1 #include <linux/mm.h> 2 #include <linux/slab.h> 3 #include <linux/string.h> 4 #include <linux/compiler.h> 5 #include <linux/export.h> 6 #include <linux/err.h> 7 #include <linux/sched.h> 8 #include <linux/security.h> 9 #include <linux/swap.h> 10 #include <linux/swapops.h> 11 #include <linux/mman.h> 12 #include <linux/hugetlb.h> 13 #include <linux/vmalloc.h> 14 #include <linux/userfaultfd_k.h> 15 16 #include <asm/sections.h> 17 #include <linux/uaccess.h> 18 19 #include "internal.h" 20 21 static inline int is_kernel_rodata(unsigned long addr) 22 { 23 return addr >= (unsigned long)__start_rodata && 24 addr < (unsigned long)__end_rodata; 25 } 26 27 /** 28 * kfree_const - conditionally free memory 29 * @x: pointer to the memory 30 * 31 * Function calls kfree only if @x is not in .rodata section. 32 */ 33 void kfree_const(const void *x) 34 { 35 if (!is_kernel_rodata((unsigned long)x)) 36 kfree(x); 37 } 38 EXPORT_SYMBOL(kfree_const); 39 40 /** 41 * kstrdup - allocate space for and copy an existing string 42 * @s: the string to duplicate 43 * @gfp: the GFP mask used in the kmalloc() call when allocating memory 44 */ 45 char *kstrdup(const char *s, gfp_t gfp) 46 { 47 size_t len; 48 char *buf; 49 50 if (!s) 51 return NULL; 52 53 len = strlen(s) + 1; 54 buf = kmalloc_track_caller(len, gfp); 55 if (buf) 56 memcpy(buf, s, len); 57 return buf; 58 } 59 EXPORT_SYMBOL(kstrdup); 60 61 /** 62 * kstrdup_const - conditionally duplicate an existing const string 63 * @s: the string to duplicate 64 * @gfp: the GFP mask used in the kmalloc() call when allocating memory 65 * 66 * Function returns source string if it is in .rodata section otherwise it 67 * fallbacks to kstrdup. 68 * Strings allocated by kstrdup_const should be freed by kfree_const. 69 */ 70 const char *kstrdup_const(const char *s, gfp_t gfp) 71 { 72 if (is_kernel_rodata((unsigned long)s)) 73 return s; 74 75 return kstrdup(s, gfp); 76 } 77 EXPORT_SYMBOL(kstrdup_const); 78 79 /** 80 * kstrndup - allocate space for and copy an existing string 81 * @s: the string to duplicate 82 * @max: read at most @max chars from @s 83 * @gfp: the GFP mask used in the kmalloc() call when allocating memory 84 */ 85 char *kstrndup(const char *s, size_t max, gfp_t gfp) 86 { 87 size_t len; 88 char *buf; 89 90 if (!s) 91 return NULL; 92 93 len = strnlen(s, max); 94 buf = kmalloc_track_caller(len+1, gfp); 95 if (buf) { 96 memcpy(buf, s, len); 97 buf[len] = '\0'; 98 } 99 return buf; 100 } 101 EXPORT_SYMBOL(kstrndup); 102 103 /** 104 * kmemdup - duplicate region of memory 105 * 106 * @src: memory region to duplicate 107 * @len: memory region length 108 * @gfp: GFP mask to use 109 */ 110 void *kmemdup(const void *src, size_t len, gfp_t gfp) 111 { 112 void *p; 113 114 p = kmalloc_track_caller(len, gfp); 115 if (p) 116 memcpy(p, src, len); 117 return p; 118 } 119 EXPORT_SYMBOL(kmemdup); 120 121 /** 122 * memdup_user - duplicate memory region from user space 123 * 124 * @src: source address in user space 125 * @len: number of bytes to copy 126 * 127 * Returns an ERR_PTR() on failure. 128 */ 129 void *memdup_user(const void __user *src, size_t len) 130 { 131 void *p; 132 133 /* 134 * Always use GFP_KERNEL, since copy_from_user() can sleep and 135 * cause pagefault, which makes it pointless to use GFP_NOFS 136 * or GFP_ATOMIC. 