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nbd: add a flush_workqueue in nbd_start_device

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[ Upstream commit 5c0dd228b5 ]

When kzalloc fail, may cause trying to destroy the
workqueue from inside the workqueue.

If num_connections is m (2 < m), and NO.1 ~ NO.n
(1 < n < m) kzalloc are successful. The NO.(n + 1)
failed. Then, nbd_start_device will return ENOMEM
to nbd_start_device_ioctl, and nbd_start_device_ioctl
will return immediately without running flush_workqueue.
However, we still have n recv threads. If nbd_release
run first, recv threads may have to drop the last
config_refs and try to destroy the workqueue from
inside the workqueue.

To fix it, add a flush_workqueue in nbd_start_device.

Fixes: e9e006f5fc ("nbd: fix max number of supported devs")
Signed-off-by: Sun Ke <sunke32@huawei.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Sun Ke 2020-01-22 11:18:57 +08:00 • committed by Greg Kroah-Hartman
commit 7ce9e00a4a
1 changed files with 10 additions and 0 deletions
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10
drivers/block/nbd.c
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@ -1216,6 +1216,16 @@ static int nbd_start_device(struct nbd_device *nbd)
args = kzalloc(sizeof(*args), GFP_KERNEL);
if (!args) {
sock_shutdown(nbd);
/*
* If num_connections is m (2 < m),
* and NO.1 ~ NO.n(1 < n < m) kzallocs are successful.
* But NO.(n + 1) failed. We still have n recv threads.
* So, add flush_workqueue here to prevent recv threads
* dropping the last config_refs and trying to destroy
* the workqueue from inside the workqueue.
*/
if (i)
flush_workqueue(nbd->recv_workq);
return -ENOMEM;
}
sk_set_memalloc(config->socks[i]->sock->sk);