline bool spectre_v2_in_ibrs_mode(enum spectre_v2_mitigation mode) 1096 { 1097 return mode == SPECTRE_V2_IBRS || 1098 mode == SPECTRE_V2_EIBRS || 1099 mode == SPECTRE_V2_EIBRS_RETPOLINE || 1100 mode == SPECTRE_V2_EIBRS_LFENCE; 1101 } 1102 1103 static void __init 1104 spectre_v2_user_select_mitigation(void) 1105 { 1106 enum spectre_v2_user_mitigation mode = SPECTRE_V2_USER_NONE; 1107 bool smt_possible = IS_ENABLED(CONFIG_SMP); 1108 enum spectre_v2_user_cmd cmd; 1109 1110 if (!boot_cpu_has(X86_FEATURE_IBPB) && !boot_cpu_has(X86_FEATURE_STIBP)) 1111 return; 1112 1113 if (cpu_smt_control == CPU_SMT_FORCE_DISABLED || 1114 cpu_smt_control == CPU_SMT_NOT_SUPPORTED) 1115 smt_possible = false; 1116 1117 cmd = spectre_v2_parse_user_cmdline(); 1118 switch (cmd) { 1119 case SPECTRE_V2_USER_CMD_NONE: 1120 goto set_mode; 1121 case SPECTRE_V2_USER_CMD_FORCE: 1122 mode = SPECTRE_V2_USER_STRICT; 1123 break; 1124 case SPECTRE_V2_USER_CMD_AUTO: 1125 case SPECTRE_V2_USER_CMD_PRCTL: 1126 case SPECTRE_V2_USER_CMD_PRCTL_IBPB: 1127 mode = SPECTRE_V2_USER_PRCTL; 1128 break; 1129 case SPECTRE_V2_USER_CMD_SECCOMP: 1130 case SPECTRE_V2_USER_CMD_SECCOMP_IBPB: 1131 if (IS_ENABLED(CONFIG_SECCOMP)) 1132 mode = SPECTRE_V2_USER_SECCOMP; 1133 else 1134 mode = SPECTRE_V2_USER_PRCTL; 1135 break; 1136 } 1137 1138 /* Initialize Indirect Branch Prediction Barrier */ 1139 if (boot_cpu_has(X86_FEATURE_IBPB)) { 1140 setup_force_cpu_cap(X86_FEATURE_USE_IBPB); 1141 1142 spectre_v2_user_ibpb = mode; 1143 switch (cmd) { 1144 case SPECTRE_V2_USER_CMD_FORCE: 1145 case SPECTRE_V2_USER_CMD_PRCTL_IBPB: 1146 case SPECTRE_V2_USER_CMD_SECCOMP_IBPB: 1147 static_branch_enable(&switch_mm_always_ibpb); 1148 spectre_v2_user_ibpb = SPECTRE_V2_USER_STRICT; 1149 break; 1150 case SPECTRE_V2_USER_CMD_PRCTL: 1151 case SPECTRE_V2_USER_CMD_AUTO: 1152 case SPECTRE_V2_USER_CMD_SECCOMP: 1153 static_branch_enable(&switch_mm_cond_ibpb); 1154 break; 1155 default: 1156 break; 1157 } 1158 1159 pr_info("mitigation: Enabling %s Indirect Branch Prediction Barrier\n", 1160 static_key_enabled(&switch_mm_always_ibpb) ? 1161 "always-on" : "conditional"); 1162 } 1163 1164 /* 1165 * If no STIBP, IBRS or enhanced IBRS is enabled, or SMT impossible, 1166 * STIBP is not required. 1167 */ 1168 if (!boot_cpu_has(X86_FEATURE_STIBP) || 1169 !smt_possible || 1170 spectre_v2_in_ibrs_mode(spectre_v2_enabled)) 1171 return; 1172 1173 /* 1174 * At this point, an STIBP mode other than "off" has been set. 1175 * If STIBP support is not being forced, check if STIBP always-on 1176 * is preferred. 1177 */ 1178 if (mode != SPECTRE_V2_USER_STRICT && 1179 boot_cpu_has(X86_FEATURE_AMD_STIBP_ALWAYS_ON)) 1180 mode = SPECTRE_V2_USER_STRICT_PREFERRED; 1181 1182 if (retbleed_mitigation == RETBLEED_MITIGATION_UNRET) { 1183 if (mode != SPECTRE_V2_USER_STRICT && 1184 mode != SPECTRE_V2_USER_STRICT_PREFERRED) 1185 pr_info("Selecting STIBP always-on mode to complement retbleed mitigation\n"); 1186 mode = SPECTRE_V2_USER_STRICT_PREFERRED; 1187 } 1188 1189 spectre_v2_user_stibp = mode; 1190 1191 set_mode: 1192 pr_info("%s\n", spectre_v2_user_strings[mode]); 1193 } 1194 1195 static const char * const spectre_v2_strings[] = { 1196 [SPECTRE_V2_NONE] = "Vulnerable", 1197 [SPECTRE_V2_RETPOLINE] = "Mitigation: Retpolines", 1198 [SPECTRE_V2_LFENCE] = "Mitigation: LFENCE", 1199 [SPECTRE_V2_EIBRS] = "Mitigation: Enhanced IBRS", 1200 [SPECTRE_V2_EIBRS_LFENCE] = "Mitigation: Enhanced IBRS + LFENCE", 1201 [SPECTRE_V2_EIBRS_RETPOLINE] = "Mitigation: Enhanced IBRS + Retpolines", 1202 [SPECTRE_V2_IBRS] = "Mitigation: IBRS", 1203 }; 1204 1205 static const struct { 1206 const char *option; 1207 enum spectre_v2_mitigation_cmd cmd; 1208 bool secure; 1209 } mitigation_options[] __initconst = { 1210 { "off", SPECTRE_V2_CMD_NONE, false }, 1211 { "on", SPECTRE_V2_CMD_FORCE, true }, 1212 { "retpoline", SPECTRE_V2_CMD_RETPOLINE, false }, 1213 { "retpoline,amd", SPECTRE_V2_CMD_RETPOLINE_LFENCE, false }, 1214 { "retpoline,lfence", SPECTRE_V2_CMD_RETPOLINE_LFENCE, false }, 1215 { "retpoline,generic", SPECTRE_V2_CMD_RETPOLINE_GENERIC, false }, 1216 { "eibrs", SPECTRE_V2_CMD_EIBRS, false }, 1217 { "eibrs,lfence", SPECTRE_V2_CMD_EIBRS_LFENCE, false }, 1218 { "eibrs,retpoline", SPECTRE_V2_CMD_EIBRS_RETPOLINE, false }, 1219 { "auto", SPECTRE_V2_CMD_AUTO, false }, 1220 { "ibrs", SPECTRE_V2_CMD_IBRS, false }, 1221 }; 1222 1223 static void __init spec_v2_print_cond(const char *reason, bool secure) 1224 { 1225 if (boot_cpu_has_bug(X86_BUG_SPECTRE_V2) != secure) 1226 pr_info("%s selected on command line.\n", reason); 1227 } 1228 1229 static enum spectre_v2_mitigation_cmd __init spectre_v2_parse_cmdline(void) 1230 { 1231 enum spectre_v2_mitigation_cmd cmd = SPECTRE_V2_CMD_AUTO; 1232 char arg[20]; 1233 int ret, i; 1234 1235 if (cmdline_find_option_bool(boot_command_line, "nospectre_v2") || 1236 cpu_mitigations_off()) 1237 return SPECTRE_V2_CMD_NONE; 1238 1239 ret = cmdline_find_option(boot_command_line, "spectre_v2", arg, sizeof(arg)); 1240 if (ret < 0) 1241 return SPECTRE_V2_CMD_AUTO; 1242 1243 for (i = 0; i < ARRAY_SIZE(mitigation_options); i++) { 1244 if (!match_option(arg, ret, mitigation_options[i].option)) 1245 continue; 1246 cmd = mitigation_options[i].cmd; 1247 break; 1248 } 1249 1250 if (i >= ARRAY_SIZE(mitigation_options)) { 1251 pr_err("unknown option (%s). Switching to AUTO select\n", arg); 1252 return SPECTRE_V2_CMD_AUTO; 1253 } 1254 1255 if ((cmd == SPECTRE_V2_CMD_RETPOLINE || 1256 cmd == SPECTRE_V2_CMD_RETPOLINE_LFENCE || 1257 cmd == SPECTRE_V2_CMD_RETPOLINE_GENERIC || 1258 cmd == SPECTRE_V2_CMD_EIBRS_LFENCE || 1259 cmd == SPECTRE_V2_CMD_EIBRS_RETPOLINE) && 1260 !IS_ENABLED(CONFIG_RETPOLINE)) { 1261 pr_err("%s selected but not compiled in. Switching to AUTO