137 */ 138 p = kmalloc_track_caller(len, GFP_KERNEL); 139 if (!p) 140 return ERR_PTR(-ENOMEM); 141 142 if (copy_from_user(p, src, len)) { 143 kfree(p); 144 return ERR_PTR(-EFAULT); 145 } 146 147 return p; 148 } 149 EXPORT_SYMBOL(memdup_user); 150 151 /* 152 * strndup_user - duplicate an existing string from user space 153 * @s: The string to duplicate 154 * @n: Maximum number of bytes to copy, including the trailing NUL. 155 */ 156 char *strndup_user(const char __user *s, long n) 157 { 158 char *p; 159 long length; 160 161 length = strnlen_user(s, n); 162 163 if (!length) 164 return ERR_PTR(-EFAULT); 165 166 if (length > n) 167 return ERR_PTR(-EINVAL); 168 169 p = memdup_user(s, length); 170 171 if (IS_ERR(p)) 172 return p; 173 174 p[length - 1] = '\0'; 175 176 return p; 177 } 178 EXPORT_SYMBOL(strndup_user); 179 180 /** 181 * memdup_user_nul - duplicate memory region from user space and NUL-terminate 182 * 183 * @src: source address in user space 184 * @len: number of bytes to copy 185 * 186 * Returns an ERR_PTR() on failure. 187 */ 188 void *memdup_user_nul(const void __user *src, size_t len) 189 { 190 char *p; 191 192 /* 193 * Always use GFP_KERNEL, since copy_from_user() can sleep and 194 * cause pagefault, which makes it pointless to use GFP_NOFS 195 * or GFP_ATOMIC. 196 */ 197 p = kmalloc_track_caller(len + 1, GFP_KERNEL); 198 if (!p) 199 return ERR_PTR(-ENOMEM); 200 201 if (copy_from_user(p, src, len)) { 202 kfree(p); 203 return ERR_PTR(-EFAULT); 204 } 205 p[len] = '\0'; 206 207 return p; 208 } 209 EXPORT_SYMBOL(memdup_user_nul); 210 211 void __vma_link_list(struct mm_struct *mm, struct vm_area_struct *vma, 212 struct vm_area_struct *prev, struct rb_node *rb_parent) 213 { 214 struct vm_area_struct *next; 215 216 vma->vm_prev = prev; 217 if (prev) { 218 next = prev->vm_next; 219 prev->vm_next = vma; 220 } else { 221 mm->mmap = vma; 222 if (rb_parent) 223 next = rb_entry(rb_parent, 224 struct vm_area_struct, vm_rb); 225 else 226 next = NULL; 227 } 228 vma->vm_next = next; 229 if (next) 230 next->vm_prev = vma; 231 } 232 233 /* Check if the vma is being used as a stack by this task */ 234 int vma_is_stack_for_current(struct vm_area_struct *vma) 235 { 236 struct task_struct * __maybe_unused t = current; 237 238 return (vma->vm_start <= KSTK_ESP(t) && vma->vm_end >= KSTK_ESP(t)); 239 } 240 241 #if defined(CONFIG_MMU) && !defined(HAVE_ARCH_PICK_MMAP_LAYOUT) 242 void arch_pick_mmap_layout(struct mm_struct *mm) 243 { 244 mm->mmap_base = TASK_UNMAPPED_BASE; 245 mm->get_unmapped_area = arch_get_unmapped_area; 246 } 247 #endif 248 249 /* 250 * Like get_user_pages_fast() except its IRQ-safe in that it won't fall 251 * back to the regular GUP. 252 * If the architecture not support this function, simply return with no 253 * page pinned 254 */ 255 int __weak __get_user_pages_fast(unsigned long start, 256 int nr_pages, int write, struct page **pages) 257 { 258 return 0; 259 } 260 EXPORT_SYMBOL_GPL(__get_user_pages_fast); 261 262 /** 263 * get_user_pages_fast() - pin user pages in memory 264 * @start: starting user address 265 * @nr_pages: number of pages from start to pin 266 * @write: whether pages will be written to 267 * @pages: array that receives pointers to the pages pinned. 268 * Should be at least nr_pages long. 269 * 270 * Returns number of pages pinned. This may be fewer than the number 271 * requested. If nr_pages is 0 or negative, returns 0. If no pages 272 * were pinned, returns -errno. 273 * 274 * get_user_pages_fast provides equivalent functionality to get_user_pages, 275 * operating on current and current->mm, with force=0 and vma=NULL. However 276 * unlike get_user_pages, it must be called without mmap_sem held. 277 * 278 * get_user_pages_fast may take mmap_sem and page table locks, so no 279 * assumptions can be made about lack of locking. get_user_pages_fast is to be 280 * implemented in a way that is advantageous (vs get_user_pages()) when the 281 * user memory area is already faulted in and present in ptes. However if the 282 * pages have to be faulted in, it may turn out to be slightly slower so 283 * callers need to carefully consider what to use. On many architectures, 284 * get_user_pages_fast simply falls back to get_user_pages. 