CVE-2024-36908

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.

Affected Software

References

• https://git.kernel.org/stable/c/01bc4fda9ea0a6b52f12326486f07a4910666cf6
• https://git.kernel.org/stable/c/14b3275f93d4a0d8ddc02195bc4e9869b7a3700e
• https://git.kernel.org/stable/c/1c172ac7afe4442964f4153b2c78fe4e005d9d67