[PATCH 4.1 11/78] perf: Fix double-free of the AUX buffer

Greg Kroah-Hartman
2015-09-11T22:50:35Z

From: Ben Hutchings <ben@decadent.org.uk>

commit ee9397a6fb9bc4e52677f5e33eed4abee0f515e6 upstream.

If rb->aux_refcount is decremented to zero before rb->refcount,
__rb_free_aux() may be called twice resulting in a double free of
rb->aux_pages. Fix this by adding a check to __rb_free_aux().

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 57ffc5ca679f ("perf: Fix AUX buffer refcounting")
Link: http://lkml.kernel.org/r/1437953468.12842.17.camel@decadent.org.uk
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
kernel/events/ring_buffer.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)

--- a/kernel/events/ring_buffer.c
+++ b/kernel/events/ring_buffer.c
@@ -547,11 +547,13 @@ static void __rb_free_aux(struct ring_bu
rb->aux_priv = NULL;
}

- for (pg = 0; pg < rb->aux_nr_pages; pg++)
- rb_free_aux_page(rb, pg);
+ if (rb->aux_nr_pages) {
+ for (pg = 0; pg < rb->aux_nr_pages; pg++)
+ rb_free_aux_page(rb, pg);

- kfree(rb->aux_pages);
- rb->aux_nr_pages = 0;
+ kfree(rb->aux_pages);
+ rb->aux_nr_pages = 0;
+ }
}

void rb_free_aux(struct ring_buffer *rb)