linux-kernel - [PATCH 3.16 290/306] perf: Do not double free

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Date:   Wed, 15 Feb 2017 22:41:41 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Peter Zijlstra" <peterz@...radead.org>,
        "Jiri Olsa" <jolsa@...hat.com>, oleg@...hat.com,
        "Alexander Shishkin" <alexander.shishkin@...ux.intel.com>,
        "Thomas Gleixner" <tglx@...utronix.de>, vince@...ter.net,
        "Ingo Molnar" <mingo@...nel.org>, eranian@...gle.com,
        dvyukov@...gle.com,
        "Linus Torvalds" <torvalds@...ux-foundation.org>,
        "Arnaldo Carvalho de Melo" <acme@...hat.com>, panand@...hat.com,
        sasha.levin@...cle.com
Subject: [PATCH 3.16 290/306] perf: Do not double free

3.16.40-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Peter Zijlstra <peterz@...radead.org>

commit 130056275ade730e7a79c110212c8815202773ee upstream.

In case of: err_file: fput(event_file), we'll end up calling
perf_release() which in turn will free the event.

Do not then free the event _again_.

Tested-by: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Reviewed-by: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
Cc: Jiri Olsa <jolsa@...hat.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: dvyukov@...gle.com
Cc: eranian@...gle.com
Cc: oleg@...hat.com
Cc: panand@...hat.com
Cc: sasha.levin@...cle.com
Cc: vince@...ter.net
Link: http://lkml.kernel.org/r/20160224174947.697350349@infradead.org
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 kernel/events/core.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -7603,7 +7603,12 @@ err_context:
 	perf_unpin_context(ctx);
 	put_ctx(ctx);
 err_alloc:
-	free_event(event);
+	/*
+	 * If event_file is set, the fput() above will have called ->release()
+	 * and that will take care of freeing the event.
+	 */
+	if (!event_file)
+		free_event(event);
 err_cpus:
 	put_online_cpus();
 err_task: