| Message ID | 20191021195628.19849-3-josef@toxicpanda.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | fix double completion of timed out commands | expand |
diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index 8fb8913074b8..e9f5d4e476e7 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -693,6 +693,12 @@ static struct nbd_cmd *nbd_read_stat(struct nbd_device *nbd, int index) ret = -ENOENT; goto out; } + if (cmd->status != BLK_STS_OK) { + dev_err(disk_to_dev(nbd->disk), "Command already handled %p\n", + req); + ret = -ENOENT; + goto out; + } if (test_bit(NBD_CMD_REQUEUED, &cmd->flags)) { dev_err(disk_to_dev(nbd->disk), "Raced with timeout on req %p\n", req);
We hit the following warning in production print_req_error: I/O error, dev nbd0, sector 7213934408 flags 80700 ------------[ cut here ]------------ refcount_t: underflow; use-after-free. WARNING: CPU: 25 PID: 32407 at lib/refcount.c:190 refcount_sub_and_test_checked+0x53/0x60 Workqueue: knbd-recv recv_work [nbd] RIP: 0010:refcount_sub_and_test_checked+0x53/0x60 Call Trace: blk_mq_free_request+0xb7/0xf0 blk_mq_complete_request+0x62/0xf0 recv_work+0x29/0xa1 [nbd] process_one_work+0x1f5/0x3f0 worker_thread+0x2d/0x3d0 ? rescuer_thread+0x340/0x340 kthread+0x111/0x130 ? kthread_create_on_node+0x60/0x60 ret_from_fork+0x1f/0x30 ---[ end trace b079c3c67f98bb7c ]--- This was preceded by us timing out everything and shutting down the sockets for the device. The problem is we had a request in the queue at the same time, so we completed the request twice. This can actually happen in a lot of cases, we fail to get a ref on our config, we only have one connection and just error out the command, etc. Fix this by checking cmd->status in nbd_read_stat. We only change this under the cmd->lock, so we are safe to check this here and see if we've already error'ed this command out, which would indicate that we've completed it as well. Signed-off-by: Josef Bacik <josef@toxicpanda.com> --- drivers/block/nbd.c | 6 ++++++ 1 file changed, 6 insertions(+)