linux-kernel - [PATCH AUTOSEL 5.15 09/47] nbd: Fix hung when signal interrupts nbd_start_device

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20221013002124.1894077-9-sashal@kernel.org>
Date:   Wed, 12 Oct 2022 20:20:44 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Shigeru Yoshida <syoshida@...hat.com>,
        syzbot+38e6c55d4969a14c1534@...kaller.appspotmail.com,
        Josef Bacik <josef@...icpanda.com>,
        Jens Axboe <axboe@...nel.dk>, Sasha Levin <sashal@...nel.org>,
        linux-block@...r.kernel.org, nbd@...er.debian.org
Subject: [PATCH AUTOSEL 5.15 09/47] 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 b391ca062add..ec2b5dd2ce4a 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -1351,10 +1351,12 @@ 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