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From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: Sun Ke <sunke32@huawei.com>, Jens Axboe <axboe@kernel.dk>,
	Sasha Levin <sashal@kernel.org>,
	linux-block@vger.kernel.org, nbd@other.debian.org
Subject: [PATCH AUTOSEL 5.4 105/459] nbd: add a flush_workqueue in nbd_start_device
Date: Fri, 14 Feb 2020 10:55:55 -0500
Message-ID: <20200214160149.11681-105-sashal@kernel.org> (raw)
In-Reply-To: <20200214160149.11681-1-sashal@kernel.org>

From: Sun Ke <sunke32@huawei.com>

[ Upstream commit 5c0dd228b5fc30a3b732c7ae2657e0161ec7ed80 ]

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: Sasha Levin <sashal@kernel.org>
---
 drivers/block/nbd.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index b4607dd961852..78181908f0df6 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -1265,6 +1265,16 @@ 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);
-- 
2.20.1


       reply index

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20200214160149.11681-1-sashal@kernel.org>
2020-02-14 15:55 ` Sasha Levin [this message]
2020-02-14 15:55 ` [PATCH AUTOSEL 5.4 108/459] drivers/block/zram/zram_drv.c: fix error return codes not being returned in writeback_store Sasha Levin
2020-02-14 15:55 ` [PATCH AUTOSEL 5.4 109/459] block, bfq: do not plug I/O for bfq_queues with no proc refs Sasha Levin
2020-02-14 16:01 ` [PATCH AUTOSEL 5.4 420/459] rbd: work around -Wuninitialized warning Sasha Levin
2020-02-14 16:01 ` [PATCH AUTOSEL 5.4 448/459] brd: check and limit max_part par Sasha Levin

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