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x86/traps: Mark fixup_bad_iret() noinstr 

This is called from deep entry ASM in a situation where instrumentation
will cause more harm than providing useful information.

Switch from memmove() to memcpy() because memmove() can't be called
from noinstr code. 

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Andy Lutomirski <luto@kernel.org>
Link: https://lkml.kernel.org/r/20200505134903.346741553@linutronix.de
This commit is contained in:
Thomas Gleixner 2020-03-25 19:53:38 +01:00
parent 1c3e5d3f60
commit d73a332936
1 changed files with 9 additions and 7 deletions
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16
arch/x86/kernel/traps.c
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@ -578,7 +578,7 @@ struct bad_iret_stack {
struct pt_regs regs;
};
asmlinkage __visible notrace
asmlinkage __visible noinstr
struct bad_iret_stack *fixup_bad_iret(struct bad_iret_stack *s)
{
/*
@ -589,19 +589,21 @@ struct bad_iret_stack *fixup_bad_iret(struct bad_iret_stack *s)
* just below the IRET frame) and we want to pretend that the
* exception came from the IRET target.
*/
struct bad_iret_stack *new_stack =
(struct bad_iret_stack *)this_cpu_read(cpu_tss_rw.x86_tss.sp0) - 1;
struct bad_iret_stack tmp, *new_stack =
(struct bad_iret_stack *)__this_cpu_read(cpu_tss_rw.x86_tss.sp0) - 1;
/* Copy the IRET target to the new stack. */
memmove(&new_stack->regs.ip, (void *)s->regs.sp, 5*8);
/* Copy the IRET target to the temporary storage. */
memcpy(&tmp.regs.ip, (void *)s->regs.sp, 5*8);
/* Copy the remainder of the stack from the current stack. */
memmove(new_stack, s, offsetof(struct bad_iret_stack, regs.ip));
memcpy(&tmp, s, offsetof(struct bad_iret_stack, regs.ip));
/* Update the entry stack */
memcpy(new_stack, &tmp, sizeof(tmp));
BUG_ON(!user_mode(&new_stack->regs));
return new_stack;
}
NOKPROBE_SYMBOL(fixup_bad_iret);
#endif
static bool is_sysenter_singlestep(struct pt_regs *regs)