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    Subject[239/289] perf_events: Fix perf_counter_mmap() hook in mprotect()
    2.6.36-stable review patch.  If anyone has any objections, please let us know.

    ------------------

    From: Pekka Enberg <penberg@kernel.org>

    commit 63bfd7384b119409685a17d5c58f0b56e5dc03da upstream.

    As pointed out by Linus, commit dab5855 ("perf_counter: Add mmap event hooks to
    mprotect()") is fundamentally wrong as mprotect_fixup() can free 'vma' due to
    merging. Fix the problem by moving perf_event_mmap() hook to
    mprotect_fixup().

    Note: there's another successful return path from mprotect_fixup() if old
    flags equal to new flags. We don't, however, need to call
    perf_event_mmap() there because 'perf' already knows the VMA is
    executable.

    Reported-by: Dave Jones <davej@redhat.com>
    Analyzed-by: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Ingo Molnar <mingo@elte.hu>
    Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
    Signed-off-by: Pekka Enberg <penberg@kernel.org>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

    ---
    mm/mprotect.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    --- a/mm/mprotect.c
    +++ b/mm/mprotect.c
    @@ -211,6 +211,7 @@ success:
    mmu_notifier_invalidate_range_end(mm, start, end);
    vm_stat_account(mm, oldflags, vma->vm_file, -nrpages);
    vm_stat_account(mm, newflags, vma->vm_file, nrpages);
    + perf_event_mmap(vma);
    return 0;

    fail:
    @@ -299,7 +300,6 @@ SYSCALL_DEFINE3(mprotect, unsigned long,
    error = mprotect_fixup(vma, &prev, nstart, tmp, newflags);
    if (error)
    goto out;
    - perf_event_mmap(vma);
    nstart = tmp;

    if (nstart < prev->vm_end)



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