[PATCH openEuler-5.10 1/7] nbd: don't handle response without a corresponding request message
From: Yu Kuai <yukuai3@huawei.com> mainline inclusion from mainline-next-20211018 commit b5644a3a79bf3be5f1238db1b2f241374b27b0f0 category: bugfix bugzilla: 49890 https://gitee.com/openeuler/kernel/issues/I4DDEL Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... --------------------------- While handling a response message from server, nbd_read_stat() will try to get request by tag, and then complete the request. However, this is problematic if nbd haven't sent a corresponding request message: t1 t2 submit_bio nbd_queue_rq blk_mq_start_request recv_work nbd_read_stat blk_mq_tag_to_rq blk_mq_complete_request nbd_send_cmd Thus add a new cmd flag 'NBD_CMD_INFLIGHT', it will be set in nbd_send_cmd() and checked in nbd_read_stat(). Noted that this patch can't fix that blk_mq_tag_to_rq() might return a freed request, and this will be fixed in following patches. Signed-off-by: Yu Kuai <yukuai3@huawei.com> Reviewed-by: Ming Lei <ming.lei@redhat.com> Reviewed-by: Josef Bacik <josef@toxicpanda.com> Link: https://lore.kernel.org/r/20210916093350.1410403-2-yukuai3@huawei.com Signed-off-by: Jens Axboe <axboe@kernel.dk> Reviewed-by: Jason Yan <yanaijie@huawei.com> Signed-off-by: Chen Jun <chenjun102@huawei.com> --- drivers/block/nbd.c | 22 +++++++++++++++++++++- 1 file changed, 21 insertions(+), 1 deletion(-) diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index 8a841d5f422d..cdee84f3c672 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -122,6 +122,12 @@ struct nbd_device { }; #define NBD_CMD_REQUEUED 1 +/* + * This flag will be set if nbd_queue_rq() succeed, and will be checked and + * cleared in completion. Both setting and clearing of the flag are protected + * by cmd->lock. + */ +#define NBD_CMD_INFLIGHT 2 struct nbd_cmd { struct nbd_device *nbd; @@ -389,6 +395,7 @@ static enum blk_eh_timer_return nbd_xmit_timeout(struct request *req, if (!mutex_trylock(&cmd->lock)) return BLK_EH_RESET_TIMER; + __clear_bit(NBD_CMD_INFLIGHT, &cmd->flags); if (!refcount_inc_not_zero(&nbd->config_refs)) { cmd->status = BLK_STS_TIMEOUT; mutex_unlock(&cmd->lock); @@ -718,6 +725,12 @@ static struct nbd_cmd *nbd_read_stat(struct nbd_device *nbd, int index) cmd = blk_mq_rq_to_pdu(req); mutex_lock(&cmd->lock); + if (!__test_and_clear_bit(NBD_CMD_INFLIGHT, &cmd->flags)) { + dev_err(disk_to_dev(nbd->disk), "Suspicious reply %d (status %u flags %lu)", + tag, cmd->status, cmd->flags); + ret = -ENOENT; + goto out; + } if (cmd->cmd_cookie != nbd_handle_to_cookie(handle)) { dev_err(disk_to_dev(nbd->disk), "Double reply on req %p, cmd_cookie %u, handle cookie %u\n", req, cmd->cmd_cookie, nbd_handle_to_cookie(handle)); @@ -817,6 +830,7 @@ static bool nbd_clear_req(struct request *req, void *data, bool reserved) return true; mutex_lock(&cmd->lock); + __clear_bit(NBD_CMD_INFLIGHT, &cmd->flags); cmd->status = BLK_STS_IOERR; mutex_unlock(&cmd->lock); @@ -953,7 +967,13 @@ static int nbd_handle_cmd(struct nbd_cmd *cmd, int index) * returns EAGAIN can be retried on a different socket. */ ret = nbd_send_cmd(nbd, cmd, index); - if (ret == -EAGAIN) { + /* + * Access to this flag is protected by cmd->lock, thus it's safe to set + * the flag after nbd_send_cmd() succeed to send request to server. + */ + if (!ret) + __set_bit(NBD_CMD_INFLIGHT, &cmd->flags); + else if (ret == -EAGAIN) { dev_err_ratelimited(disk_to_dev(nbd->disk), "Request send failed, requeueing\n"); nbd_mark_nsock_dead(nbd, nsock, 1); -- 2.20.1
