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 */
ksys_ioperm(unsigned long from,unsigned long num,int turn_on)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
SYSCALL_DEFINE3(ioperm,unsigned long,from,unsigned long,num,int,turn_on)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 */
SYSCALL_DEFINE1(iopl,unsigned int,level)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
