Commit 4a3a485b authored by Tahsin Erdogan's avatar Tahsin Erdogan Committed by Jens Axboe
Browse files

writeback: fix memory leak in wb_queue_work() 



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: default avatarJohn Sperbeck <jsperbeck@google.com>
Signed-off-by: default avatarTahsin Erdogan <tahsin@google.com>
Reviewed-by: default avatarJan Kara <jack@suse.cz>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent 0067d4b0

fs/fs-writeback.c

+21 −14
Original line number Diff line number Diff line
@@ -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);



	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);

out_unlock:

	} 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);

	}



	/*

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