From: Yu Kuai <yukuai3@huawei.com> mainline inclusion from mainline-next-20211018 commit d14b304f558f8c8f53da3a8d0c0b671f14a9c2f4 category: bugfix bugzilla: 49890 https://gitee.com/openeuler/kernel/issues/I4DDEL Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... --------------------------- commit cddce0116058 ("nbd: Aovid double completion of a request") try to fix that nbd_clear_que() and recv_work() can complete a request concurrently. However, the problem still exists: t1 t2 t3 nbd_disconnect_and_put flush_workqueue recv_work blk_mq_complete_request blk_mq_complete_request_remote -> this is true WRITE_ONCE(rq->state, MQ_RQ_COMPLETE) blk_mq_raise_softirq blk_done_softirq blk_complete_reqs nbd_complete_rq blk_mq_end_request blk_mq_free_request WRITE_ONCE(rq->state, MQ_RQ_IDLE) nbd_clear_que blk_mq_tagset_busy_iter nbd_clear_req __blk_mq_free_request blk_mq_put_tag blk_mq_complete_request -> complete again There are three places where request can be completed in nbd: recv_work(), nbd_clear_que() and nbd_xmit_timeout(). Since they all hold cmd->lock before completing the request, it's easy to avoid the problem by setting and checking a cmd flag. Signed-off-by: Yu Kuai <yukuai3@huawei.com> Reviewed-by: Ming Lei <ming.lei@redhat.com> Reviewed-by: Josef Bacik <josef@toxicpanda.com> Link: https://lore.kernel.org/r/20210916093350.1410403-3-yukuai3@huawei.com Signed-off-by: Jens Axboe <axboe@kernel.dk> Reviewed-by: Jason Yan <yanaijie@huawei.com> Signed-off-by: Chen Jun <chenjun102@huawei.com> --- drivers/block/nbd.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index cdee84f3c672..de6f6e0e9d3e 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -395,7 +395,11 @@ static enum blk_eh_timer_return nbd_xmit_timeout(struct request *req, if (!mutex_trylock(&cmd->lock)) return BLK_EH_RESET_TIMER; - __clear_bit(NBD_CMD_INFLIGHT, &cmd->flags); + if (!__test_and_clear_bit(NBD_CMD_INFLIGHT, &cmd->flags)) { + mutex_unlock(&cmd->lock); + return BLK_EH_DONE; + } + if (!refcount_inc_not_zero(&nbd->config_refs)) { cmd->status = BLK_STS_TIMEOUT; mutex_unlock(&cmd->lock); @@ -830,7 +834,10 @@ static bool nbd_clear_req(struct request *req, void *data, bool reserved) return true; mutex_lock(&cmd->lock); - __clear_bit(NBD_CMD_INFLIGHT, &cmd->flags); + if (!__test_and_clear_bit(NBD_CMD_INFLIGHT, &cmd->flags)) { + mutex_unlock(&cmd->lock); + return true; + } cmd->status = BLK_STS_IOERR; mutex_unlock(&cmd->lock); -- 2.20.1
From: Yu Kuai <yukuai3@huawei.com> mainline inclusion from mainline-next-20211018 commit dbd73178da676945d8bbcf6afe731623f683ce0a category: bugfix bugzilla: 49890 https://gitee.com/openeuler/kernel/issues/I4DDEL Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... --------------------------- The sock that clent send request in nbd_send_cmd() and receive reply in nbd_read_stat() should be the same. Signed-off-by: Yu Kuai <yukuai3@huawei.com> Reviewed-by: Ming Lei <ming.lei@redhat.com> Reviewed-by: Josef Bacik <josef@toxicpanda.com> Link: https://lore.kernel.org/r/20210916093350.1410403-4-yukuai3@huawei.com Signed-off-by: Jens Axboe <axboe@kernel.dk> Reviewed-by: Jason Yan <yanaijie@huawei.com> Signed-off-by: Chen Jun <chenjun102@huawei.com> --- drivers/block/nbd.