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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#include <linux/capability.h>
7#include <linux/security.h>
8#include <linux/syscalls.h>
9#include <linux/bitmap.h>
10#include <linux/ioport.h>
11#include <linux/sched.h>
12#include <linux/slab.h>
13
14#include <asm/io_bitmap.h>
15#include <asm/desc.h>
16#include <asm/syscalls.h>
17
18#ifdef CONFIG_X86_IOPL_IOPERM
19
20static atomic64_t io_bitmap_sequence;
21
22void io_bitmap_share(struct task_struct *tsk)
23{
24 /* Can be NULL when current->thread.iopl_emul == 3 */
25 if (current->thread.io_bitmap) {
26 /*
27 * Take a refcount on current's bitmap. It can be used by
28 * both tasks as long as none of them changes the bitmap.
29 */
30 refcount_inc(¤t->thread.io_bitmap->refcnt);
31 tsk->thread.io_bitmap = current->thread.io_bitmap;
32 }
33 set_tsk_thread_flag(tsk, TIF_IO_BITMAP);
34}
35
36static void task_update_io_bitmap(struct task_struct *tsk)
37{
38 struct thread_struct *t = &tsk->thread;
39
40 if (t->iopl_emul == 3 || t->io_bitmap) {
41 /* TSS update is handled on exit to user space */
42 set_tsk_thread_flag(tsk, TIF_IO_BITMAP);
43 } else {
44 clear_tsk_thread_flag(tsk, TIF_IO_BITMAP);
45 /* Invalidate TSS */
46 preempt_disable();
47 tss_update_io_bitmap();
48 preempt_enable();
49 }
50}
51
52void io_bitmap_exit(struct task_struct *tsk)
53{
54 struct io_bitmap *iobm = tsk->thread.io_bitmap;
55
56 tsk->thread.io_bitmap = NULL;
57 task_update_io_bitmap(tsk);
58 if (iobm && refcount_dec_and_test(&iobm->refcnt))
59 kfree(iobm);
60}
61
62/*
63 * This changes the io permissions bitmap in the current task.
64 */
65long ksys_ioperm(unsigned long from, unsigned long num, int turn_on)
66{
67 struct thread_struct *t = ¤t->thread;
68 unsigned int i, max_long;
69 struct io_bitmap *iobm;
70
71 if ((from + num <= from) || (from + num > IO_BITMAP_BITS))
72 return -EINVAL;
73 if (turn_on && (!capable(CAP_SYS_RAWIO) ||
74 security_locked_down(LOCKDOWN_IOPORT)))
75 return -EPERM;
76
77 /*
78 * If it's the first ioperm() call in this thread's lifetime, set the
79 * IO bitmap up. ioperm() is much less timing critical than clone(),
80 * this is why we delay this operation until now:
81 */
82 iobm = t->io_bitmap;
83 if (!iobm) {
84 /* No point to allocate a bitmap just to clear permissions */
85 if (!turn_on)
86 return 0;
87 iobm = kmalloc(sizeof(*iobm), GFP_KERNEL);
88 if (!iobm)
89 return -ENOMEM;
90
91 memset(iobm->bitmap, 0xff, sizeof(iobm->bitmap));
92 refcount_set(&iobm->refcnt, 1);
93 }
94
95 /*
96 * If the bitmap is not shared, then nothing can take a refcount as
97 * current can obviously not fork at the same time. If it's shared
98 * duplicate it and drop the refcount on the original one.
99 */
100 if (refcount_read(&iobm->refcnt) > 1) {
101 iobm = kmemdup(iobm, sizeof(*iobm), GFP_KERNEL);
102 if (!iobm)
103 return -ENOMEM;
104 refcount_set(&iobm->refcnt, 1);
105 io_bitmap_exit(current);
106 }
107
108 /*
109 * Store the bitmap pointer (might be the same if the task already
110 * head one). Must be done here so freeing the bitmap when all
111 * permissions are dropped has the pointer set up.
112 */
113 t->io_bitmap = iobm;
114 /* Mark it active for context switching and exit to user mode */
115 set_thread_flag(TIF_IO_BITMAP);
116
117 /*
118 * Update the tasks bitmap. The update of the TSS bitmap happens on
119 * exit to user mode. So this needs no protection.
120 */
121 if (turn_on)
122 bitmap_clear(iobm->bitmap, from, num);
123 else
124 bitmap_set(iobm->bitmap, from, num);
125
126 /*
127 * Search for a (possibly new) maximum. This is simple and stupid,
128 * to keep it obviously correct:
129 */
130 max_long = UINT_MAX;
131 for (i = 0; i < IO_BITMAP_LONGS; i++) {
132 if (iobm->bitmap[i] != ~0UL)
133 max_long = i;
134 }
135 /* All permissions dropped? */
136 if (max_long == UINT_MAX) {
137 io_bitmap_exit(current);
138 return 0;
139 }
140
141 iobm->max = (max_long + 1) * sizeof(unsigned long);
142
143 /*
144 * Update the sequence number to force a TSS update on return to
145 * user mode.
146 */
147 iobm->sequence = atomic64_add_return(1, &io_bitmap_sequence);
148
149 return 0;
150}
151
152SYSCALL_DEFINE3(ioperm, unsigned long, from, unsigned long, num, int, turn_on)
153{
154 return ksys_ioperm(from, num, turn_on);
155}
156
157/*
158 * The sys_iopl functionality depends on the level argument, which if
159 * granted for the task is used to enable access to all 65536 I/O ports.
160 *
161 * This does not use the IOPL mechanism provided by the CPU as that would
162 * also allow the user space task to use the CLI/STI instructions.
163 *
164 * Disabling interrupts in a user space task is dangerous as it might lock
165 * up the machine and the semantics vs. syscalls and exceptions is
166 * undefined.
