144 lines
3.6 KiB
C
144 lines
3.6 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* This contains the io-permission bitmap code - written by obz, with changes
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* by Linus. 32/64 bits code unification by Miguel Botón.
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*/
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#include <linux/capability.h>
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#include <linux/security.h>
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#include <linux/syscalls.h>
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#include <linux/bitmap.h>
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#include <linux/ioport.h>
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#include <linux/sched.h>
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#include <linux/slab.h>
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#include <asm/io_bitmap.h>
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#include <asm/desc.h>
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static atomic64_t io_bitmap_sequence;
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void io_bitmap_exit(void)
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{
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struct io_bitmap *iobm = current->thread.io_bitmap;
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current->thread.io_bitmap = NULL;
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clear_thread_flag(TIF_IO_BITMAP);
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preempt_disable();
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tss_update_io_bitmap();
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preempt_enable();
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kfree(iobm);
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}
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/*
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* this changes the io permissions bitmap in the current task.
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*/
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long ksys_ioperm(unsigned long from, unsigned long num, int turn_on)
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{
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struct thread_struct *t = ¤t->thread;
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unsigned int i, max_long;
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struct io_bitmap *iobm;
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if ((from + num <= from) || (from + num > IO_BITMAP_BITS))
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return -EINVAL;
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if (turn_on && (!capable(CAP_SYS_RAWIO) ||
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security_locked_down(LOCKDOWN_IOPORT)))
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return -EPERM;
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/*
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* If it's the first ioperm() call in this thread's lifetime, set the
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* IO bitmap up. ioperm() is much less timing critical than clone(),
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* this is why we delay this operation until now:
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*/
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iobm = t->io_bitmap;
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if (!iobm) {
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/* No point to allocate a bitmap just to clear permissions */
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if (!turn_on)
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return 0;
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iobm = kmalloc(sizeof(*iobm), GFP_KERNEL);
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if (!iobm)
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return -ENOMEM;
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memset(iobm->bitmap, 0xff, sizeof(iobm->bitmap));
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}
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/*
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* Update the tasks bitmap. The update of the TSS bitmap happens on
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* exit to user mode. So this needs no protection.
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*/
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if (turn_on)
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bitmap_clear(iobm->bitmap, from, num);
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else
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bitmap_set(iobm->bitmap, from, num);
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/*
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* Search for a (possibly new) maximum. This is simple and stupid,
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* to keep it obviously correct:
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*/
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max_long = UINT_MAX;
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for (i = 0; i < IO_BITMAP_LONGS; i++) {
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if (iobm->bitmap[i] != ~0UL)
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max_long = i;
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}
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/* All permissions dropped? */
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if (max_long == UINT_MAX) {
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io_bitmap_exit();
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return 0;
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}
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iobm->max = (max_long + 1) * sizeof(unsigned long);
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/* Update the sequence number to force an update in switch_to() */
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iobm->sequence = atomic64_add_return(1, &io_bitmap_sequence);
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/*
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* Store the bitmap pointer (might be the same if the task already
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* head one). Set the TIF flag, just in case this is the first
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* invocation.
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*/
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t->io_bitmap = iobm;
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set_thread_flag(TIF_IO_BITMAP);
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return 0;
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}
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SYSCALL_DEFINE3(ioperm, unsigned long, from, unsigned long, num, int, turn_on)
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{
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return ksys_ioperm(from, num, turn_on);
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}
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/*
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* sys_iopl has to be used when you want to access the IO ports
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* beyond the 0x3ff range: to get the full 65536 ports bitmapped
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* you'd need 8kB of bitmaps/process, which is a bit excessive.
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*
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* Here we just change the flags value on the stack: we allow
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* only the super-user to do it. This depends on the stack-layout
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* on system-call entry - see also fork() and the signal handling
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* code.
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*/
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SYSCALL_DEFINE1(iopl, unsigned int, level)
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{
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struct pt_regs *regs = current_pt_regs();
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struct thread_struct *t = ¤t->thread;
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/*
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* Careful: the IOPL bits in regs->flags are undefined under Xen PV
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* and changing them has no effect.
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*/
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unsigned int old = t->iopl >> X86_EFLAGS_IOPL_BIT;
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if (level > 3)
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return -EINVAL;
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/* Trying to gain more privileges? */
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if (level > old) {
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if (!capable(CAP_SYS_RAWIO) ||
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security_locked_down(LOCKDOWN_IOPORT))
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return -EPERM;
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}
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regs->flags = (regs->flags & ~X86_EFLAGS_IOPL) |
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(level << X86_EFLAGS_IOPL_BIT);
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t->iopl = level << X86_EFLAGS_IOPL_BIT;
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set_iopl_mask(t->iopl);
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return 0;
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}
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