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Subject[BUGFIX][PATCH -rc/-mm] 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>
---
This patch solves memory corruption bug which I reported last week.
http://lkml.org/lkml/2009/1/27/428
Since 2.6.28 kernel also has same bug, I think it should be applied
to 2.6.28.y too.
Thanks,

arch/x86/mm/fault.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
Index: linux-2.6/arch/x86/mm/fault.c
===================================================================
--- linux-2.6.orig/arch/x86/mm/fault.c
+++ linux-2.6/arch/x86/mm/fault.c
@@ -603,8 +603,6 @@ 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;

@@ -634,6 +632,9 @@ 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.
@@ -641,6 +642,9 @@ 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
--
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America) Inc.
Software Solutions Division

e-mail: mhiramat@redhat.com



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