[patch 06/53] prevent kprobes from catching spurious page faults

[Greg KH]

2.6.28-stable review patch.  If anyone has any objections, please let us know.
------------------

From: Masami Hiramatsu <mhiramat@xxxxxxxxxx>

commit 9be260a646bf76fa418ee519afa10196b3164681 upstream.

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@xxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 arch/x86/mm/fault.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -601,8 +601,6 @@ void __kprobes do_page_fault(struct pt_r
 
 	si_code = SEGV_MAPERR;
 
-	if (notify_page_fault(regs))
-		return;
 	if (unlikely(kmmio_fault(regs, address)))
 		return;
 
@@ -632,6 +630,9 @@ void __kprobes do_page_fault(struct pt_r
 		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.
@@ -639,6 +640,9 @@ void __kprobes do_page_fault(struct pt_r
 		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

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