[stable request] block: stop the timeout timer when releasing a never added disk

[stable request] block: stop the timeout timer when releasing a never added disk

[Chao Shi]

Hi,

Please consider the following mainline commit for the stable trees:

  26cb8ebbfaf7 ("block: stop the timeout timer when releasing a never
  added disk")

It first appeared in v7.2-rc6 and shipped in v7.2.

Why it should be applied
------------------------

disk_release() undoes blk_mq_init_allocated_queue() for a disk whose
probe failed before add_disk(), but it only calls blk_mq_exit_queue().
Nothing there stops q->timeout, and that timer rolls forward: it stays
pending until it next expires, not until the last request completes.  So
if the driver issued any I/O before adding the disk, the request_queue
is freed while still linked into a timer wheel bucket.

That is a use-after-free.  With KASAN it is reported in
detach_if_pending(), enqueue_timer() or __run_timers(); without KASAN it
shows up as a general protection fault in the timer wheel, in a task
unrelated to the driver that leaked the timer.

  BUG: KASAN: slab-use-after-free in detach_if_pending+0x30c/0x340
  Write of size 8 at addr ffff888004d71310 by task kworker/u8:2/37
   __timer_delete_sync+0x156/0x240 kernel/time/timer.c:1621
   blk_sync_queue+0x22/0x40 block/blk-core.c:222
   nvme_sync_queues+0x100/0x150 drivers/nvme/host/core.c:5362
   nvme_reset_work+0x138/0x930 drivers/nvme/host/pci.c:3264

nvme reaches it because nvme_update_ns_info() submits Report Zones or
FDP io-mgmt-recv on ns->queue before the disk is added, so a later
failure lands in put_disk() with the timer still armed.

Which trees
-----------

All supported branches from 6.1.y up: 7.1.y, 6.18.y, 6.12.y, 6.6.y and
6.1.y.

The regression was introduced by 6f8191fdf41d ("block: simplify disk
shutdown"), which is v6.0, so 5.15.y and 5.10.y are not affected and
should be skipped.

Backport notes
--------------

The commit applies cleanly to all five branches (checked with
git apply --check against block/genhd.c from each branch), so no
backport is needed.  The two helpers it adds calls to, blk_sync_queue()
and blk_mq_cancel_work_sync(), are already called from block/genhd.c on
every one of those branches.

Thanks,
Chao

Re: [stable request] block: stop the timeout timer when releasing a never added disk

[Sasha Levin]

On Mon, Aug 17, 2026 at 03:58:27PM -0400, Chao Shi wrote:
> Please consider the following mainline commit for the stable trees:
>
>   26cb8ebbfaf7 ("block: stop the timeout timer when releasing a never
>   added disk")

Queued for 7.1, 6.18, 6.12, 6.6 and 6.1, thanks.

-- 
Thanks,
Sasha