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index de6f6e0e9d3e..264afd0d3614 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -735,6 +735,10 @@ static struct nbd_cmd *nbd_read_stat(struct nbd_device *nbd, int index) ret = -ENOENT; goto out; } + if (cmd->index != index) { + dev_err(disk_to_dev(nbd->disk), "Unexpected reply %d from different sock %d (expected %d)", + tag, index, cmd->index); + } if (cmd->cmd_cookie != nbd_handle_to_cookie(handle)) { dev_err(disk_to_dev(nbd->disk), "Double reply on req %p, cmd_cookie %u, handle cookie %u\n", req, cmd->cmd_cookie, nbd_handle_to_cookie(handle)); -- 2.20.1
From: Yu Kuai <yukuai3@huawei.com> mainline inclusion from mainline-next-20211018 commit a83fdc85365586dc5c0f3ff91680e18e37a66f19 category: bugfix bugzilla: 49890 https://gitee.com/openeuler/kernel/issues/I4DDEL Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... --------------------------- commit 6a468d5990ec ("nbd: don't start req until after the dead connection logic") move blk_mq_start_request() from nbd_queue_rq() to nbd_handle_cmd() to skip starting request if the connection is dead. However, request is still started in other error paths. Currently, blk_mq_end_request() will be called immediately if nbd_queue_rq() failed, thus start request in such situation is useless. So remove blk_mq_start_request() from error paths in nbd_handle_cmd(). Signed-off-by: Yu Kuai <yukuai3@huawei.com> Reviewed-by: Ming Lei <ming.lei@redhat.com> Reviewed-by: Josef Bacik <josef@toxicpanda.com> Link: https://lore.kernel.org/r/20210916093350.1410403-5-yukuai3@huawei.com Signed-off-by: Jens Axboe <axboe@kernel.dk> Reviewed-by: Jason Yan <yanaijie@huawei.com> Signed-off-by: Chen Jun <chenjun102@huawei.com> --- drivers/block/nbd.c | 3 --- 1 file changed, 3 deletions(-) diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index 264afd0d3614..e9d792d7e76b 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -923,7 +923,6 @@ static int nbd_handle_cmd(struct nbd_cmd *cmd, int index) if (!refcount_inc_not_zero(&nbd->config_refs)) { dev_err_ratelimited(disk_to_dev(nbd->disk), "Socks array is empty\n"); - blk_mq_start_request(req); return -EINVAL; } config = nbd->config; @@ -932,7 +931,6 @@ static int nbd_handle_cmd(struct nbd_cmd *cmd, int index) dev_err_ratelimited(disk_to_dev(nbd->disk), "Attempted send on invalid socket\n"); nbd_config_put(nbd); - blk_mq_start_request(req); return -EINVAL; } cmd->status = BLK_STS_OK; @@ -956,7 +954,6 @@ static int nbd_handle_cmd(struct nbd_cmd *cmd, int index) */ sock_shutdown(nbd); nbd_config_put(nbd); - blk_mq_start_request(req); return -EIO; } goto again; -- 2.20.1
From: Yu Kuai <yukuai3@huawei.com> mainline inclusion from mainline-next-20211018 commit 6157a8f489909db00151a4e361903b9099b03b75 category: bugfix bugzilla: 49890 https://gitee.com/openeuler/kernel/issues/I4DDEL Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... --------------------------- Check if sock_xmit() return 0 is useless because it'll never return 0, comment it and remove such checkings. Signed-off-by: Yu Kuai <yukuai3@huawei.com> Reviewed-by: Ming Lei <ming.lei@redhat.com> Reviewed-by: Josef Bacik <josef@toxicpanda.com> Link: https://lore.kernel.org/r/20210916093350.1410403-6-yukuai3@huawei.com Signed-off-by: Jens Axboe <axboe@kernel.dk> Reviewed-by: Jason Yan <yanaijie@huawei.com> Signed-off-by: Chen Jun <chenjun102@huawei.com> --- drivers/block/nbd.