select\n", 1262 mitigation_options[i].option); 1263 return SPECTRE_V2_CMD_AUTO; 1264 } 1265 1266 if ((cmd == SPECTRE_V2_CMD_EIBRS || 1267 cmd == SPECTRE_V2_CMD_EIBRS_LFENCE || 1268 cmd == SPECTRE_V2_CMD_EIBRS_RETPOLINE) && 1269 !boot_cpu_has(X86_FEATURE_IBRS_ENHANCED)) { 1270 pr_err("%s selected but CPU doesn't have eIBRS. Switching to AUTO select\n", 1271 mitigation_options[i].option); 1272 return SPECTRE_V2_CMD_AUTO; 1273 } 1274 1275 if ((cmd == SPECTRE_V2_CMD_RETPOLINE_LFENCE || 1276 cmd == SPECTRE_V2_CMD_EIBRS_LFENCE) && 1277 !boot_cpu_has(X86_FEATURE_LFENCE_RDTSC)) { 1278 pr_err("%s selected, but CPU doesn't have a serializing LFENCE. Switching to AUTO select\n", 1279 mitigation_options[i].option); 1280 return SPECTRE_V2_CMD_AUTO; 1281 } 1282 1283 if (cmd == SPECTRE_V2_CMD_IBRS && !IS_ENABLED(CONFIG_CPU_IBRS_ENTRY)) { 1284 pr_err("%s selected but not compiled in. Switching to AUTO select\n", 1285 mitigation_options[i].option); 1286 return SPECTRE_V2_CMD_AUTO; 1287 } 1288 1289 if (cmd == SPECTRE_V2_CMD_IBRS && boot_cpu_data.x86_vendor != X86_VENDOR_INTEL) { 1290 pr_err("%s selected but not Intel CPU. Switching to AUTO select\n", 1291 mitigation_options[i].option); 1292 return SPECTRE_V2_CMD_AUTO; 1293 } 1294 1295 if (cmd == SPECTRE_V2_CMD_IBRS && !boot_cpu_has(X86_FEATURE_IBRS)) { 1296 pr_err("%s selected but CPU doesn't have IBRS. Switching to AUTO select\n", 1297 mitigation_options[i].option); 1298 return SPECTRE_V2_CMD_AUTO; 1299 } 1300 1301 if (cmd == SPECTRE_V2_CMD_IBRS && boot_cpu_has(X86_FEATURE_XENPV)) { 1302 pr_err("%s selected but running as XenPV guest. Switching to AUTO select\n", 1303 mitigation_options[i].option); 1304 return SPECTRE_V2_CMD_AUTO; 1305 } 1306 1307 spec_v2_print_cond(mitigation_options[i].option, 1308 mitigation_options[i].secure); 1309 return cmd; 1310 } 1311 1312 static enum spectre_v2_mitigation __init spectre_v2_select_retpoline(void) 1313 { 1314 if (!IS_ENABLED(CONFIG_RETPOLINE)) { 1315 pr_err("Kernel not compiled with retpoline; no mitigation available!"); 1316 return SPECTRE_V2_NONE; 1317 } 1318 1319 return SPECTRE_V2_RETPOLINE; 1320 } 1321 1322 /* Disable in-kernel use of non-RSB RET predictors */ 1323 static void __init spec_ctrl_disable_kernel_rrsba(void) 1324 { 1325 u64 ia32_cap; 1326 1327 if (!boot_cpu_has(X86_FEATURE_RRSBA_CTRL)) 1328 return; 1329 1330 ia32_cap = x86_read_arch_cap_msr(); 1331 1332 if (ia32_cap & ARCH_CAP_RRSBA) { 1333 x86_spec_ctrl_base |= SPEC_CTRL_RRSBA_DIS_S; 1334 write_spec_ctrl_current(x86_spec_ctrl_base, true); 1335 } 1336 } 1337 1338 static void __init spectre_v2_determine_rsb_fill_type_at_vmexit(enum spectre_v2_mitigation mode) 1339 { 1340 /* 1341 * Similar to context switches, there are two types of RSB attacks 1342 * after VM exit: 1343 * 1344 * 1) RSB underflow 1345 * 1346 * 2) Poisoned RSB entry 1347 * 1348 * When retpoline is enabled, both are mitigated by filling/clearing 1349 * the RSB. 1350 * 1351 * When IBRS is enabled, while #1 would be mitigated by the IBRS branch 1352 * prediction isolation protections, RSB still needs to be cleared 1353 * because of #2. Note that SMEP provides no protection here, unlike 1354 * user-space-poisoned RSB entries. 1355 * 1356 * eIBRS should protect against RSB poisoning, but if the EIBRS_PBRSB 1357 * bug is present then a LITE version of RSB protection is required, 1358 * just a single call needs to retire before a RET is executed. 1359 */ 1360 switch (mode) { 1361 case SPECTRE_V2_NONE: 1362 return; 1363 1364 case SPECTRE_V2_EIBRS_LFENCE: 1365 case SPECTRE_V2_EIBRS: 1366 if (boot_cpu_has_bug(X86_BUG_EIBRS_PBRSB)) { 1367 setup_force_cpu_cap(X86_FEATURE_RSB_VMEXIT_LITE); 1368 pr_info("Spectre v2 / PBRSB-eIBRS: Retire a single CALL on VMEXIT\n"); 1369 } 1370 return; 1371 1372 case SPECTRE_V2_EIBRS_RETPOLINE: 1373 case SPECTRE_V2_RETPOLINE: 1374 case SPECTRE_V2_LFENCE: 1375 case SPECTRE_V2_IBRS: 1376 setup_force_cpu_cap(X86_FEATURE_RSB_VMEXIT); 1377 pr_info("Spectre v2 / SpectreRSB : Filling RSB on VMEXIT\n"); 1378 return; 1379 } 1380 1381 pr_warn_once("Unknown Spectre v2 mode, disabling RSB mitigation at VM exit"); 1382 dump_stack(); 1383 } 1384 1385 static void __init spectre_v2_select_mitigation(void) 1386 { 1387 enum spectre_v2_mitigation_cmd cmd = spectre_v2_parse_cmdline(); 1388 enum spectre_v2_mitigation mode = SPECTRE_V2_NONE; 1389 1390 /* 1391 * If the CPU is not affected and the command line mode is NONE or AUTO 1392 * then nothing to do. 1393 */ 1394 if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V2) && 1395 (cmd == SPECTRE_V2_CMD_NONE || cmd == SPECTRE_V2_CMD_AUTO)) 1396 return; 1397 1398 switch (cmd) { 1399 case SPECTRE_V2_CMD_NONE: 1400 return; 1401 1402 case SPECTRE_V2_CMD_FORCE: 1403 case SPECTRE_V2_CMD_AUTO: 1404 if (boot_cpu_has(X86_FEATURE_IBRS_ENHANCED)) { 1405 mode = SPECTRE_V2_EIBRS; 1406 break; 1407 } 1408 1409 if (IS_ENABLED(CONFIG_CPU_IBRS_ENTRY) && 1410 boot_cpu_has_bug(X86_BUG_RETBLEED) && 1411 retbleed_cmd != RETBLEED_CMD_OFF && 1412 boot_cpu_has(X86_FEATURE_IBRS) && 1413 boot_cpu_data.x86_vendor == X86_VENDOR_INTEL) { 1414 mode = SPECTRE_V2_IBRS; 1415 break; 1416 } 1417 1418 mode = spectre_v2_select_retpoline(); 1419 break; 1420 1421 case SPECTRE_V2_CMD_RETPOLINE_LFENCE: 1422 pr_err(SPECTRE_V2_LFENCE_MSG); 1423 mode = SPECTRE_V2_LFENCE; 1424 break; 1425 1426 case SPECTRE_V2_CMD_RETPOLINE_GENERIC: 1427 mode = SPECTRE_V2_RETPOLINE; 1428 break; 1429 1430 case SPECTRE_V2_CMD_RETPOLINE: 1431 mode = spectre_v2_select_retpoline(); 1432 break; 1433 1434 case SPECTRE_V2_CMD_IBRS: 1435 mode = SPECTRE_V2_IBRS; 1436 break; 1437 1438 case SPECTRE_V2_CMD_EIBRS: 1439 mode = SPECTRE_V2_EIBRS; 1440 break; 1441 1442 case SPECTRE_V2_CMD_EIBRS_LFENCE: 1443 mode = SPECTRE_V2_EIBRS_LFENCE; 1444 break; 