prevent kprobes from catching spurious page faults

Prevent kprobes from catching spurious faults which will cause infinite
recursive page-fault and memory corruption by stack overflow.

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Cc: <stable@kernel.org>		[2.6.28.x]
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 2 deletions

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 90dfae511a41..c76ef1d701c9 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -603,8 +603,6 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)
 
         si_code = SEGV_MAPERR;
 
-        if (notify_page_fault(regs))
-                return;
         if (unlikely(kmmio_fault(regs, address)))
                 return;
 
@@ -634,6 +632,9 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)
                 if (spurious_fault(address, error_code))
                         return;
 
+                /* kprobes don't want to hook the spurious faults. */
+                if (notify_page_fault(regs))
+                        return;
                 /*
                  * Don't take the mm semaphore here. If we fixup a prefetch
                  * fault we could otherwise deadlock.
@@ -641,6 +642,9 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)
                 goto bad_area_nosemaphore;
         }
 
+        /* kprobes don't want to hook the spurious faults. */
+        if (notify_page_fault(regs))
+                return;
 
         /*
          * It's safe to allow irq's after cr2 has been saved and the