On 1/21/20 7:48 AM, Sun Ke wrote:
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@xxxxxxxxxx> --- drivers/block/nbd.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index b4607dd96185..dd1f8c2c6169 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -1264,7 +1264,12 @@ static int nbd_start_device(struct nbd_device *nbd)args = kzalloc(sizeof(*args), GFP_KERNEL);if (!args) { - sock_shutdown(nbd); + if (i == 0) + sock_shutdown(nbd); + else { + sock_shutdown(nbd); + flush_workqueue(nbd->recv_workq); + }
Just for readability sake why don't we just flush_workqueue() unconditionally, and add a comment so we know why in the future. Thanks,
Josef
