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- // SPDX-License-Identifier: GPL-2.0
- /*
- * This contains the io-permission bitmap code - written by obz, with changes
- * by Linus. 32/64 bits code unification by Miguel Botón.
- */
- #include <linux/capability.h>
- #include <linux/security.h>
- #include <linux/syscalls.h>
- #include <linux/bitmap.h>
- #include <linux/ioport.h>
- #include <linux/sched.h>
- #include <linux/slab.h>
- #include <asm/io_bitmap.h>
- #include <asm/desc.h>
- #include <asm/syscalls.h>
- #ifdef CONFIG_X86_IOPL_IOPERM
- static atomic64_t io_bitmap_sequence;
- void io_bitmap_share(struct task_struct *tsk)
- {
- /* Can be NULL when current->thread.iopl_emul == 3 */
- if (current->thread.io_bitmap) {
- /*
- * Take a refcount on current's bitmap. It can be used by
- * both tasks as long as none of them changes the bitmap.
- */
- refcount_inc(¤t->thread.io_bitmap->refcnt);
- tsk->thread.io_bitmap = current->thread.io_bitmap;
- }
- set_tsk_thread_flag(tsk, TIF_IO_BITMAP);
- }
- static void task_update_io_bitmap(struct task_struct *tsk)
- {
- struct thread_struct *t = &tsk->thread;
- if (t->iopl_emul == 3 || t->io_bitmap) {
- /* TSS update is handled on exit to user space */
- set_tsk_thread_flag(tsk, TIF_IO_BITMAP);
- } else {
- clear_tsk_thread_flag(tsk, TIF_IO_BITMAP);
- /* Invalidate TSS */
- preempt_disable();
- tss_update_io_bitmap();
- preempt_enable();
- }
- }
- void io_bitmap_exit(struct task_struct *tsk)
- {
- struct io_bitmap *iobm = tsk->thread.io_bitmap;
- tsk->thread.io_bitmap = NULL;
- task_update_io_bitmap(tsk);
- if (iobm && refcount_dec_and_test(&iobm->refcnt))
- kfree(iobm);
- }
- /*
- * This changes the io permissions bitmap in the current task.
- */
- long ksys_ioperm(unsigned long from, unsigned long num, int turn_on)
- {
- struct thread_struct *t = ¤t->thread;
- unsigned int i, max_long;
- struct io_bitmap *iobm;
- if ((from + num <= from) || (from + num > IO_BITMAP_BITS))
- return -EINVAL;
- if (turn_on && (!capable(CAP_SYS_RAWIO) ||
- security_locked_down(LOCKDOWN_IOPORT)))
- return -EPERM;
- /*
- * If it's the first ioperm() call in this thread's lifetime, set the
- * IO bitmap up. ioperm() is much less timing critical than clone(),
- * this is why we delay this operation until now:
- */
- iobm = t->io_bitmap;
- if (!iobm) {
- /* No point to allocate a bitmap just to clear permissions */
- if (!turn_on)
- return 0;
- iobm = kmalloc(sizeof(*iobm), GFP_KERNEL);
- if (!iobm)
- return -ENOMEM;
- memset(iobm->bitmap, 0xff, sizeof(iobm->bitmap));
- refcount_set(&iobm->refcnt, 1);
- }
- /*
- * If the bitmap is not shared, then nothing can take a refcount as
- * current can obviously not fork at the same time. If it's shared
- * duplicate it and drop the refcount on the original one.
- */
- if (refcount_read(&iobm->refcnt) > 1) {
- iobm = kmemdup(iobm, sizeof(*iobm), GFP_KERNEL);
- if (!iobm)
- return -ENOMEM;
- refcount_set(&iobm->refcnt, 1);
- io_bitmap_exit(current);
- }
- /*
- * Store the bitmap pointer (might be the same if the task already
- * head one). Must be done here so freeing the bitmap when all
- * permissions are dropped has the pointer set up.
- */
- t->io_bitmap = iobm;
- /* Mark it active for context switching and exit to user mode */
- set_thread_flag(TIF_IO_BITMAP);
- /*
- * Update the tasks bitmap. The update of the TSS bitmap happens on
- * exit to user mode. So this needs no protection.
- */
- if (turn_on)
- bitmap_clear(iobm->bitmap, from, num);
- else
- bitmap_set(iobm->bitmap, from, num);
- /*
- * Search for a (possibly new) maximum. This is simple and stupid,
- * to keep it obviously correct:
- */
- max_long = UINT_MAX;
- for (i = 0; i < IO_BITMAP_LONGS; i++) {
- if (iobm->bitmap[i] != ~0UL)
- max_long = i;
- }
- /* All permissions dropped? */
- if (max_long == UINT_MAX) {
- io_bitmap_exit(current);
- return 0;
- }
- iobm->max = (max_long + 1) * sizeof(unsigned long);
- /*
- * Update the sequence number to force a TSS update on return to
- * user mode.
- */
- iobm->sequence = atomic64_add_return(1, &io_bitmap_sequence);
- return 0;
- }
- SYSCALL_DEFINE3(ioperm, unsigned long, from, unsigned long, num, int, turn_on)
- {
- return ksys_ioperm(from, num, turn_on);
- }
- /*
- * The sys_iopl functionality depends on the level argument, which if
- * granted for the task is used to enable access to all 65536 I/O ports.
- *
- * This does not use the IOPL mechanism provided by the CPU as that would
- * also allow the user space task to use the CLI/STI instructions.
- *
- * Disabling interrupts in a user space task is dangerous as it might lock
- * up the machine and the semantics vs. syscalls and exceptions is
- * undefined.
- *
- * Setting IOPL to level 0-2 is disabling I/O permissions. Level 3
- * 3 enables them.
- *
- * IOPL is strictly per thread and inherited on fork.
- */
- SYSCALL_DEFINE1(iopl, unsigned int, level)
- {
- struct thread_struct *t = ¤t->thread;
- unsigned int old;
- if (level > 3)
- return -EINVAL;
- old = t->iopl_emul;
- /* No point in going further if nothing changes */
- if (level == old)
- return 0;
- /* Trying to gain more privileges? */
- if (level > old) {
- if (!capable(CAP_SYS_RAWIO) ||
- security_locked_down(LOCKDOWN_IOPORT))
- return -EPERM;
- }
- t->iopl_emul = level;
- task_update_io_bitmap(current);
- return 0;
- }
- #else /* CONFIG_X86_IOPL_IOPERM */
- long ksys_ioperm(unsigned long from, unsigned long num, int turn_on)
- {
- return -ENOSYS;
- }
- SYSCALL_DEFINE3(ioperm, unsigned long, from, unsigned long, num, int, turn_on)
- {
- return -ENOSYS;
- }
- SYSCALL_DEFINE1(iopl, unsigned int, level)
- {
- return -ENOSYS;
- }
- #endif
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