diff options
| author | Kent Overstreet <kent.overstreet@gmail.com> | 2019-09-03 21:25:45 +0800 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2019-09-03 08:08:31 -0600 |
| commit | a22a9602b88fabf10847f238ff81fde5f906fef7 (patch) | |
| tree | cdda0a4f2abcfaf8627fec61a16de34e19a2223b | |
| parent | d66c9920c0cf984cf99cab5036fd5f3a1b7fba46 (diff) | |
closures: fix a race on wakeup from closure_sync
The race was when a thread using closure_sync() notices cl->s->done == 1
before the thread calling closure_put() calls wake_up_process(). Then,
it's possible for that thread to return and exit just before
wake_up_process() is called - so we're trying to wake up a process that
no longer exists.
rcu_read_lock() is sufficient to protect against this, as there's an rcu
barrier somewhere in the process teardown path.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Acked-by: Coly Li <colyli@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
| -rw-r--r-- | drivers/md/bcache/closure.c | 10 |
1 files changed, 8 insertions, 2 deletions
diff --git a/drivers/md/bcache/closure.c b/drivers/md/bcache/closure.c index 73f5319295bc..c12cd809ab19 100644 --- a/drivers/md/bcache/closure.c +++ b/drivers/md/bcache/closure.c @@ -105,8 +105,14 @@ struct closure_syncer { static void closure_sync_fn(struct closure *cl) { - cl->s->done = 1; - wake_up_process(cl->s->task); + struct closure_syncer *s = cl->s; + struct task_struct *p; + + rcu_read_lock(); + p = READ_ONCE(s->task); + s->done = 1; + wake_up_process(p); + rcu_read_unlock(); } void __sched __closure_sync(struct closure *cl) |