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writeback: fix memory leak in wb_queue_work()

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When WB_registered flag is not set, wb_queue_work() skips queuing the
work, but does not perform the necessary clean up. In particular, if
work->auto_free is true, it should free the memory.

The leak condition can be reprouced by following these steps:

   mount /dev/sdb /mnt/sdb
   /* In qemu console: device_del sdb */
   umount /dev/sdb

Above will result in a wb_queue_work() call on an unregistered wb and
thus leak memory.

Reported-by: John Sperbeck <jsperbeck@google.com>
Signed-off-by: Tahsin Erdogan <tahsin@google.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Tahsin Erdogan 2017-03-10 12:09:49 -08:00 committed by Jens Axboe
parent 0067d4b020
commit 4a3a485b1e
1 changed files with 21 additions and 14 deletions
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35
fs/fs-writeback.c
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@ -173,19 +173,33 @@ static void wb_wakeup(struct bdi_writeback *wb)
spin_unlock_bh(&wb->work_lock);
}
static void finish_writeback_work(struct bdi_writeback *wb,
struct wb_writeback_work *work)
{
struct wb_completion *done = work->done;
if (work->auto_free)
kfree(work);
if (done && atomic_dec_and_test(&done->cnt))
wake_up_all(&wb->bdi->wb_waitq);
}
static void wb_queue_work(struct bdi_writeback *wb,
struct wb_writeback_work *work)
{
trace_writeback_queue(wb, work);
spin_lock_bh(&wb->work_lock);
if (!test_bit(WB_registered, &wb->state))
goto out_unlock;
if (work->done)
atomic_inc(&work->done->cnt);
list_add_tail(&work->list, &wb->work_list);
mod_delayed_work(bdi_wq, &wb->dwork, 0);
out_unlock:
spin_lock_bh(&wb->work_lock);
if (test_bit(WB_registered, &wb->state)) {
list_add_tail(&work->list, &wb->work_list);
mod_delayed_work(bdi_wq, &wb->dwork, 0);
} else
finish_writeback_work(wb, work);
spin_unlock_bh(&wb->work_lock);
}
@ -1873,16 +1887,9 @@ static long wb_do_writeback(struct bdi_writeback *wb)
set_bit(WB_writeback_running, &wb->state);
while ((work = get_next_work_item(wb)) != NULL) {
struct wb_completion *done = work->done;
trace_writeback_exec(wb, work);
wrote += wb_writeback(wb, work);
if (work->auto_free)
kfree(work);
if (done && atomic_dec_and_test(&done->cnt))
wake_up_all(&wb->bdi->wb_waitq);
finish_writeback_work(wb, work);
}
/*