diff options
| author | Jan Kara <jack@suse.cz> | 2018-05-03 18:26:26 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-05-16 10:08:42 +0200 |
| commit | 57d641003679cf452f995b6f034b567d5d4e3be3 (patch) | |
| tree | 079496ab283bc2f3e1fd01fd9c372d64ca775a5b /fs/fs-writeback.c | |
| parent | 869f538101abb7d394a9bfdc49e0874a7a07b308 (diff) | |
bdi: Fix oops in wb_workfn()
commit b8b784958eccbf8f51ebeee65282ca3fd59ea391 upstream.
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'fs/fs-writeback.c')
| -rw-r--r-- | fs/fs-writeback.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index 3d8b35f28a9b..f3aea1b8702c 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -1942,7 +1942,7 @@ 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); |