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([240d:1a:c0d:9f00:4f2f:926a:23dd:8588]) by smtp.gmail.com with ESMTPSA id e22-20020aa79816000000b00537e328bc11sm12688689pfl.31.2022.09.07.09.35.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 07 Sep 2022 09:35:13 -0700 (PDT) From: Shigeru Yoshida To: josef@toxicpanda.com, axboe@kernel.dk Cc: linux-block@vger.kernel.org, nbd@other.debian.org, linux-kernel@vger.kernel.org, Shigeru Yoshida , syzbot+38e6c55d4969a14c1534@syzkaller.appspotmail.com Subject: [PATCH] nbd: Fix hung when signal interrupts nbd_start_device_ioctl() Date: Thu, 8 Sep 2022 01:35:02 +0900 Message-Id: <20220907163502.577561-1-syoshida@redhat.com> X-Mailer: git-send-email 2.37.3 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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@syzkaller.appspotmail.com Signed-off-by: Shigeru Yoshida --- 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 2a709daefbc4..2a2a1d996a57 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -1413,10 +1413,12 @@ static int nbd_start_device_ioctl(struct nbd_device *nbd) 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(nbd); /* user requested, ignore socket errors */ -- 2.37.3