167 *
168 * Setting IOPL to level 0-2 is disabling I/O permissions. Level 3
169 * 3 enables them.
170 *
171 * IOPL is strictly per thread and inherited on fork.
172 */
173SYSCALL_DEFINE1(iopl, unsigned int, level)
174{
175 struct thread_struct *t = ¤t->thread;
176 unsigned int old;
177
178 if (level > 3)
179 return -EINVAL;
180
181 old = t->iopl_emul;
182
183 /* No point in going further if nothing changes */
184 if (level == old)
185 return 0;
186
187 /* Trying to gain more privileges? */
188 if (level > old) {
189 if (!capable(CAP_SYS_RAWIO) ||
190 security_locked_down(LOCKDOWN_IOPORT))
191 return -EPERM;
192 }
193
194 t->iopl_emul = level;
195 task_update_io_bitmap(current);
196
197 return 0;
198}
199
200#else /* CONFIG_X86_IOPL_IOPERM */
201
202long ksys_ioperm(unsigned long from, unsigned long num, int turn_on)
203{
204 return -ENOSYS;
205}
206SYSCALL_DEFINE3(ioperm, unsigned long, from, unsigned long, num, int, turn_on)
207{
208 return -ENOSYS;
209}
210
211SYSCALL_DEFINE1(iopl, unsigned int, level)
212{
213 return -ENOSYS;
214}
215#endif
1/*
2 * This contains the io-permission bitmap code - written by obz, with changes
3 * by Linus. 32/64 bits code unification by Miguel Botón.
4 */
5
6#include <linux/sched.h>
7#include <linux/kernel.h>
8#include <linux/capability.h>
9#include <linux/errno.h>
10#include <linux/types.h>
11#include <linux/ioport.h>
12#include <linux/smp.h>
13#include <linux/stddef.h>
14#include <linux/slab.h>
15#include <linux/thread_info.h>
16#include <linux/syscalls.h>
17#include <linux/bitmap.h>
18#include <asm/syscalls.h>
19
20/*
21 * this changes the io permissions bitmap in the current task.
22 */
23asmlinkage long sys_ioperm(unsigned long from, unsigned long num, int turn_on)
24{
25 struct thread_struct *t = ¤t->thread;
26 struct tss_struct *tss;
27 unsigned int i, max_long, bytes, bytes_updated;
28
29 if ((from + num <= from) || (from + num > IO_BITMAP_BITS))
30 return -EINVAL;
31 if (turn_on && !capable(CAP_SYS_RAWIO))
32 return -EPERM;
33
34 /*
35 * If it's the first ioperm() call in this thread's lifetime, set the
36 * IO bitmap up. ioperm() is much less timing critical than clone(),
37 * this is why we delay this operation until now:
38 */
39 if (!t->io_bitmap_ptr) {
40 unsigned long *bitmap = kmalloc(IO_BITMAP_BYTES, GFP_KERNEL);
41
42 if (!bitmap)
43 return -ENOMEM;
44
45 memset(bitmap, 0xff, IO_BITMAP_BYTES);
46 t->io_bitmap_ptr = bitmap;
47 set_thread_flag(TIF_IO_BITMAP);
48 }
49
50 /*
51 * do it in the per-thread copy and in the TSS ...
52 *
53 * Disable preemption via get_cpu() - we must not switch away
54 * because the ->io_bitmap_max value must match the bitmap
55 * contents:
56 */
57 tss = &per_cpu(cpu_tss, get_cpu());
58
59 if (turn_on)
60 bitmap_clear(t->io_bitmap_ptr, from, num);
61 else
62 bitmap_set(t->io_bitmap_ptr, from, num);
63
64 /*
65 * Search for a (possibly new) maximum. This is simple and stupid,
66 * to keep it obviously correct:
67 */
68 max_long = 0;
69 for (i = 0; i < IO_BITMAP_LONGS; i++)
70 if (t->io_bitmap_ptr[i] != ~0UL)
71 max_long = i;
72
73 bytes = (max_long + 1) * sizeof(unsigned long);
74 bytes_updated = max(bytes, t->io_bitmap_max);
75
76 t->io_bitmap_max = bytes;
77
78 /* Update the TSS: */
79 memcpy(tss->io_bitmap, t->io_bitmap_ptr, bytes_updated);
80
81 put_cpu();
82
83 return 0;
84}
85
86/*
87 * sys_iopl has to be used when you want to access the IO ports
88 * beyond the 0x3ff range: to get the full 65536 ports bitmapped
89 * you'd need 8kB of bitmaps/process, which is a bit excessive.
90 *
91 * Here we just change the flags value on the stack: we allow
92 * only the super-user to do it. This depends on the stack-layout
93 * on system-call entry - see also fork() and the signal handling
94 * code.
95 */
96SYSCALL_DEFINE1(iopl, unsigned int, level)
97{
98 struct pt_regs *regs = current_pt_regs();
99 struct thread_struct *t = ¤t->thread;
100
101 /*
102 * Careful: the IOPL bits in regs->flags are undefined under Xen PV
103 * and changing them has no effect.
104 */
105 unsigned int old = t->iopl >> X86_EFLAGS_IOPL_BIT;
106
107 if (level > 3)
108 return -EINVAL;
109 /* Trying to gain more privileges? */
110 if (level > old) {
111 if (!capable(CAP_SYS_RAWIO))
112 return -EPERM;
113 }
114 regs->flags = (regs->flags & ~X86_EFLAGS_IOPL) |
115 (level << X86_EFLAGS_IOPL_BIT);
116 t->iopl = level << X86_EFLAGS_IOPL_BIT;
117 set_iopl_mask(t->iopl);
118
119 return 0;
120}