1 // SPDX-License-Identifier: GPL-2.0
3 * This contains the io-permission bitmap code - written by obz, with changes
4 * by Linus. 32/64 bits code unification by Miguel Botón.
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>
14 #include <asm/io_bitmap.h>
16 #include <asm/syscalls.h>
18 #ifdef CONFIG_X86_IOPL_IOPERM
20 static atomic64_t io_bitmap_sequence;
22 void io_bitmap_share(struct task_struct *tsk)
24 /* Can be NULL when current->thread.iopl_emul == 3 */
25 if (current->thread.io_bitmap) {
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.
30 refcount_inc(¤t->thread.io_bitmap->refcnt);
31 tsk->thread.io_bitmap = current->thread.io_bitmap;
33 set_tsk_thread_flag(tsk, TIF_IO_BITMAP);
36 static void task_update_io_bitmap(struct task_struct *tsk)
38 struct thread_struct *t = &tsk->thread;
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);
44 clear_tsk_thread_flag(tsk, TIF_IO_BITMAP);
47 tss_update_io_bitmap();
52 void io_bitmap_exit(struct task_struct *tsk)
54 struct io_bitmap *iobm = tsk->thread.io_bitmap;
56 tsk->thread.io_bitmap = NULL;
57 task_update_io_bitmap(tsk);
58 if (iobm && refcount_dec_and_test(&iobm->refcnt))
63 * This changes the io permissions bitmap in the current task.
65 long ksys_ioperm(unsigned long from, unsigned long num, int turn_on)
67 struct thread_struct *t = ¤t->thread;
68 unsigned int i, max_long;
69 struct io_bitmap *iobm;
71 if ((from + num <= from) || (from + num > IO_BITMAP_BITS))
73 if (turn_on && (!capable(CAP_SYS_RAWIO) ||
74 security_locked_down(LOCKDOWN_IOPORT)))
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:
84 /* No point to allocate a bitmap just to clear permissions */
87 iobm = kmalloc(sizeof(*iobm), GFP_KERNEL);
91 memset(iobm->bitmap, 0xff, sizeof(iobm->bitmap));
92 refcount_set(&iobm->refcnt, 1);
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.
100 if (refcount_read(&iobm->refcnt) > 1) {
101 iobm = kmemdup(iobm, sizeof(*iobm), GFP_KERNEL);
104 refcount_set(&iobm->refcnt, 1);
105 io_bitmap_exit(current);
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.
114 /* Mark it active for context switching and exit to user mode */
115 set_thread_flag(TIF_IO_BITMAP);
118 * Update the tasks bitmap. The update of the TSS bitmap happens on
119 * exit to user mode. So this needs no protection.
122 bitmap_clear(iobm->bitmap, from, num);
124 bitmap_set(iobm->bitmap, from, num);
127 * Search for a (possibly new) maximum. This is simple and stupid,
128 * to keep it obviously correct:
131 for (i = 0; i < IO_BITMAP_LONGS; i++) {
132 if (iobm->bitmap[i] != ~0UL)
135 /* All permissions dropped? */
136 if (max_long == UINT_MAX) {
137 io_bitmap_exit(current);
141 iobm->max = (max_long + 1) * sizeof(unsigned long);
144 * Update the sequence number to force a TSS update on return to
147 iobm->sequence = atomic64_add_return(1, &io_bitmap_sequence);
152 SYSCALL_DEFINE3(ioperm, unsigned long, from, unsigned long, num, int, turn_on)
154 return ksys_ioperm(from, num, turn_on);
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.
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.
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
168 * Setting IOPL to level 0-2 is disabling I/O permissions. Level 3
171 * IOPL is strictly per thread and inherited on fork.
173 SYSCALL_DEFINE1(iopl, unsigned int, level)
175 struct thread_struct *t = ¤t->thread;
183 /* No point in going further if nothing changes */
187 /* Trying to gain more privileges? */
189 if (!capable(CAP_SYS_RAWIO) ||
190 security_locked_down(LOCKDOWN_IOPORT))
194 t->iopl_emul = level;
195 task_update_io_bitmap(current);
200 #else /* CONFIG_X86_IOPL_IOPERM */
202 long ksys_ioperm(unsigned long from, unsigned long num, int turn_on)
206 SYSCALL_DEFINE3(ioperm, unsigned long, from, unsigned long, num, int, turn_on)
211 SYSCALL_DEFINE1(iopl, unsigned int, level)