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index e9d792d7e76b..e69cc186d9a7 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -479,7 +479,8 @@ static enum blk_eh_timer_return nbd_xmit_timeout(struct request *req, } /* - * Send or receive packet. + * Send or receive packet. Return a positive value on success and + * negtive value on failue, and never return 0. */ static int sock_xmit(struct nbd_device *nbd, int index, int send, struct iov_iter *iter, int msg_flags, int *sent) @@ -605,7 +606,7 @@ static int nbd_send_cmd(struct nbd_device *nbd, struct nbd_cmd *cmd, int index) result = sock_xmit(nbd, index, 1, &from, (type == NBD_CMD_WRITE) ? MSG_MORE : 0, &sent); trace_nbd_header_sent(req, handle); - if (result <= 0) { + if (result < 0) { if (was_interrupted(result)) { /* If we havne't sent anything we can just return BUSY, * however if we have sent something we need to make @@ -649,7 +650,7 @@ static int nbd_send_cmd(struct nbd_device *nbd, struct nbd_cmd *cmd, int index) skip = 0; } result = sock_xmit(nbd, index, 1, &from, flags, &sent); - if (result <= 0) { + if (result < 0) { if (was_interrupted(result)) { /* We've already sent the header, we * have no choice but to set pending and @@ -701,7 +702,7 @@ static struct nbd_cmd *nbd_read_stat(struct nbd_device *nbd, int index) reply.magic = 0; iov_iter_kvec(&to, READ, &iov, 1, sizeof(reply)); result = sock_xmit(nbd, index, 0, &to, MSG_WAITALL, NULL); - if (result <= 0) { + if (result < 0) { if (!nbd_disconnected(config)) dev_err(disk_to_dev(nbd->disk), "Receive control failed (result %d)\n", result); @@ -772,7 +773,7 @@ static struct nbd_cmd *nbd_read_stat(struct nbd_device *nbd, int index) rq_for_each_segment(bvec, req, iter) { iov_iter_bvec(&to, READ, &bvec, 1, bvec.bv_len); result = sock_xmit(nbd, index, 0, &to, MSG_WAITALL, NULL); - if (result <= 0) { + if (result < 0) { dev_err(disk_to_dev(nbd->disk), "Receive data failed (result %d)\n", result); /* @@ -1218,7 +1219,7 @@ static void send_disconnects(struct nbd_device *nbd) iov_iter_kvec(&from, WRITE, &iov, 1, sizeof(request)); mutex_lock(&nsock->tx_lock); ret = sock_xmit(nbd, i, 1, &from, 0, NULL); - if (ret <= 0) + if (ret < 0) dev_err(disk_to_dev(nbd->disk), "Send disconnect failed %d\n", ret); mutex_unlock(&nsock->tx_lock); -- 2.20.1
From: Yu Kuai <yukuai3@huawei.com> mainline inclusion from mainline-next-20211018 commit 961e9f50be9bb47835b0ac7e08d55d2d0a45e493 category: bugfix bugzilla: 49890 https://gitee.com/openeuler/kernel/issues/I4DDEL Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... --------------------------- Prepare to fix uaf in nbd_read_stat(), no functional changes. Signed-off-by: Yu Kuai <yukuai3@huawei.com> Reviewed-by: Ming Lei <ming.lei@redhat.com> Reviewed-by: Josef Bacik <josef@toxicpanda.com> Link: https://lore.kernel.org/r/20210916093350.1410403-7-yukuai3@huawei.com Signed-off-by: Jens Axboe <axboe@kernel.dk> Reviewed-by: Jason Yan <yanaijie@huawei.com> Signed-off-by: Chen Jun <chenjun102@huawei.com> --- drivers/block/nbd.c | 74 +++++++++++++++++++++++++++------------------ 1 file changed, 44 insertions(+), 30 deletions(-) diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index e69cc186d9a7..e0cf833cd780 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -684,38 +684,45 @@ static int nbd_send_cmd(struct nbd_device *nbd, struct nbd_cmd *cmd, int index) return 0; } -/* NULL returned = something went wrong, inform userspace */ -static struct nbd_cmd *nbd_read_stat(struct nbd_device *nbd, int index) +static int nbd_read_reply(struct nbd_device *nbd, int index, + struct nbd_reply *reply) { - struct nbd_config *config = nbd->config; - int result; - struct nbd_reply reply; - struct nbd_cmd *cmd; - struct request *req = NULL; - u64 handle; - u16 hwq; - u32 tag; - struct kvec iov = {.iov_base = &reply, .iov_len = sizeof(reply)}; + struct kvec iov = {.iov_base = reply, .iov_len = sizeof(*reply)}; struct iov_iter to; - int ret = 0; + int result; - reply.magic = 0; - iov_iter_kvec(&to, READ, &iov, 1, sizeof(reply)); + reply->magic = 0; + iov_iter_kvec(&to, READ, &iov, 1, sizeof(*reply)); result = sock_xmit(nbd, index, 0, &to, MSG_WAITALL, NULL); if (result < 0) { - if (!nbd_disconnected(config)) + if (!nbd_disconnected(nbd->config)) dev_err(disk_to_dev(nbd->disk), "Receive control failed (result %d)\n", result); - return ERR_PTR(result); + return result; } - if (ntohl(reply.magic) != NBD_REPLY_MAGIC) { + if (ntohl(reply->magic) != NBD_REPLY_MAGIC) { dev_err(disk_to_dev(nbd->disk), "Wrong magic (0x%lx)\n", - (unsigned long)ntohl(reply.magic)); - return ERR_PTR(-EPROTO); + (unsigned long)ntohl(reply->magic)); + return -EPROTO; } - memcpy(&handle, reply.handle, sizeof(handle)); + return 0; +} + +/* NULL returned = something went wrong, inform userspace */ +static struct nbd_cmd *nbd_handle_reply(struct nbd_device *nbd, int index, + struct nbd_reply *reply) +{ + int result; + struct nbd_cmd *cmd; + struct request *req = NULL; + u64 handle; + u16 hwq; + u32 tag; + int ret = 0; + + memcpy(&handle, reply->handle, sizeof(handle)); tag = nbd_handle_to_tag(handle); hwq = blk_mq_unique_tag_to_hwq(tag); if (hwq < nbd->tag_set.nr_hw_queues) @@ -758,9 +765,9 @@ static struct nbd_cmd *nbd_read_stat(struct nbd_device *nbd, int index) ret = -ENOENT; goto out; } - if (ntohl(reply.error)) { + if (ntohl(reply->error)) { dev_err(disk_to_dev(nbd->disk), "Other side returned error (%d)\n", - ntohl(reply.error)); + ntohl(reply->error)); cmd->status = BLK_STS_IOERR; goto out; } @@ -769,6 +776,7 @@ static struct nbd_cmd *nbd_read_stat(struct nbd_device *nbd, int index) if (rq_data_dir(req) != WRITE) { struct req_iterator iter; struct bio_vec bvec; + struct iov_iter to; rq_for_each_segment(bvec, req, iter) { iov_iter_bvec(&to, READ, &bvec, 1, bvec.bv_len); @@ -782,7 +790,7 @@ static struct nbd_cmd *nbd_read_stat(struct nbd_device *nbd, int index) * and let the timeout stuff handle resubmitting * this request onto another connection. */ - if (nbd_disconnected(config)) { + if (nbd_disconnected(nbd->config)) { cmd->status = BLK_STS_IOERR; goto out; } @@ -806,24 +814,30 @@ static void recv_work(struct work_struct *work) work); struct nbd_device *nbd = args->nbd; struct nbd_config *config = nbd->config; + struct nbd_sock *nsock; struct nbd_cmd *cmd; struct request *rq; while (1) { - cmd = nbd_read_stat(nbd, args->index); - if (IS_ERR(cmd)) { - struct nbd_sock *nsock = config->socks[args->index]; + struct nbd_reply reply; - mutex_lock(&nsock->tx_lock); - nbd_mark_nsock_dead(nbd, nsock, 1); - mutex_unlock(&nsock->tx_lock); + if (nbd_read_reply(nbd, args->index, &reply)) + break; + + cmd = nbd_handle_reply(nbd, args->index, &reply); + if (IS_ERR(cmd)) break; - } rq = blk_mq_rq_from_pdu(cmd); if (likely(!blk_should_fake_timeout(rq->q))) blk_mq_complete_request(rq); } + + nsock = config->socks[args->index]; + mutex_lock(&nsock->tx_lock); + nbd_mark_nsock_dead(nbd, nsock, 1); + mutex_unlock(&nsock->tx_lock); + nbd_config_put(nbd); atomic_dec(&config->recv_threads); wake_up(&config->recv_wq); -- 2.20.1