285 */ 286 int __weak get_user_pages_fast(unsigned long start, 287 int nr_pages, int write, struct page **pages) 288 { 289 return get_user_pages_unlocked(start, nr_pages, pages, 290 write ? FOLL_WRITE : 0); 291 } 292 EXPORT_SYMBOL_GPL(get_user_pages_fast); 293 294 unsigned long vm_mmap_pgoff(struct file *file, unsigned long addr, 295 unsigned long len, unsigned long prot, 296 unsigned long flag, unsigned long pgoff) 297 { 298 unsigned long ret; 299 struct mm_struct *mm = current->mm; 300 unsigned long populate; 301 LIST_HEAD(uf); 302 303 ret = security_mmap_file(file, prot, flag); 304 if (!ret) { 305 if (down_write_killable(&mm->mmap_sem)) 306 return -EINTR; 307 ret = do_mmap_pgoff(file, addr, len, prot, flag, pgoff, 308 &populate, &uf); 309 up_write(&mm->mmap_sem); 310 userfaultfd_unmap_complete(mm, &uf); 311 if (populate) 312 mm_populate(ret, populate); 313 } 314 return ret; 315 } 316 317 unsigned long vm_mmap(struct file *file, unsigned long addr, 318 unsigned long len, unsigned long prot, 319 unsigned long flag, unsigned long offset) 320 { 321 if (unlikely(offset + PAGE_ALIGN(len) < offset)) 322 return -EINVAL; 323 if (unlikely(offset_in_page(offset))) 324 return -EINVAL; 325 326 return vm_mmap_pgoff(file, addr, len, prot, flag, offset >> PAGE_SHIFT); 327 } 328 EXPORT_SYMBOL(vm_mmap); 329 330 void kvfree(const void *addr) 331 { 332 if (is_vmalloc_addr(addr)) 333 vfree(addr); 334 else 335 kfree(addr); 336 } 337 EXPORT_SYMBOL(kvfree); 338 339 static inline void *__page_rmapping(struct page *page) 340 { 341 unsigned long mapping; 342 343 mapping = (unsigned long)page->mapping; 344 mapping &= ~PAGE_MAPPING_FLAGS; 345 346 return (void *)mapping; 347 } 348 349 /* Neutral page->mapping pointer to address_space or anon_vma or other */ 350 void *page_rmapping(struct page *page) 351 { 352 page = compound_head(page); 353 return __page_rmapping(page); 354 } 355 356 /* 357 * Return true if this page is mapped into pagetables. 358 * For compound page it returns true if any subpage of compound page is mapped. 359 */ 360 bool page_mapped(struct page *page) 361 { 362 int i; 363 364 if (likely(!PageCompound(page))) 365 return atomic_read(&page->_mapcount) >= 0; 366 page = compound_head(page); 367 if (atomic_read(compound_mapcount_ptr(page)) >= 0) 368 return true; 369 if (PageHuge(page)) 370 return false; 371 for (i = 0; i < hpage_nr_pages(page); i++) { 372 if (atomic_read(&page[i]._mapcount) >= 0) 373 return true; 374 } 375 return false; 376 } 377 EXPORT_SYMBOL(page_mapped); 378 379 struct anon_vma *page_anon_vma(struct page *page) 380 { 381 unsigned long mapping; 382 383 page = compound_head(page); 384 mapping = (unsigned long)page->mapping; 385 if ((mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON) 386 return NULL; 387 return __page_rmapping(page); 388 } 389 390 struct address_space *page_mapping(struct page *page) 391 { 392 struct address_space *mapping; 393 394 page = compound_head(page); 395 396 /* This happens if someone calls flush_dcache_page on slab page */ 397 if (unlikely(PageSlab(page))) 398 return NULL; 399 400 if (unlikely(PageSwapCache(page))) { 401 swp_entry_t entry; 402 403 entry.val = page_private(page); 404 return swap_address_space(entry); 405 } 406 407 mapping = page->mapping; 408 if ((unsigned long)mapping & PAGE_MAPPING_ANON) 409 return NULL; 410 411 return (void *)((unsigned long)mapping & ~PAGE_MAPPING_FLAGS); 412 } 413 EXPORT_SYMBOL(page_mapping); 414 415 /* Slow path of page_mapcount() for compound pages */ 416 int __page_mapcount(struct page *page) 417 { 418 int ret; 419 420 ret = atomic_read(&page->_mapcount) + 1; 421 /* 422 * For file THP page->_mapcount contains total number of mapping 423 * of the page: no need to look into compound_mapcount. 