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perf_events: Fix perf_counter_mmap() hook in mprotect()

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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>
This commit is contained in:
Pekka Enberg 2010-11-08 21:29:07 +02:00 committed by Linus Torvalds
parent 814ce25211
commit 63bfd7384b
1 changed files with 1 additions and 1 deletions
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2
mm/mprotect.c
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@ -211,6 +211,7 @@ mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev,
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, start, size_t, len,
error = mprotect_fixup(vma, &prev, nstart, tmp, newflags);
if (error)
goto out;
perf_event_mmap(vma);
nstart = tmp;
if (nstart < prev->vm_end)