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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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