1445 1446 case SPECTRE_V2_CMD_EIBRS_RETPOLINE: 1447 mode = SPECTRE_V2_EIBRS_RETPOLINE; 1448 break; 1449 } 1450 1451 if (mode == SPECTRE_V2_EIBRS && unprivileged_ebpf_enabled()) 1452 pr_err(SPECTRE_V2_EIBRS_EBPF_MSG); 1453 1454 if (spectre_v2_in_ibrs_mode(mode)) { 1455 x86_spec_ctrl_base |= SPEC_CTRL_IBRS; 1456 write_spec_ctrl_current(x86_spec_ctrl_base, true); 1457 } 1458 1459 switch (mode) { 1460 case SPECTRE_V2_NONE: 1461 case SPECTRE_V2_EIBRS: 1462 break; 1463 1464 case SPECTRE_V2_IBRS: 1465 setup_force_cpu_cap(X86_FEATURE_KERNEL_IBRS); 1466 if (boot_cpu_has(X86_FEATURE_IBRS_ENHANCED)) 1467 pr_warn(SPECTRE_V2_IBRS_PERF_MSG); 1468 break; 1469 1470 case SPECTRE_V2_LFENCE: 1471 case SPECTRE_V2_EIBRS_LFENCE: 1472 setup_force_cpu_cap(X86_FEATURE_RETPOLINE_LFENCE); 1473 fallthrough; 1474 1475 case SPECTRE_V2_RETPOLINE: 1476 case SPECTRE_V2_EIBRS_RETPOLINE: 1477 setup_force_cpu_cap(X86_FEATURE_RETPOLINE); 1478 break; 1479 } 1480 1481 /* 1482 * Disable alternate RSB predictions in kernel when indirect CALLs and 1483 * JMPs gets protection against BHI and Intramode-BTI, but RET 1484 * prediction from a non-RSB predictor is still a risk. 1485 */ 1486 if (mode == SPECTRE_V2_EIBRS_LFENCE || 1487 mode == SPECTRE_V2_EIBRS_RETPOLINE || 1488 mode == SPECTRE_V2_RETPOLINE) 1489 spec_ctrl_disable_kernel_rrsba(); 1490 1491 spectre_v2_enabled = mode; 1492 pr_info("%s\n", spectre_v2_strings[mode]); 1493 1494 /* 1495 * If Spectre v2 protection has been enabled, fill the RSB during a 1496 * context switch. In general there are two types of RSB attacks 1497 * across context switches, for which the CALLs/RETs may be unbalanced. 1498 * 1499 * 1) RSB underflow 1500 * 1501 * Some Intel parts have "bottomless RSB". When the RSB is empty, 1502 * speculated return targets may come from the branch predictor, 1503 * which could have a user-poisoned BTB or BHB entry. 1504 * 1505 * AMD has it even worse: *all* returns are speculated from the BTB, 1506 * regardless of the state of the RSB. 1507 * 1508 * When IBRS or eIBRS is enabled, the "user -> kernel" attack 1509 * scenario is mitigated by the IBRS branch prediction isolation 1510 * properties, so the RSB buffer filling wouldn't be necessary to 1511 * protect against this type of attack. 1512 * 1513 * The "user -> user" attack scenario is mitigated by RSB filling. 1514 * 1515 * 2) Poisoned RSB entry 1516 * 1517 * If the 'next' in-kernel return stack is shorter than 'prev', 1518 * 'next' could be tricked into speculating with a user-poisoned RSB 1519 * entry. 1520 * 1521 * The "user -> kernel" attack scenario is mitigated by SMEP and 1522 * eIBRS. 1523 * 1524 * The "user -> user" scenario, also known as SpectreBHB, requires 1525 * RSB clearing. 1526 * 1527 * So to mitigate all cases, unconditionally fill RSB on context 1528 * switches. 1529 * 1530 * FIXME: Is this pointless for retbleed-affected AMD? 1531 */ 1532 setup_force_cpu_cap(X86_FEATURE_RSB_CTXSW); 1533 pr_info("Spectre v2 / SpectreRSB mitigation: Filling RSB on context switch\n"); 1534 1535 spectre_v2_determine_rsb_fill_type_at_vmexit(mode); 1536 1537 /* 1538 * Retpoline protects the kernel, but doesn't protect firmware. IBRS 1539 * and Enhanced IBRS protect firmware too, so enable IBRS around 1540 * firmware calls only when IBRS / Enhanced IBRS aren't otherwise 1541 * enabled. 1542 * 1543 * Use "mode" to check Enhanced IBRS instead of boot_cpu_has(), because 1544 * the user might select retpoline on the kernel command line and if 1545 * the CPU supports Enhanced IBRS, kernel might un-intentionally not 1546 * enable IBRS around firmware calls. 1547 */ 1548 if (boot_cpu_has_bug(X86_BUG_RETBLEED) && 1549 boot_cpu_has(X86_FEATURE_IBPB) && 1550 (boot_cpu_data.x86_vendor == X86_VENDOR_AMD || 1551 boot_cpu_data.x86_vendor == X86_VENDOR_HYGON)) { 1552 1553 if (retbleed_cmd != RETBLEED_CMD_IBPB) { 1554 setup_force_cpu_cap(X86_FEATURE_USE_IBPB_FW); 1555 pr_info("Enabling Speculation Barrier for firmware calls\n"); 1556 } 1557 1558 } else if (boot_cpu_has(X86_FEATURE_IBRS) && !spectre_v2_in_ibrs_mode(mode)) { 1559 setup_force_cpu_cap(X86_FEATURE_USE_IBRS_FW); 1560 pr_info("Enabling Restricted Speculation for firmware calls\n"); 1561 } 1562 1563 /* Set up IBPB and STIBP depending on the general spectre V2 command */ 1564 spectre_v2_cmd = cmd; 1565 } 1566 1567 static void update_stibp_msr(void * __unused) 1568 { 1569 u64 val = spec_ctrl_current() | (x86_spec_ctrl_base & SPEC_CTRL_STIBP); 1570 write_spec_ctrl_current(val, true); 1571 } 1572 1573 /* Update x86_spec_ctrl_base in case SMT state changed. */ 1574 static void update_stibp_strict(void) 1575 { 1576 u64 mask = x86_spec_ctrl_base & ~SPEC_CTRL_STIBP; 1577 1578 if (sched_smt_active()) 1579 mask |= SPEC_CTRL_STIBP; 1580 1581 if (mask == x86_spec_ctrl_base) 1582 return; 1583 1584 pr_info("Update user space SMT mitigation: STIBP %s\n", 1585 mask & SPEC_CTRL_STIBP ? "always-on" : "off"); 1586 x86_spec_ctrl_base = mask; 1587 on_each_cpu(update_stibp_msr, NULL, 1); 1588 } 1589 1590 /* Update the static key controlling the evaluation of TIF_SPEC_IB */ 1591 static void update_indir_branch_cond(void) 1592 { 1593 if (sched_smt_active()) 1594 static_branch_enable(&switch_to_cond_stibp); 1595 else 1596 static_branch_disable(&switch_to_cond_stibp); 1597 } 1598 1599 #undef pr_fmt 1600 #define pr_fmt(fmt) fmt 1601 1602 /* Update the static key controlling the MDS CPU buffer clear in idle */ 1603 static void update_mds_branch_idle(void) 1604 { 1605 u64 ia32_cap = x86_read_arch_cap_msr(); 1606 1607 /* 1608 * Enable the idle clearing if SMT is active on CPUs which are 1609 * affected only by MSBDS and not any other MDS variant. 