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| author | Kent Overstreet <kent.overstreet@gmail.com> | 2019-09-03 21:25:45 +0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-10-05 15:12:02 +0200 |
| commit | eb35e355da6868522d4b0c17c2cba6e4c3b6f7c6 (patch) | |
| tree | 8986e7b11c5a4ee935654053d5d435ed800e0f95 /drivers | |
| parent | 7f8a4608585def33ece1c5ad3952f93ca6348717 (diff) | |
| download | linux-stable-eb35e355da6868522d4b0c17c2cba6e4c3b6f7c6.tar.gz linux-stable-eb35e355da6868522d4b0c17c2cba6e4c3b6f7c6.tar.bz2 linux-stable-eb35e355da6868522d4b0c17c2cba6e4c3b6f7c6.zip | |
closures: fix a race on wakeup from closure_sync
[ Upstream commit a22a9602b88fabf10847f238ff81fde5f906fef7 ]
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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'drivers')
| -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) |