[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/i386/kernel/time.c b/arch/i386/kernel/time.c
index 8705c0f05788..edd00f6cee37 100644
--- a/arch/i386/kernel/time.c
+++ b/arch/i386/kernel/time.c
@@ -135,7 +135,7 @@ unsigned long profile_pc(struct pt_regs *regs)
 {
         unsigned long pc = instruction_pointer(regs);
 
-        if (in_lock_functions(pc))
+        if (!user_mode_vm(regs) && in_lock_functions(pc))
                 return *(unsigned long *)(regs->ebp + 4);
 
         return pc;