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22fe5b0439
There is no point to update the TSS bitmap for tasks which use I/O bitmaps on every context switch. It's enough to update it right before exiting to user space. That reduces the context switch bitmap handling to invalidating the io bitmap base offset in the TSS when the outgoing task has TIF_IO_BITMAP set. The invaldiation is done on purpose when a task with an IO bitmap switches out to prevent any possible leakage of an activated IO bitmap. It also removes the requirement to update the tasks bitmap atomically in ioperm(). Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
126 lines
3.3 KiB
C
126 lines
3.3 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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/*
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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 = 0;
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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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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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