1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * This contains the io-permission bitmap code - written by obz, with changes 4 * by Linus. 32/64 bits code unification by Miguel Botón. 5 */ 6 7 #include <linux/sched.h> 8 #include <linux/sched/task_stack.h> 9 #include <linux/kernel.h> 10 #include <linux/capability.h> 11 #include <linux/errno.h> 12 #include <linux/types.h> 13 #include <linux/ioport.h> 14 #include <linux/security.h> 15 #include <linux/smp.h> 16 #include <linux/stddef.h> 17 #include <linux/slab.h> 18 #include <linux/thread_info.h> 19 #include <linux/syscalls.h> 20 #include <linux/bitmap.h> 21 #include <asm/syscalls.h> 22 #include <asm/desc.h> 23 24 /* 25 * this changes the io permissions bitmap in the current task. 26 */ 27 long ksys_ioperm(unsigned long from, unsigned long num, int turn_on) 28 { 29 struct thread_struct *t = ¤t->thread; 30 struct tss_struct *tss; 31 unsigned int i, max_long, bytes, bytes_updated; 32 33 if ((from + num <= from) || (from + num > IO_BITMAP_BITS)) 34 return -EINVAL; 35 if (turn_on && (!capable(CAP_SYS_RAWIO) || 36 security_locked_down(LOCKDOWN_IOPORT))) 37 return -EPERM; 38 39 /* 40 * If it's the first ioperm() call in this thread's lifetime, set the 41 * IO bitmap up. ioperm() is much less timing critical than clone(), 42 * this is why we delay this operation until now: 43 */ 44 if (!t->io_bitmap_ptr) { 45 unsigned long *bitmap = kmalloc(IO_BITMAP_BYTES, GFP_KERNEL); 46 47 if (!bitmap) 48 return -ENOMEM; 49 50 memset(bitmap, 0xff, IO_BITMAP_BYTES); 51 t->io_bitmap_ptr = bitmap; 52 set_thread_flag(TIF_IO_BITMAP); 53 54 /* 55 * Now that we have an IO bitmap, we need our TSS limit to be 56 * correct. It's fine if we are preempted after doing this: 57 * with TIF_IO_BITMAP set, context switches will keep our TSS 58 * limit correct. 59 */ 60 preempt_disable(); 61 refresh_tss_limit(); 62 preempt_enable(); 63 } 64 65 /* 66 * do it in the per-thread copy and in the TSS ... 67 * 68 * Disable preemption via get_cpu() - we must not switch away 69 * because the ->io_bitmap_max value must match the bitmap 70 * contents: 71 */ 72 tss = &per_cpu(cpu_tss_rw, get_cpu()); 73 74 if (turn_on) 75 bitmap_clear(t->io_bitmap_ptr, from, num); 76 else 77 bitmap_set(t->io_bitmap_ptr, from, num); 78 79 /* 80 * Search for a (possibly new) maximum. This is simple and stupid, 81 * to keep it obviously correct: 82 */ 83 max_long = 0; 84 for (i = 0; i < IO_BITMAP_LONGS; i++) 85 if (t->io_bitmap_ptr[i] != ~0UL) 86 max_long = i; 87 88 bytes = (max_long + 1) * sizeof(unsigned long); 89 bytes_updated = max(bytes, t->io_bitmap_max); 90 91 t->io_bitmap_max = bytes; 92 93 /* Update the TSS: */ 94 memcpy(tss->io_bitmap, t->io_bitmap_ptr, bytes_updated); 95 96 put_cpu(); 97 98 return 0; 99 } 100 101 SYSCALL_DEFINE3(ioperm, unsigned long, from, unsigned long, num, int, turn_on) 102 { 103 return ksys_ioperm(from, num, turn_on); 104 } 105 106 /* 107 * sys_iopl has to be used when you want to access the IO ports 108 * beyond the 0x3ff range: to get the full 65536 ports bitmapped 109 * you'd need 8kB of bitmaps/process, which is a bit excessive. 110 * 111 * Here we just change the flags value on the stack: we allow 112 * only the super-user to do it. This depends on the stack-layout 113 * on system-call entry - see also fork() and the signal handling 114 * code. 115 */ 116 SYSCALL_DEFINE1(iopl, unsigned int, level) 117 { 118 struct pt_regs *regs = current_pt_regs(); 119 struct thread_struct *t = ¤t->thread; 120 121 /* 122 * Careful: the IOPL bits in regs->flags are undefined under Xen PV 123 * and changing them has no effect. 124 */ 125 unsigned int old = t->iopl >> X86_EFLAGS_IOPL_BIT; 126 127 if (level > 3) 128 return -EINVAL; 129 /* Trying to gain more privileges? */ 130 if (level > old) { 131 if (!capable(CAP_SYS_RAWIO) || 132 security_locked_down(LOCKDOWN_IOPORT)) 133 return -EPERM; 134 } 135 regs->flags = (regs->flags & ~X86_EFLAGS_IOPL) | 136 (level << X86_EFLAGS_IOPL_BIT); 137 t->iopl = level << X86_EFLAGS_IOPL_BIT; 138 set_iopl_mask(t->iopl); 139 140 return 0; 141 } 142