[06/12] perf evlist: Check 'base' pointer before checking refcnt when put a mmap

Message ID 1464636298-7709-7-git-send-email-acme@kernel.org
State New
Headers show

Commit Message

Arnaldo Carvalho de Melo May 30, 2016, 7:24 p.m.
From: Wang Nan <wangnan0@huawei.com>


evlist->mmap[i]->refcnt could be 0 if an evlist has no evsel or if all
evsels don't match the evlist during mmap. For example, when all evsels
are overwritable but the evlist itself is normal. To avoid crashing,
perf should check 'base' pointer before checking refcnt, and raise bug
only when base is not NULL.

Signed-off-by: Wang Nan <wangnan0@huawei.com>

Cc: He Kuang <hekuang@huawei.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1464183898-174512-2-git-send-email-wangnan0@huawei.com
[ Renamed 'mmap' variable, it is reserved in old distros such as Ubuntu 12.04, breaking the build ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

---
 tools/perf/util/evlist.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

-- 
2.5.5

Patch

diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index 50d7b80987c0..58ede3257c61 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -856,9 +856,11 @@  static void perf_evlist__mmap_get(struct perf_evlist *evlist, int idx)
 
 static void perf_evlist__mmap_put(struct perf_evlist *evlist, int idx)
 {
-	BUG_ON(atomic_read(&evlist->mmap[idx].refcnt) == 0);
+	struct perf_mmap *md = &evlist->mmap[idx];
+
+	BUG_ON(md->base && atomic_read(&md->refcnt) == 0);
 
-	if (atomic_dec_and_test(&evlist->mmap[idx].refcnt))
+	if (atomic_dec_and_test(&md->refcnt))
 		__perf_evlist__munmap(evlist, idx);
 }