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perf: Fix mmap() accounting hole

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Vince's fuzzer once again found holes. This time it spotted a leak in
the locked page accounting.

When an event had redirected output and its close() was the last
reference to the buffer we didn't have a vm context to undo accounting.

Change the code to destroy the buffer on the last munmap() and detach
all redirected events at that time. This provides us the right context
to undo the vm accounting.

Reported-and-tested-by: Vince Weaver <vincent.weaver@maine.edu>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20130604084421.GI8923@twins.programming.kicks-ass.net
Cc: <stable@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra
2013-06-04 10:44:21 +02:00
committed by Ingo Molnar
parent 26cb63ad11
commit 9bb5d40cd9
2 changed files with 160 additions and 73 deletions
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3
kernel/events/internal.h
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@@ -31,7 +31,8 @@ struct ring_buffer {
spinlock_t event_lock;
struct list_head event_list;
int mmap_locked;
atomic_t mmap_count;
unsigned long mmap_locked;
struct user_struct *mmap_user;
struct perf_event_mmap_page *user_page;