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Date: Wed, 12 Oct 2022 20:26:02 -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 4.19 03/19] 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 2ef7eec6461c..cc66983e8b6a 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -1271,10 +1271,12 @@ 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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