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1f032ca298
[ Upstream commit 7ce23e8e0a ]
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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.