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

diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 48468f61202cb9b47c277459f6321971540caca1..b2b36561a56951d5bd7624772f77af3348ab0bca 100644 (file)
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -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)