[34-longterm 095/209] perf_events: Fix perf_counter_mmap() hook in mprotect()

From: Paul Gortmaker
Date: Thu Apr 14 2011 - 13:50:51 EST

From: Pekka Enberg <penberg@xxxxxxxxxx>

| This is a commit scheduled for the next v2.6.34 longterm release. |
| If you see a problem with using this for longterm, please comment.|

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

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

Reported-by: Dave Jones <davej@xxxxxxxxxx>
Analyzed-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Reviewed-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Signed-off-by: Pekka Enberg <penberg@xxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>
mm/mprotect.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/mm/mprotect.c b/mm/mprotect.c
index 2d1bf7c..4c51338 100644
--- 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;

@@ -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)

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