424 */ 425 if (!PageAnon(page) && !PageHuge(page)) 426 return ret; 427 page = compound_head(page); 428 ret += atomic_read(compound_mapcount_ptr(page)) + 1; 429 if (PageDoubleMap(page)) 430 ret--; 431 return ret; 432 } 433 EXPORT_SYMBOL_GPL(__page_mapcount); 434 435 int sysctl_overcommit_memory __read_mostly = OVERCOMMIT_GUESS; 436 int sysctl_overcommit_ratio __read_mostly = 50; 437 unsigned long sysctl_overcommit_kbytes __read_mostly; 438 int sysctl_max_map_count __read_mostly = DEFAULT_MAX_MAP_COUNT; 439 unsigned long sysctl_user_reserve_kbytes __read_mostly = 1UL << 17; /* 128MB */ 440 unsigned long sysctl_admin_reserve_kbytes __read_mostly = 1UL << 13; /* 8MB */ 441 442 int overcommit_ratio_handler(struct ctl_table *table, int write, 443 void __user *buffer, size_t *lenp, 444 loff_t *ppos) 445 { 446 int ret; 447 448 ret = proc_dointvec(table, write, buffer, lenp, ppos); 449 if (ret == 0 && write) 450 sysctl_overcommit_kbytes = 0; 451 return ret; 452 } 453 454 int overcommit_kbytes_handler(struct ctl_table *table, int write, 455 void __user *buffer, size_t *lenp, 456 loff_t *ppos) 457 { 458 int ret; 459 460 ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos); 461 if (ret == 0 && write) 462 sysctl_overcommit_ratio = 0; 463 return ret; 464 } 465 466 /* 467 * Committed memory limit enforced when OVERCOMMIT_NEVER policy is used 468 */ 469 unsigned long vm_commit_limit(void) 470 { 471 unsigned long allowed; 472 473 if (sysctl_overcommit_kbytes) 474 allowed = sysctl_overcommit_kbytes >> (PAGE_SHIFT - 10); 475 else 476 allowed = ((totalram_pages - hugetlb_total_pages()) 477 * sysctl_overcommit_ratio / 100); 478 allowed += total_swap_pages; 479 480 return allowed; 481 } 482 483 /* 484 * Make sure vm_committed_as in one cacheline and not cacheline shared with 485 * other variables. It can be updated by several CPUs frequently. 486 */ 487 struct percpu_counter vm_committed_as ____cacheline_aligned_in_smp; 488 489 /* 490 * The global memory commitment made in the system can be a metric 491 * that can be used to drive ballooning decisions when Linux is hosted 492 * as a guest. On Hyper-V, the host implements a policy engine for dynamically 493 * balancing memory across competing virtual machines that are hosted. 494 * Several metrics drive this policy engine including the guest reported 495 * memory commitment. 496 */ 497 unsigned long vm_memory_committed(void) 498 { 499 return percpu_counter_read_positive(&vm_committed_as); 500 } 501 EXPORT_SYMBOL_GPL(vm_memory_committed); 502 503 /* 504 * Check that a process has enough memory to allocate a new virtual 505 * mapping. 0 means there is enough memory for the allocation to 506 * succeed and -ENOMEM implies there is not. 507 * 508 * We currently support three overcommit policies, which are set via the 509 * vm.overcommit_memory sysctl. See Documentation/vm/overcommit-accounting 510 * 511 * Strict overcommit modes added 2002 Feb 26 by Alan Cox. 512 * Additional code 2002 Jul 20 by Robert Love. 513 * 514 * cap_sys_admin is 1 if the process has admin privileges, 0 otherwise. 515 * 516 * Note this is a helper function intended to be used by LSMs which 517 * wish to use this logic. 