From: Sun Ke sunke32@huawei.com
mainline inclusion from mainline-v5.6-rc1 commit 5c0dd228b5fc30a3b732c7ae2657e0161ec7ed80 category: bugfix bugzilla: 185690 CVE: NA
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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: e9e006f5fcf2 ("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: Ye Bin yebin10@huawei.com Reviewed-by: Jason Yan yanaijie@huawei.com Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- drivers/block/nbd.c | 10 ++++++++++ 1 file changed, 10 insertions(+)
diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index 33a52be762d24..775cbb4c1bbcd 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -1306,6 +1306,16 @@ 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);