1610 * 1611 * The other variants cannot be mitigated when SMT is enabled, so 1612 * clearing the buffers on idle just to prevent the Store Buffer 1613 * repartitioning leak would be a window dressing exercise. 1614 */ 1615 if (!boot_cpu_has_bug(X86_BUG_MSBDS_ONLY)) 1616 return; 1617 1618 if (sched_smt_active()) { 1619 static_branch_enable(&mds_idle_clear); 1620 } else if (mmio_mitigation == MMIO_MITIGATION_OFF || 1621 (ia32_cap & ARCH_CAP_FBSDP_NO)) { 1622 static_branch_disable(&mds_idle_clear); 1623 } 1624 } 1625 1626 #define MDS_MSG_SMT "MDS CPU bug present and SMT on, data leak possible. See https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/mds.html for more details.\n" 1627 #define TAA_MSG_SMT "TAA CPU bug present and SMT on, data leak possible. See https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/tsx_async_abort.html for more details.\n" 1628 #define MMIO_MSG_SMT "MMIO Stale Data CPU bug present and SMT on, data leak possible. See https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/processor_mmio_stale_data.html for more details.\n" 1629 1630 void cpu_bugs_smt_update(void) 1631 { 1632 mutex_lock(&spec_ctrl_mutex); 1633 1634 if (sched_smt_active() && unprivileged_ebpf_enabled() && 1635 spectre_v2_enabled == SPECTRE_V2_EIBRS_LFENCE) 1636 pr_warn_once(SPECTRE_V2_EIBRS_LFENCE_EBPF_SMT_MSG); 1637 1638 switch (spectre_v2_user_stibp) { 1639 case SPECTRE_V2_USER_NONE: 1640 break; 1641 case SPECTRE_V2_USER_STRICT: 1642 case SPECTRE_V2_USER_STRICT_PREFERRED: 1643 update_stibp_strict(); 1644 break; 1645 case SPECTRE_V2_USER_PRCTL: 1646 case SPECTRE_V2_USER_SECCOMP: 1647 update_indir_branch_cond(); 1648 break; 1649 } 1650 1651 switch (mds_mitigation) { 1652 case MDS_MITIGATION_FULL: 1653 case MDS_MITIGATION_VMWERV: 1654 if (sched_smt_active() && !boot_cpu_has(X86_BUG_MSBDS_ONLY)) 1655 pr_warn_once(MDS_MSG_SMT); 1656 update_mds_branch_idle(); 1657 break; 1658 case MDS_MITIGATION_OFF: 1659 break; 1660 } 1661 1662 switch (taa_mitigation) { 1663 case TAA_MITIGATION_VERW: 1664 case TAA_MITIGATION_UCODE_NEEDED: 1665 if (sched_smt_active()) 1666 pr_warn_once(TAA_MSG_SMT); 1667 break; 1668 case TAA_MITIGATION_TSX_DISABLED: 1669 case TAA_MITIGATION_OFF: 1670 break; 1671 } 1672 1673 switch (mmio_mitigation) { 1674 case MMIO_MITIGATION_VERW: 1675 case MMIO_MITIGATION_UCODE_NEEDED: 1676 if (sched_smt_active()) 1677 pr_warn_once(MMIO_MSG_SMT); 1678 break; 1679 case MMIO_MITIGATION_OFF: 1680 break; 1681 } 1682 1683 mutex_unlock(&spec_ctrl_mutex); 1684 } 1685 1686 #undef pr_fmt 1687 #define pr_fmt(fmt) "Speculative Store Bypass: " fmt 1688 1689 static enum ssb_mitigation ssb_mode __ro_after_init = SPEC_STORE_BYPASS_NONE; 1690 1691 /* The kernel command line selection */ 1692 enum ssb_mitigation_cmd { 1693 SPEC_STORE_BYPASS_CMD_NONE, 1694 SPEC_STORE_BYPASS_CMD_AUTO, 1695 SPEC_STORE_BYPASS_CMD_ON, 1696 SPEC_STORE_BYPASS_CMD_PRCTL, 1697 SPEC_STORE_BYPASS_CMD_SECCOMP, 1698 }; 1699 1700 static const char * const ssb_strings[] = { 1701 [SPEC_STORE_BYPASS_NONE] = "Vulnerable", 1702 [SPEC_STORE_BYPASS_DISABLE] = "Mitigation: Speculative Store Bypass disabled", 1703 [SPEC_STORE_BYPASS_PRCTL] = "Mitigation: Speculative Store Bypass disabled via prctl", 1704 [SPEC_STORE_BYPASS_SECCOMP] = "Mitigation: Speculative Store Bypass disabled via prctl and seccomp", 1705 }; 1706 1707 static const struct { 1708 const char *option; 1709 enum ssb_mitigation_cmd cmd; 1710 } ssb_mitigation_options[] __initconst = { 1711 { "auto", SPEC_STORE_BYPASS_CMD_AUTO }, /* Platform decides */ 1712 { "on", SPEC_STORE_BYPASS_CMD_ON }, /* Disable Speculative Store Bypass */ 1713 { "off", SPEC_STORE_BYPASS_CMD_NONE }, /* Don't touch Speculative Store Bypass */ 1714 { "prctl", SPEC_STORE_BYPASS_CMD_PRCTL }, /* Disable Speculative Store Bypass via prctl */ 1715 { "seccomp", SPEC_STORE_BYPASS_CMD_SECCOMP }, /* Disable Speculative Store Bypass via prctl and seccomp */ 1716 }; 1717 1718 static enum ssb_mitigation_cmd __init ssb_parse_cmdline(void) 1719 { 1720 enum ssb_mitigation_cmd cmd = SPEC_STORE_BYPASS_CMD_AUTO; 1721 char arg[20]; 1722 int ret, i; 1723 1724 if (cmdline_find_option_bool(boot_command_line, "nospec_store_bypass_disable") || 1725 cpu_mitigations_off()) { 1726 return SPEC_STORE_BYPASS_CMD_NONE; 1727 } else { 1728 ret = cmdline_find_option(boot_command_line, "spec_store_bypass_disable", 1729 arg, sizeof(arg)); 1730 if (ret < 0) 1731 return SPEC_STORE_BYPASS_CMD_AUTO; 1732 1733 for (i = 0; i < ARRAY_SIZE(ssb_mitigation_options); i++) { 1734 if (!match_option(arg, ret, ssb_mitigation_options[i].option)) 1735 continue; 1736 1737 cmd = ssb_mitigation_options[i].cmd; 1738 break; 1739 } 1740 1741 if (i >= ARRAY_SIZE(ssb_mitigation_options)) { 1742 pr_err("unknown option (%s). Switching to AUTO select\n", arg); 1743 return SPEC_STORE_BYPASS_CMD_AUTO; 1744 } 1745 } 1746 1747 return cmd; 1748 } 1749 1750 static enum ssb_mitigation __init __ssb_select_mitigation(void) 1751 { 1752 enum ssb_mitigation mode = SPEC_STORE_BYPASS_NONE; 1753 enum ssb_mitigation_cmd cmd; 1754 1755 if (!boot_cpu_has(X86_FEATURE_SSBD)) 1756 return mode; 1757 1758 cmd = ssb_parse_cmdline(); 1759 if (!boot_cpu_has_bug(X86_BUG_SPEC_STORE_BYPASS) && 1760 (cmd == SPEC_STORE_BYPASS_CMD_NONE || 1761 cmd == SPEC_STORE_BYPASS_CMD_AUTO)) 1762 return mode; 1763 1764 switch (cmd) { 1765 case SPEC_STORE_BYPASS_CMD_SECCOMP: 1766 /* 1767 * Choose prctl+seccomp as the default mode if seccomp is 1768 * enabled. 1769 */ 1770 if (IS_ENABLED(CONFIG_SECCOMP)) 1771 mode = SPEC_STORE_BYPASS_SECCOMP; 1772 else 1773 mode = SPEC_STORE_BYPASS_PRCTL; 1774 break; 1775 case SPEC_STORE_BYPASS_CMD_ON: 1776 mode = SPEC_STORE_BYPASS_DISABLE; 1777 break; 1778 case SPEC_STORE_BYPASS_CMD_AUTO: 1779 case SPEC_STORE_BYPASS_CMD_PRCTL: 1780 mode = SPEC_STORE_BYPASS_PRCTL; 1781 break; 1782 case SPEC_STORE_BYPASS_CMD_NONE: 1783 break; 1784 } 1785 1786 /* 1787 * We have three CPU feature flags that are in play here: 1788 * - X86_BUG_SPEC_STORE_BYPASS - CPU is susceptible. 1789 * - X86_FEATURE_SSBD - CPU is able to turn off speculative store bypass 1790 * - X86_FEATURE_SPEC_STORE_BYPASS_DISABLE - engage the mitigation 1791 */ 1792 if (mode == SPEC_STORE_BYPASS_DISABLE) { 1793 setup_force_cpu_cap(X86_FEATURE_SPEC_STORE_BYPASS_DISABLE); 1794 /* 1795 * Intel uses the SPEC CTRL MSR Bit(2) for this, while AMD may 1796 * use a completely different MSR and bit dependent on family. 1797 */ 1798 if (!static_cpu_has(X86_FEATURE_SPEC_CTRL_SSBD) && 1799 !static_cpu_has(X86_FEATURE_AMD_SSBD)) { 1800 x86_amd_ssb_disable(); 1801 } else { 1802 x86_spec_ctrl_base |= SPEC_CTRL_SSBD; 1803 write_spec_ctrl_current(x86_spec_ctrl_base, true); 1804 } 1805 } 1806 1807 return mode; 1808 } 1809 1810 static void ssb_select_mitigation(void) 1811 { 1812 ssb_mode = __ssb_select_mitigation(); 1813 1814 if (boot_cpu_has_bug(X86_BUG_SPEC_STORE_BYPASS)) 1815 pr_info("%s\n", ssb_strings[ssb_mode]); 1816 } 1817 1818 #undef pr_fmt 1819 #define pr_fmt(fmt) "Speculation prctl: " fmt 1820 1821 static void task_update_spec_tif(struct task_struct *tsk) 1822 { 1823 /* Force the update of the real TIF bits */ 1824 set_tsk_thread_flag(tsk, TIF_SPEC_FORCE_UPDATE); 1825 1826 /* 1827 * Immediately update the speculation control MSRs for the current 1828 * task, but for a non-current task delay setting the CPU 1829 * mitigation until it is scheduled next. 1830 * 1831 * This can only happen for SECCOMP mitigation. For PRCTL it's 1832 * always the current task. 1833 */ 1834 if (tsk == current) 1835 speculation_ctrl_update_current(); 1836 } 1837 1838 static int l1d_flush_prctl_set(struct task_struct *task, unsigned long ctrl) 1839 { 1840 1841 if (!static_branch_unlikely(&switch_mm_cond_l1d_flush)) 1842 return -EPERM; 1843 1844 switch (ctrl) { 1845 case PR_SPEC_ENABLE: 1846 set_ti_thread_flag(&task->thread_info, TIF_SPEC_L1D_FLUSH); 1847 return 0; 1848 case PR_SPEC_DISABLE: 1849 clear_ti_thread_flag(&task->thread_info, TIF_SPEC_L1D_FLUSH); 1850 return 0; 1851 default: 1852 return -ERANGE; 1853 } 1854 } 1855 1856 static int ssb_prctl_set(struct task_struct *task, unsigned long ctrl) 1857 { 1858 if (ssb_mode != SPEC_STORE_BYPASS_PRCTL && 1859 ssb_mode != SPEC_STORE_BYPASS_SECCOMP) 1860 return -ENXIO; 1861 1862 switch (ctrl) { 1863 case PR_SPEC_ENABLE: 1864 /* If speculation is force disabled, enable is not allowed */ 1865 if (task_spec_ssb_force_disable(task)) 1866 return -EPERM; 1867 task_clear_spec_ssb_disable(task); 1868 task_clear_spec_ssb_noexec(task); 1869 task_update_spec_tif(task); 1870 break; 1871 case PR_SPEC_DISABLE: 1872 task_set_spec_ssb_disable(task); 1873 task_clear_spec_ssb_noexec(task); 1874 task_update_spec_tif(task); 1875 break; 1876 case PR_SPEC_FORCE_DISABLE: 1877 task_set_spec_ssb_disable(task); 1878 task_set_spec_ssb_force_disable(task); 1879 task_clear_spec_ssb_noexec(task); 1880 task_update_spec_tif(task); 1881 break; 1882 case PR_SPEC_DISABLE_NOEXEC: 1883 if (task_spec_ssb_force_disable(task)) 1884 return -EPERM; 1885 task_set_spec_ssb_disable(task); 1886 task_set_spec_ssb_noexec(task); 1887 task_update_spec_tif(task); 1888 break; 1889 default: 1890 return -ERANGE; 1891 } 1892 return 0; 1893 } 1894 1895 static bool is_spec_ib_user_controlled(void) 1896 { 1897 return spectre_v2_user_ibpb == SPECTRE_V2_USER_PRCTL || 1898 spectre_v2_user_ibpb == SPECTRE_V2_USER_SECCOMP || 1899 spectre_v2_user_stibp == SPECTRE_V2_USER_PRCTL || 1900 spectre_v2_user_stibp == SPECTRE_V2_USER_SECCOMP; 1901 } 1902 1903 static int ib_prctl_set(struct task_struct *task, unsigned long ctrl) 1904 { 1905 switch (ctrl) { 1906 case PR_SPEC_ENABLE: 1907 if (spectre_v2_user_ibpb == SPECTRE_V2_USER_NONE && 1908 spectre_v2_user_stibp == SPECTRE_V2_USER_NONE) 1909 return 0; 1910 1911 /* 1912 * With strict mode for both IBPB and STIBP, the instruction 1913 * code paths avoid checking this task flag and instead, 1914 * unconditionally run the instruction. However, STIBP and IBPB 1915 * are independent and either can be set to conditionally 1916 * enabled regardless of the mode of the other. 1917 * 1918 * If either is set to conditional, allow the task flag to be 1919 * updated, unless it was force-disabled by a previous prctl 1920 * call. Currently, this is possible on an AMD CPU which has the 1921 * feature X86_FEATURE_AMD_STIBP_ALWAYS_ON. In this case, if the 1922 * kernel is booted with 'spectre_v2_user=seccomp', then 1923 * spectre_v2_user_ibpb == SPECTRE_V2_USER_SECCOMP and 1924 * spectre_v2_user_stibp == SPECTRE_V2_USER_STRICT_PREFERRED. 1925 */ 1926 if (!is_spec_ib_user_controlled() || 1927 task_spec_ib_force_disable(task)) 1928 return -EPERM; 1929 1930 task_clear_spec_ib_disable(task); 1931 task_update_spec_tif(task); 1932 break; 1933 case PR_SPEC_DISABLE: 1934 case PR_SPEC_FORCE_DISABLE: 1935 /* 1936 * Indirect branch speculation is always allowed when 1937 * mitigation is force disabled. 