linux-kernel - [tip:perf/core] perf mmap: Fix accessing unmapped mmap in perf_mmap__read

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Date:   Thu, 29 Mar 2018 06:58:26 -0700
From:   tip-bot for Kan Liang <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     jolsa@...nel.org, kan.liang@...ux.intel.com, tglx@...utronix.de,
        acme@...hat.com, hpa@...or.com, linux-kernel@...r.kernel.org,
        wangnan0@...wei.com, namhyung@...nel.org, mingo@...nel.org
Subject: [tip:perf/core] perf mmap: Fix accessing unmapped mmap in
 perf_mmap__read_done()

Commit-ID:  f58385f629c87a9e210108b39c1f4950d0363ad2
Gitweb:     https://git.kernel.org/tip/f58385f629c87a9e210108b39c1f4950d0363ad2
Author:     Kan Liang <kan.liang@...ux.intel.com>
AuthorDate: Mon, 26 Mar 2018 09:42:09 -0400
Committer:  Arnaldo Carvalho de Melo <acme@...hat.com>
CommitDate: Tue, 27 Mar 2018 13:13:38 -0300

perf mmap: Fix accessing unmapped mmap in perf_mmap__read_done()

There is a segmentation fault when running 'perf trace'. For example:

  [root@...et e]# perf trace -e *chdir -o /tmp/bla perf report --ignore-vmlinux -i ../perf.data

The perf_mmap__consume() could unmap the mmap. It needs to check the
refcnt in perf_mmap__read_done().

Reported-by: Arnaldo Carvalho de Melo <acme@...hat.com>
Signed-off-by: Kan Liang <kan.liang@...ux.intel.com>
Cc: Jiri Olsa <jolsa@...nel.org>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Wang Nan <wangnan0@...wei.com>
Fixes: ee023de05f35 ("perf mmap: Introduce perf_mmap__read_done()")
Link: http://lkml.kernel.org/r/1522071729-16776-1-git-send-email-kan.liang@linux.intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/perf/util/mmap.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/tools/perf/util/mmap.c b/tools/perf/util/mmap.c
index 38ca3ffb9d61..f6cfc52ff1fe 100644
--- a/tools/perf/util/mmap.c
+++ b/tools/perf/util/mmap.c
@@ -317,5 +317,11 @@ out:
  */
 void perf_mmap__read_done(struct perf_mmap *map)
 {
+	/*
+	 * Check if event was unmapped due to a POLLHUP/POLLERR.
+	 */
+	if (!refcount_read(&map->refcnt))
+		return;
+
 	map->prev = perf_mmap__read_head(map);
 }