From: Yu Kuai <yukuai3@huawei.com> mainline inclusion from mainline-next-20211018 commit 52c90e0184f67eecb00b53b79bfdf75e0274f8fd category: bugfix bugzilla: 49890 https://gitee.com/openeuler/kernel/issues/I4DDEL Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... --------------------------- There is a problem that nbd_handle_reply() might access freed request: 1) At first, a normal io is submitted and completed with scheduler: internal_tag = blk_mq_get_tag -> get tag from sched_tags blk_mq_rq_ctx_init sched_tags->rq[internal_tag] = sched_tag->static_rq[internal_tag] ... blk_mq_get_driver_tag __blk_mq_get_driver_tag -> get tag from tags tags->rq[tag] = sched_tag->static_rq[internal_tag] So, both tags->rq[tag] and sched_tags->rq[internal_tag] are pointing to the request: sched_tags->static_rq[internal_tag]. Even if the io is finished. 2) nbd server send a reply with random tag directly: recv_work nbd_handle_reply blk_mq_tag_to_rq(tags, tag) rq = tags->rq[tag] 3) if the sched_tags->static_rq is freed: blk_mq_sched_free_requests blk_mq_free_rqs(q->tag_set, hctx->sched_tags, i) -> step 2) access rq before clearing rq mapping blk_mq_clear_rq_mapping(set, tags, hctx_idx); __free_pages() -> rq is freed here 4) Then, nbd continue to use the freed request in nbd_handle_reply Fix the problem by get 'q_usage_counter' before blk_mq_tag_to_rq(), thus request is ensured not to be freed because 'q_usage_counter' is not zero. Signed-off-by: Yu Kuai <yukuai3@huawei.com> Reviewed-by: Ming Lei <ming.lei@redhat.com> Link: https://lore.kernel.org/r/20210916141810.2325276-1-yukuai3@huawei.com Signed-off-by: Jens Axboe <axboe@kernel.dk> Reviewed-by: Jason Yan <yanaijie@huawei.com> Signed-off-by: Chen Jun <chenjun102@huawei.com> --- drivers/block/nbd.c | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-) diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index e0cf833cd780..fe635bc3e8c4 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -814,6 +814,7 @@ static void recv_work(struct work_struct *work) work); struct nbd_device *nbd = args->nbd; struct nbd_config *config = nbd->config; + struct request_queue *q = nbd->disk->queue; struct nbd_sock *nsock; struct nbd_cmd *cmd; struct request *rq; @@ -824,13 +825,28 @@ static void recv_work(struct work_struct *work) if (nbd_read_reply(nbd, args->index, &reply)) break; + /* + * Grab .q_usage_counter so request pool won't go away, then no + * request use-after-free is possible during nbd_handle_reply(). + * If queue is frozen, there won't be any inflight requests, we + * needn't to handle the incoming garbage message. + */ + if (!percpu_ref_tryget(&q->q_usage_counter)) { + dev_err(disk_to_dev(nbd->disk), "%s: no io inflight\n", + __func__); + break; + } + cmd = nbd_handle_reply(nbd, args->index, &reply); - if (IS_ERR(cmd)) + if (IS_ERR(cmd)) { + percpu_ref_put(&q->q_usage_counter); break; + } rq = blk_mq_rq_from_pdu(cmd); if (likely(!blk_should_fake_timeout(rq->q))) blk_mq_complete_request(rq); + percpu_ref_put(&q->q_usage_counter); } nsock = config->socks[args->index]; -- 2.20.1
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Zheng Zengkai