1938 */ 1939 if (spectre_v2_user_ibpb == SPECTRE_V2_USER_NONE && 1940 spectre_v2_user_stibp == SPECTRE_V2_USER_NONE) 1941 return -EPERM; 1942 1943 if (!is_spec_ib_user_controlled()) 1944 return 0; 1945 1946 task_set_spec_ib_disable(task); 1947 if (ctrl == PR_SPEC_FORCE_DISABLE) 1948 task_set_spec_ib_force_disable(task); 1949 task_update_spec_tif(task); 1950 break; 1951 default: 1952 return -ERANGE; 1953 } 1954 return 0; 1955 } 1956 1957 int arch_prctl_spec_ctrl_set(struct task_struct *task, unsigned long which, 1958 unsigned long ctrl) 1959 { 1960 switch (which) { 1961 case PR_SPEC_STORE_BYPASS: 1962 return ssb_prctl_set(task, ctrl); 1963 case PR_SPEC_INDIRECT_BRANCH: 1964 return ib_prctl_set(task, ctrl); 1965 case PR_SPEC_L1D_FLUSH: 1966 return l1d_flush_prctl_set(task, ctrl); 1967 default: 1968 return -ENODEV; 1969 } 1970 } 1971 1972 #ifdef CONFIG_SECCOMP 1973 void arch_seccomp_spec_mitigate(struct task_struct *task) 1974 { 1975 if (ssb_mode == SPEC_STORE_BYPASS_SECCOMP) 1976 ssb_prctl_set(task, PR_SPEC_FORCE_DISABLE); 1977 if (spectre_v2_user_ibpb == SPECTRE_V2_USER_SECCOMP || 1978 spectre_v2_user_stibp == SPECTRE_V2_USER_SECCOMP) 1979 ib_prctl_set(task, PR_SPEC_FORCE_DISABLE); 1980 } 1981 #endif 1982 1983 static int l1d_flush_prctl_get(struct task_struct *task) 1984 { 1985 if (!static_branch_unlikely(&switch_mm_cond_l1d_flush)) 1986 return PR_SPEC_FORCE_DISABLE; 1987 1988 if (test_ti_thread_flag(&task->thread_info, TIF_SPEC_L1D_FLUSH)) 1989 return PR_SPEC_PRCTL | PR_SPEC_ENABLE; 1990 else 1991 return PR_SPEC_PRCTL | PR_SPEC_DISABLE; 1992 } 1993 1994 static int ssb_prctl_get(struct task_struct *task) 1995 { 1996 switch (ssb_mode) { 1997 case SPEC_STORE_BYPASS_DISABLE: 1998 return PR_SPEC_DISABLE; 1999 case SPEC_STORE_BYPASS_SECCOMP: 2000 case SPEC_STORE_BYPASS_PRCTL: 2001 if (task_spec_ssb_force_disable(task)) 2002 return PR_SPEC_PRCTL | PR_SPEC_FORCE_DISABLE; 2003 if (task_spec_ssb_noexec(task)) 2004 return PR_SPEC_PRCTL | PR_SPEC_DISABLE_NOEXEC; 2005 if (task_spec_ssb_disable(task)) 2006 return PR_SPEC_PRCTL | PR_SPEC_DISABLE; 2007 return PR_SPEC_PRCTL | PR_SPEC_ENABLE; 2008 default: 2009 if (boot_cpu_has_bug(X86_BUG_SPEC_STORE_BYPASS)) 2010 return PR_SPEC_ENABLE; 2011 return PR_SPEC_NOT_AFFECTED; 2012 } 2013 } 2014 2015 static int ib_prctl_get(struct task_struct *task) 2016 { 2017 if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V2)) 2018 return PR_SPEC_NOT_AFFECTED; 2019 2020 if (spectre_v2_user_ibpb == SPECTRE_V2_USER_NONE && 2021 spectre_v2_user_stibp == SPECTRE_V2_USER_NONE) 2022 return PR_SPEC_ENABLE; 2023 else if (is_spec_ib_user_controlled()) { 2024 if (task_spec_ib_force_disable(task)) 2025 return PR_SPEC_PRCTL | PR_SPEC_FORCE_DISABLE; 2026 if (task_spec_ib_disable(task)) 2027 return PR_SPEC_PRCTL | PR_SPEC_DISABLE; 2028 return PR_SPEC_PRCTL | PR_SPEC_ENABLE; 2029 } else if (spectre_v2_user_ibpb == SPECTRE_V2_USER_STRICT || 2030 spectre_v2_user_stibp == SPECTRE_V2_USER_STRICT || 2031 spectre_v2_user_stibp == SPECTRE_V2_USER_STRICT_PREFERRED) 2032 return PR_SPEC_DISABLE; 2033 else 2034 return PR_SPEC_NOT_AFFECTED; 2035 } 2036 2037 int arch_prctl_spec_ctrl_get(struct task_struct *task, unsigned long which) 2038 { 2039 switch (which) { 2040 case PR_SPEC_STORE_BYPASS: 2041 return ssb_prctl_get(task); 2042 case PR_SPEC_INDIRECT_BRANCH: 2043 return ib_prctl_get(task); 2044 case PR_SPEC_L1D_FLUSH: 2045 return l1d_flush_prctl_get(task); 2046 default: 2047 return -ENODEV; 2048 } 2049 } 2050 2051 void x86_spec_ctrl_setup_ap(void) 2052 { 2053 if (boot_cpu_has(X86_FEATURE_MSR_SPEC_CTRL)) 2054 write_spec_ctrl_current(x86_spec_ctrl_base, true); 2055 2056 if (ssb_mode == SPEC_STORE_BYPASS_DISABLE) 2057 x86_amd_ssb_disable(); 2058 } 2059 2060 bool itlb_multihit_kvm_mitigation; 2061 EXPORT_SYMBOL_GPL(itlb_multihit_kvm_mitigation); 2062 2063 #undef pr_fmt 2064 #define pr_fmt(fmt) "L1TF: " fmt 2065 2066 /* Default mitigation for L1TF-affected CPUs */ 2067 enum l1tf_mitigations l1tf_mitigation __ro_after_init = L1TF_MITIGATION_FLUSH; 2068 #if IS_ENABLED(CONFIG_KVM_INTEL) 2069 EXPORT_SYMBOL_GPL(l1tf_mitigation); 2070 #endif 2071 enum vmx_l1d_flush_state l1tf_vmx_mitigation = VMENTER_L1D_FLUSH_AUTO; 2072 EXPORT_SYMBOL_GPL(l1tf_vmx_mitigation); 2073 2074 /* 2075 * These CPUs all support 44bits physical address space internally in the 2076 * cache but CPUID can report a smaller number of physical address bits. 2077 * 2078 * The L1TF mitigation uses the top most address bit for the inversion of 2079 * non present PTEs. When the installed memory reaches into the top most 2080 * address bit due to memory holes, which has been observed on machines 2081 * which report 36bits physical address bits and have 32G RAM installed, 2082 * then the mitigation range check in l1tf_select_mitigation() triggers. 2083 * This is a false positive because the mitigation is still possible due to 2084 * the fact that the cache uses 44bit internally. Use the cache bits 2085 * instead of the reported physical bits and adjust them on the affected 2086 * machines to 44bit if the reported bits are less than 44. 2087 */ 2088 static void override_cache_bits(struct cpuinfo_x86 *c) 2089 { 2090 if (c->x86 != 6) 2091 return; 2092 2093 switch (c->x86_model) { 2094 case INTEL_FAM6_NEHALEM: 2095 case INTEL_FAM6_WESTMERE: 2096 case INTEL_FAM6_SANDYBRIDGE: 2097 case INTEL_FAM6_IVYBRIDGE: 2098 case INTEL_FAM6_HASWELL: 2099 case INTEL_FAM6_HASWELL_L: 2100 case INTEL_FAM6_HASWELL_G: 2101 case INTEL_FAM6_BROADWELL: 2102 case INTEL_FAM6_BROADWELL_G: 2103 case INTEL_FAM6_SKYLAKE_L: 2104 case INTEL_FAM6_SKYLAKE: 2105 case INTEL_FAM6_KABYLAKE_L: 2106 case INTEL_FAM6_KABYLAKE: 2107 if (c->x86_cache_bits < 44) 2108 c->x86_cache_bits = 44; 2109 break; 2110 } 2111 } 2112 2113 static void __init l1tf_select_mitigation(void) 2114 { 2115 u64 half_pa; 2116 2117 if (!boot_cpu_has_bug(X86_BUG_L1TF)) 2118 return; 2119 2120 if (cpu_mitigations_off()) 2121 l1tf_mitigation = L1TF_MITIGATION_OFF; 2122 else if (cpu_mitigations_auto_nosmt()) 2123 l1tf_mitigation = L1TF_MITIGATION_FLUSH_NOSMT; 2124 2125 override_cache_bits(&boot_cpu_data); 2126 2127 switch (l1tf_mitigation) { 2128 case L1TF_MITIGATION_OFF: 2129 case L1TF_MITIGATION_FLUSH_NOWARN: 2130 case L1TF_MITIGATION_FLUSH: 2131 break; 2132 case L1TF_MITIGATION_FLUSH_NOSMT: 2133 case L1TF_MITIGATION_FULL: 2134 cpu_smt_disable(false); 2135 break; 2136 case L1TF_MITIGATION_FULL_FORCE: 2137 cpu_smt_disable(true); 2138 break; 2139 } 2140 2141 #if CONFIG_PGTABLE_LEVELS == 2 2142 pr_warn("Kernel not compiled for PAE. No mitigation for L1TF\n"); 2143 return; 2144 #endif 2145 2146 half_pa = (u64)l1tf_pfn_limit() << PAGE_SHIFT; 2147 if (l1tf_mitigation != L1TF_MITIGATION_OFF && 2148 e820__mapped_any(half_pa, ULLONG_MAX - half_pa, E820_TYPE_RAM)) { 2149 pr_warn("System has more than MAX_PA/2 memory. L1TF mitigation not effective.