In the Linux kernel, the following vulnerability has been resolved:

blk-iocost: do not WARN if iocg was already offlined

In iocg_pay_debt(), warn is triggered if 'active_list' is empty, which
is intended to confirm iocg is active when it has debt. However, warn
can be triggered during a blkcg or disk removal, if iocg_waitq_timer_fn()
is run at that time:

  WARNING: CPU: 0 PID: 2344971 at block/blk-iocost.c:1402 iocg_pay_debt+0x14c/0x190
  Call trace:
  iocg_pay_debt+0x14c/0x190
  iocg_kick_waitq+0x438/0x4c0
  iocg_waitq_timer_fn+0xd8/0x130
  __run_hrtimer+0x144/0x45c
  __hrtimer_run_queues+0x16c/0x244
  hrtimer_interrupt+0x2cc/0x7b0

The warn in this situation is meaningless. Since this iocg is being
removed, the state of the 'active_list' is irrelevant, and 'waitq_timer'
is canceled after removing 'active_list' in ioc_pd_free(), which ensures
iocg is freed after iocg_waitq_timer_fn() returns.

Therefore, add the check if iocg was already offlined to avoid warn
when removing a blkcg or disk.

kernel.org https://git.kernel.org/stable/c/01bc4fda9ea0a6b52f12326486f07a4910666cf6 [No types assigned]

kernel.org https://git.kernel.org/stable/c/14b3275f93d4a0d8ddc02195bc4e9869b7a3700e [No types assigned]

kernel.org https://git.kernel.org/stable/c/1c172ac7afe4442964f4153b2c78fe4e005d9d67 [No types assigned]