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authorJan Kara <jack@suse.cz>2018-05-03 18:26:26 +0200
committerJens Axboe <axboe@kernel.dk>2018-05-03 16:11:37 -0600
commitb8b784958eccbf8f51ebeee65282ca3fd59ea391 (patch)
treee2173e7ba2206c19a06c0bc3fa59430b9b33f92f /fs/fs-writeback.c
parent8bfc3b4c6f9de815de4ab73784b9419348266a65 (diff)
downloadlinux-b8b784958eccbf8f51ebeee65282ca3fd59ea391.tar.bz2
bdi: Fix oops in wb_workfn()
Syzbot has reported that it can hit a NULL pointer dereference in wb_workfn() due to wb->bdi->dev being NULL. This indicates that wb_workfn() was called for an already unregistered bdi which should not happen as wb_shutdown() called from bdi_unregister() should make sure all pending writeback works are completed before bdi is unregistered. Except that wb_workfn() itself can requeue the work with: mod_delayed_work(bdi_wq, &wb->dwork, 0); and if this happens while wb_shutdown() is waiting in: flush_delayed_work(&wb->dwork); the dwork can get executed after wb_shutdown() has finished and bdi_unregister() has cleared wb->bdi->dev. Make wb_workfn() use wakeup_wb() for requeueing the work which takes all the necessary precautions against racing with bdi unregistration. CC: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> CC: Tejun Heo <tj@kernel.org> Fixes: 839a8e8660b6777e7fe4e80af1a048aebe2b5977 Reported-by: syzbot <syzbot+9873874c735f2892e7e9@syzkaller.appspotmail.com> Reviewed-by: Dave Chinner <dchinner@redhat.com> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'fs/fs-writeback.c')
-rw-r--r--fs/fs-writeback.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 47d7c151fcba..471d863958bc 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -1961,7 +1961,7 @@ void wb_workfn(struct work_struct *work)
}
if (!list_empty(&wb->work_list))
- mod_delayed_work(bdi_wq, &wb->dwork, 0);
+ wb_wakeup(wb);
else if (wb_has_dirty_io(wb) && dirty_writeback_interval)
wb_wakeup_delayed(wb);