This is a note to let you know that I've just added the patch titled

writeback: fix memory leak in wb_queue_work()

to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: writeback-fix-memory-leak-in-wb_queue_work.patch and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From foo@baz Mon Dec 18 14:12:34 CET 2017

From: Tahsin Erdogan tahsin@google.com Date: Fri, 10 Mar 2017 12:09:49 -0800 Subject: writeback: fix memory leak in wb_queue_work()

From: Tahsin Erdogan tahsin@google.com

[ Upstream commit 4a3a485b1ed0e109718cc8c9d094fa0f552de9b2 ]

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 Signed-off-by: Sasha Levin alexander.levin@verizon.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/fs-writeback.c | 35 +++++++++++++++++++++-------------- 1 file changed, 21 insertions(+), 14 deletions(-)

--- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -173,19 +173,33 @@ static void wb_wakeup(struct bdi_writeba 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); }

@@ -1875,16 +1889,9 @@ static long wb_do_writeback(struct bdi_w

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); }

/*

Patches currently in stable-queue which might be from tahsin@google.com are

queue-4.9/writeback-fix-memory-leak-in-wb_queue_work.patch