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

From: Greg KH
Date: Tue Feb 10 2009 - 14:05:50 EST


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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