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| author | Josef Bacik <josef@toxicpanda.com> | 2019-10-21 15:56:28 -0400 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2019-10-25 14:20:03 -0600 |
| commit | 7ce23e8e0a9cd38338fc8316ac5772666b565ca9 (patch) | |
| tree | 117afaef6338f724012b32af81fdaac6c0714223 | |
| parent | de6346ecbc8f5591ebd6c44ac164e8b8671d71d7 (diff) | |
| download | linux-7ce23e8e0a9cd38338fc8316ac5772666b565ca9.tar.bz2 | |
nbd: handle racing with error'ed out commands
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.
Reviewed-by: Mike Christie <mchristi@redhat.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
| -rw-r--r-- | drivers/block/nbd.c | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index f9e189534304..e200c7c9ddc4 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -710,6 +710,12 @@ 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); |