\n"); 2150 pr_info("You may make it effective by booting the kernel with mem=%llu parameter.\n", 2151 half_pa); 2152 pr_info("However, doing so will make a part of your RAM unusable.\n"); 2153 pr_info("Reading https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/l1tf.html might help you decide.\n"); 2154 return; 2155 } 2156 2157 setup_force_cpu_cap(X86_FEATURE_L1TF_PTEINV); 2158 } 2159 2160 static int __init l1tf_cmdline(char *str) 2161 { 2162 if (!boot_cpu_has_bug(X86_BUG_L1TF)) 2163 return 0; 2164 2165 if (!str) 2166 return -EINVAL; 2167 2168 if (!strcmp(str, "off")) 2169 l1tf_mitigation = L1TF_MITIGATION_OFF; 2170 else if (!strcmp(str, "flush,nowarn")) 2171 l1tf_mitigation = L1TF_MITIGATION_FLUSH_NOWARN; 2172 else if (!strcmp(str, "flush")) 2173 l1tf_mitigation = L1TF_MITIGATION_FLUSH; 2174 else if (!strcmp(str, "flush,nosmt")) 2175 l1tf_mitigation = L1TF_MITIGATION_FLUSH_NOSMT; 2176 else if (!strcmp(str, "full")) 2177 l1tf_mitigation = L1TF_MITIGATION_FULL; 2178 else if (!strcmp(str, "full,force")) 2179 l1tf_mitigation = L1TF_MITIGATION_FULL_FORCE; 2180 2181 return 0; 2182 } 2183 early_param("l1tf", l1tf_cmdline); 2184 2185 #undef pr_fmt 2186 #define pr_fmt(fmt) fmt 2187 2188 #ifdef CONFIG_SYSFS 2189 2190 #define L1TF_DEFAULT_MSG "Mitigation: PTE Inversion" 2191 2192 #if IS_ENABLED(CONFIG_KVM_INTEL) 2193 static const char * const l1tf_vmx_states[] = { 2194 [VMENTER_L1D_FLUSH_AUTO] = "auto", 2195 [VMENTER_L1D_FLUSH_NEVER] = "vulnerable", 2196 [VMENTER_L1D_FLUSH_COND] = "conditional cache flushes", 2197 [VMENTER_L1D_FLUSH_ALWAYS] = "cache flushes", 2198 [VMENTER_L1D_FLUSH_EPT_DISABLED] = "EPT disabled", 2199 [VMENTER_L1D_FLUSH_NOT_REQUIRED] = "flush not necessary" 2200 }; 2201 2202 static ssize_t l1tf_show_state(char *buf) 2203 { 2204 if (l1tf_vmx_mitigation == VMENTER_L1D_FLUSH_AUTO) 2205 return sprintf(buf, "%s\n", L1TF_DEFAULT_MSG); 2206 2207 if (l1tf_vmx_mitigation == VMENTER_L1D_FLUSH_EPT_DISABLED || 2208 (l1tf_vmx_mitigation == VMENTER_L1D_FLUSH_NEVER && 2209 sched_smt_active())) { 2210 return sprintf(buf, "%s; VMX: %s\n", L1TF_DEFAULT_MSG, 2211 l1tf_vmx_states[l1tf_vmx_mitigation]); 2212 } 2213 2214 return sprintf(buf, "%s; VMX: %s, SMT %s\n", L1TF_DEFAULT_MSG, 2215 l1tf_vmx_states[l1tf_vmx_mitigation], 2216 sched_smt_active() ? "vulnerable" : "disabled"); 2217 } 2218 2219 static ssize_t itlb_multihit_show_state(char *buf) 2220 { 2221 if (!boot_cpu_has(X86_FEATURE_MSR_IA32_FEAT_CTL) || 2222 !boot_cpu_has(X86_FEATURE_VMX)) 2223 return sprintf(buf, "KVM: Mitigation: VMX unsupported\n"); 2224 else if (!(cr4_read_shadow() & X86_CR4_VMXE)) 2225 return sprintf(buf, "KVM: Mitigation: VMX disabled\n"); 2226 else if (itlb_multihit_kvm_mitigation) 2227 return sprintf(buf, "KVM: Mitigation: Split huge pages\n"); 2228 else 2229 return sprintf(buf, "KVM: Vulnerable\n"); 2230 } 2231 #else 2232 static ssize_t l1tf_show_state(char *buf) 2233 { 2234 return sprintf(buf, "%s\n", L1TF_DEFAULT_MSG); 2235 } 2236 2237 static ssize_t itlb_multihit_show_state(char *buf) 2238 { 2239 return sprintf(buf, "Processor vulnerable\n"); 2240 } 2241 #endif 2242 2243 static ssize_t mds_show_state(char *buf) 2244 { 2245 if (boot_cpu_has(X86_FEATURE_HYPERVISOR)) { 2246 return sprintf(buf, "%s; SMT Host state unknown\n", 2247 mds_strings[mds_mitigation]); 2248 } 2249 2250 if (boot_cpu_has(X86_BUG_MSBDS_ONLY)) { 2251 return sprintf(buf, "%s; SMT %s\n", mds_strings[mds_mitigation], 2252 (mds_mitigation == MDS_MITIGATION_OFF ? "vulnerable" : 2253 sched_smt_active() ? "mitigated" : "disabled")); 2254 } 2255 2256 return sprintf(buf, "%s; SMT %s\n", mds_strings[mds_mitigation], 2257 sched_smt_active() ? "vulnerable" : "disabled"); 2258 } 2259 2260 static ssize_t tsx_async_abort_show_state(char *buf) 2261 { 2262 if ((taa_mitigation == TAA_MITIGATION_TSX_DISABLED) || 2263 (taa_mitigation == TAA_MITIGATION_OFF)) 2264 return sprintf(buf, "%s\n", taa_strings[taa_mitigation]); 2265 2266 if (boot_cpu_has(X86_FEATURE_HYPERVISOR)) { 2267 return sprintf(buf, "%s; SMT Host state unknown\n", 2268 taa_strings[taa_mitigation]); 2269 } 2270 2271 return sprintf(buf, "%s; SMT %s\n", taa_strings[taa_mitigation], 2272 sched_smt_active() ? "vulnerable" : "disabled"); 2273 } 2274 2275 static ssize_t mmio_stale_data_show_state(char *buf) 2276 { 2277 if (mmio_mitigation == MMIO_MITIGATION_OFF) 2278 return sysfs_emit(buf, "%s\n", mmio_strings[mmio_mitigation]); 2279 2280 if (boot_cpu_has(X86_FEATURE_HYPERVISOR)) { 2281 return sysfs_emit(buf, "%s; SMT Host state unknown\n", 2282 mmio_strings[mmio_mitigation]); 2283 } 2284 2285 return sysfs_emit(buf, "%s; SMT %s\n", mmio_strings[mmio_mitigation], 2286 sched_smt_active() ? "vulnerable" : "disabled"); 2287 } 2288 2289 static char *stibp_state(void) 2290 { 2291 if (spectre_v2_in_ibrs_mode(spectre_v2_enabled)) 2292 return ""; 2293 2294 switch (spectre_v2_user_stibp) { 2295 case SPECTRE_V2_USER_NONE: 2296 return ", STIBP: disabled"; 2297 case SPECTRE_V2_USER_STRICT: 2298 return ", STIBP: forced"; 2299 case SPECTRE_V2_USER_STRICT_PREFERRED: 2300 return ", STIBP: always-on"; 2301 case SPECTRE_V2_USER_PRCTL: 2302 case SPECTRE_V2_USER_SECCOMP: 2303 if (static_key_enabled(&switch_to_cond_stibp)) 2304 return ", STIBP: conditional"; 2305 } 2306 return ""; 2307 } 2308 2309 static char *ibpb_state(void) 2310 { 2311 if (boot_cpu_has(X86_FEATURE_IBPB)) { 2312 