518 */ 519 int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin) 520 { 521 long free, allowed, reserve; 522 523 VM_WARN_ONCE(percpu_counter_read(&vm_committed_as) < 524 -(s64)vm_committed_as_batch * num_online_cpus(), 525 "memory commitment underflow"); 526 527 vm_acct_memory(pages); 528 529 /* 530 * Sometimes we want to use more memory than we have 531 */ 532 if (sysctl_overcommit_memory == OVERCOMMIT_ALWAYS) 533 return 0; 534 535 if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) { 536 free = global_page_state(NR_FREE_PAGES); 537 free += global_node_page_state(NR_FILE_PAGES); 538 539 /* 540 * shmem pages shouldn't be counted as free in this 541 * case, they can't be purged, only swapped out, and 542 * that won't affect the overall amount of available 543 * memory in the system. 544 */ 545 free -= global_node_page_state(NR_SHMEM); 546 547 free += get_nr_swap_pages(); 548 549 /* 550 * Any slabs which are created with the 551 * SLAB_RECLAIM_ACCOUNT flag claim to have contents 552 * which are reclaimable, under pressure. The dentry 553 * cache and most inode caches should fall into this 554 */ 555 free += global_page_state(NR_SLAB_RECLAIMABLE); 556 557 /* 558 * Leave reserved pages. The pages are not for anonymous pages. 559 */ 560 if (free <= totalreserve_pages) 561 goto error; 562 else 563 free -= totalreserve_pages; 564 565 /* 566 * Reserve some for root 567 */ 568 if (!cap_sys_admin) 569 free -= sysctl_admin_reserve_kbytes >> (PAGE_SHIFT - 10); 570 571 if (free > pages) 572 return 0; 573 574 goto error; 575 } 576 577 allowed = vm_commit_limit(); 578 /* 579 * Reserve some for root 580 */ 581 if (!cap_sys_admin) 582 allowed -= sysctl_admin_reserve_kbytes >> (PAGE_SHIFT - 10); 583 584 /* 585 * Don't let a single process grow so big a user can't recover 586 */ 587 if (mm) { 588 reserve = sysctl_user_reserve_kbytes >> (PAGE_SHIFT - 10); 589 allowed -= min_t(long, mm->total_vm / 32, reserve); 590 } 591 592 if (percpu_counter_read_positive(&vm_committed_as) < allowed) 593 return 0; 594 error: 595 vm_unacct_memory(pages); 596 597 return -ENOMEM; 598 } 599 600 /** 601 * get_cmdline() - copy the cmdline value to a buffer. 602 * @task: the task whose cmdline value to copy. 603 * @buffer: the buffer to copy to. 604 * @buflen: the length of the buffer. Larger cmdline values are truncated 605 * to this length. 606 * Returns the size of the cmdline field copied. Note that the copy does 607 * not guarantee an ending NULL byte. 608 */ 609 int get_cmdline(struct task_struct *task, char *buffer, int buflen) 610 { 611 int res = 0; 612 unsigned int len; 613 struct mm_struct *mm = get_task_mm(task); 614 unsigned long arg_start, arg_end, env_start, env_end; 615 if (!mm) 616 goto out; 617 if (!mm->arg_end) 618 goto out_mm; /* Shh! No looking before we're done */ 619 620 down_read(&mm->mmap_sem); 621 arg_start = mm->arg_start; 622 arg_end = mm->arg_end; 623 env_start = mm->env_start; 624 env_end = mm->env_end; 625 up_read(&mm->mmap_sem); 626 627 len = arg_end - arg_start; 628 629 if (len > buflen) 630 len = buflen; 631 632 res = access_process_vm(task, arg_start, buffer, len, FOLL_FORCE); 633 634 /* 635 * If the nul at the end of args has been overwritten, then 636 * assume application is using setproctitle(3). 637 */ 638 if (res > 0 && buffer[res-1] != '\0' && len < buflen) { 639 len = strnlen(buffer, res); 640 if (len < res) { 641 res = len; 642 } else { 643 len = env_end - env_start; 644 if (len > buflen - res) 645 len = buflen - res; 646 res += access_process_vm(task, env_start, 647 buffer+res, len, 648 FOLL_FORCE); 649 res = strnlen(buffer, res); 650 } 651 } 652 out_mm: 653 mmput(mm); 654 out: 655 return res; 656 } 657