diff options
| author | Sasha Levin <sashal@kernel.org> | 2025-09-29 07:32:38 -0400 |
|---|---|---|
| committer | Steven Rostedt (Google) <rostedt@goodmis.org> | 2025-10-03 12:13:12 -0400 |
| commit | 61e19cd2e5c5235326a13a68df1a2f8ec4eeed7b (patch) | |
| tree | da627642ad54de37ae185e71782239eaa7fec17d | |
| parent | 2378a191f440a06e4c60fb8a50f4cb708c10ba40 (diff) | |
tracing: Fix lock imbalance in s_start() memory allocation failure path
When s_start() fails to allocate memory for set_event_iter, it returns NULL
before acquiring event_mutex. However, the corresponding s_stop() function
always tries to unlock the mutex, causing a lock imbalance warning:
WARNING: bad unlock balance detected!
6.17.0-rc7-00175-g2b2e0c04f78c #7 Not tainted
-------------------------------------
syz.0.85611/376514 is trying to release lock (event_mutex) at:
[<ffffffff8dafc7a4>] traverse.part.0.constprop.0+0x2c4/0x650 fs/seq_file.c:131
but there are no more locks to release!
The issue was introduced by commit b355247df104 ("tracing: Cache ':mod:'
events for modules not loaded yet") which added the kzalloc() allocation before
the mutex lock, creating a path where s_start() could return without locking
the mutex while s_stop() would still try to unlock it.
Fix this by unconditionally acquiring the mutex immediately after allocation,
regardless of whether the allocation succeeded.
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/20250929113238.3722055-1-sashal@kernel.org
Fixes: b355247df104 ("tracing: Cache ":mod:" events for modules not loaded yet")
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
| -rw-r--r-- | kernel/trace/trace_events.c | 3 |
1 files changed, 1 insertions, 2 deletions
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c index 9f3e9537417d..e00da4182deb 100644 --- a/kernel/trace/trace_events.c +++ b/kernel/trace/trace_events.c @@ -1629,11 +1629,10 @@ static void *s_start(struct seq_file *m, loff_t *pos) loff_t l; iter = kzalloc(sizeof(*iter), GFP_KERNEL); + mutex_lock(&event_mutex); if (!iter) return NULL; - mutex_lock(&event_mutex); - iter->type = SET_EVENT_FILE; iter->file = list_entry(&tr->events, struct trace_event_file, list); |