[PATCH] i386/x86-64: Add user_mode checks to profile_pc for oprofile

Fixes a obscure user space triggerable crash during oprofiling.

Oprofile calls profile_pc from NMIs even when user_mode(regs) is not true and
the program counter is inside the kernel lock section. This opens
a race - when a user program jumps to a kernel lock address and
a NMI happens before the illegal page fault exception is raised
and the program has a unmapped esp or ebp then the kernel could
oops. NMIs have a higher priority than exceptions so that could
happen.

Add user_mode checks to i386/x86-64 profile_pc to prevent that.

Cc: John Levon <levon@movementarian.org>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/arch/x86_64/kernel/time.c b/arch/x86_64/kernel/time.c
index b9ff75992c16..e0341c6808e5 100644
--- a/arch/x86_64/kernel/time.c
+++ b/arch/x86_64/kernel/time.c
@@ -193,7 +193,7 @@ unsigned long profile_pc(struct pt_regs *regs)
            is just accounted to the spinlock function.
            Better would be to write these functions in assembler again
            and check exactly. */
-        if (in_lock_functions(pc)) {
+        if (!user_mode(regs) && in_lock_functions(pc)) {
                 char *v = *(char **)regs->rsp;
                 if ((v >= _stext && v <= _etext) ||
                         (v >= _sinittext && v <= _einittext) ||