if (static_key_enabled(&switch_mm_always_ibpb)) 2313 return ", IBPB: always-on"; 2314 if (static_key_enabled(&switch_mm_cond_ibpb)) 2315 return ", IBPB: conditional"; 2316 return ", IBPB: disabled"; 2317 } 2318 return ""; 2319 } 2320 2321 static char *pbrsb_eibrs_state(void) 2322 { 2323 if (boot_cpu_has_bug(X86_BUG_EIBRS_PBRSB)) { 2324 if (boot_cpu_has(X86_FEATURE_RSB_VMEXIT_LITE) || 2325 boot_cpu_has(X86_FEATURE_RSB_VMEXIT)) 2326 return ", PBRSB-eIBRS: SW sequence"; 2327 else 2328 return ", PBRSB-eIBRS: Vulnerable"; 2329 } else { 2330 return ", PBRSB-eIBRS: Not affected"; 2331 } 2332 } 2333 2334 static ssize_t spectre_v2_show_state(char *buf) 2335 { 2336 if (spectre_v2_enabled == SPECTRE_V2_LFENCE) 2337 return sprintf(buf, "Vulnerable: LFENCE\n"); 2338 2339 if (spectre_v2_enabled == SPECTRE_V2_EIBRS && unprivileged_ebpf_enabled()) 2340 return sprintf(buf, "Vulnerable: eIBRS with unprivileged eBPF\n"); 2341 2342 if (sched_smt_active() && unprivileged_ebpf_enabled() && 2343 spectre_v2_enabled == SPECTRE_V2_EIBRS_LFENCE) 2344 return sprintf(buf, "Vulnerable: eIBRS+LFENCE with unprivileged eBPF and SMT\n"); 2345 2346 return sprintf(buf, "%s%s%s%s%s%s%s\n", 2347 spectre_v2_strings[spectre_v2_enabled], 2348 ibpb_state(), 2349 boot_cpu_has(X86_FEATURE_USE_IBRS_FW) ? ", IBRS_FW" : "", 2350 stibp_state(), 2351 boot_cpu_has(X86_FEATURE_RSB_CTXSW) ? ", RSB filling" : "", 2352 pbrsb_eibrs_state(), 2353 spectre_v2_module_string()); 2354 } 2355 2356 static ssize_t srbds_show_state(char *buf) 2357 { 2358 return sprintf(buf, "%s\n", srbds_strings[srbds_mitigation]); 2359 } 2360 2361 static ssize_t retbleed_show_state(char *buf) 2362 { 2363 if (retbleed_mitigation == RETBLEED_MITIGATION_UNRET) { 2364 if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD && 2365 boot_cpu_data.x86_vendor != X86_VENDOR_HYGON) 2366 return sprintf(buf, "Vulnerable: untrained return thunk on non-Zen uarch\n"); 2367 2368 return sprintf(buf, "%s; SMT %s\n", 2369 retbleed_strings[retbleed_mitigation], 2370 !sched_smt_active() ? "disabled" : 2371 spectre_v2_user_stibp == SPECTRE_V2_USER_STRICT || 2372 spectre_v2_user_stibp == SPECTRE_V2_USER_STRICT_PREFERRED ? 2373 "enabled with STIBP protection" : "vulnerable"); 2374 } 2375 2376 return sprintf(buf, "%s\n", retbleed_strings[retbleed_mitigation]); 2377 } 2378 2379 static ssize_t cpu_show_common(struct device *dev, struct device_attribute *attr, 2380 char *buf, unsigned int bug) 2381 { 2382 if (!boot_cpu_has_bug(bug)) 2383 return sprintf(buf, "Not affected\n"); 2384 2385 switch (bug) { 2386 case X86_BUG_CPU_MELTDOWN: 2387 if (boot_cpu_has(X86_FEATURE_PTI)) 2388 return sprintf(buf, "Mitigation: PTI\n"); 2389 2390 if (hypervisor_is_type(X86_HYPER_XEN_PV)) 2391 return sprintf(buf, "Unknown (XEN PV detected, hypervisor mitigation required)\n"); 2392 2393 break; 2394 2395 case X86_BUG_SPECTRE_V1: 2396 return sprintf(buf, "%s\n", spectre_v1_strings[spectre_v1_mitigation]); 2397 2398 case X86_BUG_SPECTRE_V2: 2399 return spectre_v2_show_state(buf); 2400 2401 case X86_BUG_SPEC_STORE_BYPASS: 2402 return sprintf(buf, "%s\n", ssb_strings[ssb_mode]); 2403 2404 case X86_BUG_L1TF: 2405 if (boot_cpu_has(X86_FEATURE_L1TF_PTEINV)) 2406 return l1tf_show_state(buf); 2407 break; 2408 2409 case X86_BUG_MDS: 2410 return mds_show_state(buf); 2411 2412 case X86_BUG_TAA: 2413 return tsx_async_abort_show_state(buf); 2414 2415 case X86_BUG_ITLB_MULTIHIT: 2416 return itlb_multihit_show_state(buf); 2417 2418 case X86_BUG_SRBDS: 2419 return srbds_show_state(buf); 2420 2421 case X86_BUG_MMIO_STALE_DATA: 2422 return mmio_stale_data_show_state(buf); 2423 2424 case X86_BUG_RETBLEED: 2425 return retbleed_show_state(buf); 2426 2427 default: 2428 break; 2429 } 2430 2431 return sprintf(buf, "Vulnerable\n"); 2432 } 2433 2434 ssize_t cpu_show_meltdown(struct device *dev, struct device_attribute *attr, char *buf) 2435 { 2436 return cpu_show_common(dev, attr, buf, X86_BUG_CPU_MELTDOWN); 2437 } 2438 2439 ssize_t cpu_show_spectre_v1(struct device *dev, struct device_attribute *attr, char *buf) 2440 { 2441 return cpu_show_common(dev, attr, buf, X86_BUG_SPECTRE_V1); 2442 } 2443 2444 ssize_t cpu_show_spectre_v2(struct device *dev, struct device_attribute *attr, char *buf) 2445 { 2446 return cpu_show_common(dev, attr, buf, X86_BUG_SPECTRE_V2); 2447 } 2448 2449 ssize_t cpu_show_spec_store_bypass(struct device *dev, struct device_attribute *attr, char *buf) 2450 { 2451 return cpu_show_common(dev, attr, buf, X86_BUG_SPEC_STORE_BYPASS); 2452 } 2453 2454 ssize_t cpu_show_l1tf(struct device *dev, struct device_attribute *attr, char *buf) 2455 { 2456 return cpu_show_common(dev, attr, buf, X86_BUG_L1TF); 2457 } 2458 2459 ssize_t cpu_show_mds(struct device *dev, struct device_attribute *attr, char *buf) 2460 { 2461 return cpu_show_common(dev, attr, buf, X86_BUG_MDS); 2462 } 2463 2464 ssize_t cpu_show_tsx_async_abort(struct device *dev, struct device_attribute *attr, char *buf) 2465 { 2466 return cpu_show_common(dev, attr, buf, X86_BUG_TAA); 2467 } 2468 2469 ssize_t cpu_show_itlb_multihit(struct device *dev, struct device_attribute *attr, char *buf) 2470 { 2471 return cpu_show_common(dev, attr, buf, X86_BUG_ITLB_MULTIHIT); 2472 } 2473 2474 ssize_t cpu_show_srbds(struct device *dev, struct device_attribute *attr, char *buf) 2475 { 2476 return cpu_show_common(dev, attr, buf, X86_BUG_SRBDS); 2477 } 2478 2479 ssize_t cpu_show_mmio_stale_data(struct device *dev, struct device_attribute *attr, char *buf) 2480 { 2481 return cpu_show_common(dev, attr, buf, X86_BUG_MMIO_STALE_DATA); 2482 } 2483 2484 ssize_t cpu_show_retbleed(struct device *dev, struct device_attribute *attr, char *buf) 2485 { 2486 return cpu_show_common(dev, attr, buf, X86_BUG_RETBLEED); 2487 } 2488 #endif 2489