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Message-Id: <20221024113038.239469781@linuxfoundation.org>
Date: Mon, 24 Oct 2022 13:32:35 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
stable@...r.kernel.org,
syzbot+38e6c55d4969a14c1534@...kaller.appspotmail.com,
Shigeru Yoshida <syoshida@...hat.com>,
Josef Bacik <josef@...icpanda.com>,
Jens Axboe <axboe@...nel.dk>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.10 358/390] nbd: Fix hung when signal interrupts nbd_start_device_ioctl()
From: Shigeru Yoshida <syoshida@...hat.com>
[ Upstream commit 1de7c3cf48fc41cd95adb12bd1ea9033a917798a ]
syzbot reported hung task [1]. The following program is a simplified
version of the reproducer:
int main(void)
{
int sv[2], fd;
if (socketpair(AF_UNIX, SOCK_STREAM, 0, sv) < 0)
return 1;
if ((fd = open("/dev/nbd0", 0)) < 0)
return 1;
if (ioctl(fd, NBD_SET_SIZE_BLOCKS, 0x81) < 0)
return 1;
if (ioctl(fd, NBD_SET_SOCK, sv[0]) < 0)
return 1;
if (ioctl(fd, NBD_DO_IT) < 0)
return 1;
return 0;
}
When signal interrupt nbd_start_device_ioctl() waiting the condition
atomic_read(&config->recv_threads) == 0, the task can hung because it
waits the completion of the inflight IOs.
This patch fixes the issue by clearing queue, not just shutdown, when
signal interrupt nbd_start_device_ioctl().
Link: https://syzkaller.appspot.com/bug?id=7d89a3ffacd2b83fdd39549bc4d8e0a89ef21239 [1]
Reported-by: syzbot+38e6c55d4969a14c1534@...kaller.appspotmail.com
Signed-off-by: Shigeru Yoshida <syoshida@...hat.com>
Reviewed-by: Josef Bacik <josef@...icpanda.com>
Link: https://lore.kernel.org/r/20220907163502.577561-1-syoshida@redhat.com
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
drivers/block/nbd.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 4a6b82d434ee..b0d3dadeb964 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -1342,10 +1342,12 @@ static int nbd_start_device_ioctl(struct nbd_device *nbd, struct block_device *b
mutex_unlock(&nbd->config_lock);
ret = wait_event_interruptible(config->recv_wq,
atomic_read(&config->recv_threads) == 0);
- if (ret)
+ if (ret) {
sock_shutdown(nbd);
- flush_workqueue(nbd->recv_workq);
+ nbd_clear_que(nbd);
+ }
+ flush_workqueue(nbd->recv_workq);
mutex_lock(&nbd->config_lock);
nbd_bdev_reset(bdev);
/* user requested, ignore socket errors */
--
2.35.1
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