CVE-2022-49412
Published: 26 February 2025
Description
In the Linux kernel, the following vulnerability has been resolved: bfq: Avoid merging queues with different parents It can happen that the parent of a bfqq changes between the moment we decide two queues are worth to merge (and set bic->stable_merge_bfqq) and the moment bfq_setup_merge() is called. This can happen e.g. because the process submitted IO for a different cgroup and thus bfqq got reparented. It can even happen that the bfqq we are merging with has parent cgroup that is already offline and going to be destroyed in which case the merge can lead to use-after-free issues such as: BUG: KASAN: use-after-free in __bfq_deactivate_entity+0x9cb/0xa50 Read of size 8 at addr ffff88800693c0c0 by task runc:[2:INIT]/10544 CPU: 0 PID: 10544 Comm: runc:[2:INIT] Tainted: G E 5.15.2-0.g5fb85fd-default #1 openSUSE Tumbleweed (unreleased) f1f3b891c72369aebecd2e43e4641a6358867c70 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a-rebuilt.opensuse.org 04/01/2014 Call Trace: <IRQ> dump_stack_lvl+0x46/0x5a print_address_description.constprop.0+0x1f/0x140 ? __bfq_deactivate_entity+0x9cb/0xa50 kasan_report.cold+0x7f/0x11b ? __bfq_deactivate_entity+0x9cb/0xa50 __bfq_deactivate_entity+0x9cb/0xa50 ? update_curr+0x32f/0x5d0 bfq_deactivate_entity+0xa0/0x1d0 bfq_del_bfqq_busy+0x28a/0x420 ? resched_curr+0x116/0x1d0 ? bfq_requeue_bfqq+0x70/0x70 ? check_preempt_wakeup+0x52b/0xbc0 __bfq_bfqq_expire+0x1a2/0x270 bfq_bfqq_expire+0xd16/0x2160 ? try_to_wake_up+0x4ee/0x1260 ? bfq_end_wr_async_queues+0xe0/0xe0 ? _raw_write_unlock_bh+0x60/0x60 ? _raw_spin_lock_irq+0x81/0xe0 bfq_idle_slice_timer+0x109/0x280 ? bfq_dispatch_request+0x4870/0x4870 __hrtimer_run_queues+0x37d/0x700 ? enqueue_hrtimer+0x1b0/0x1b0 ? kvm_clock_get_cycles+0xd/0x10 ? ktime_get_update_offsets_now+0x6f/0x280 hrtimer_interrupt+0x2c8/0x740 Fix the problem by checking that the parent of the two bfqqs we are merging in bfq_setup_merge() is the same.
Security Summary
CVE-2022-49412 is a use-after-free vulnerability in the BFQ I/O scheduler of the Linux kernel. The issue arises when the parent of a BFQ queue (bfqq) changes between the decision to merge two queues and the execution of bfq_setup_merge(), such as when a process submits I/O to a different cgroup, causing reparenting. This can lead to merging with a queue whose parent cgroup is offline and being destroyed, resulting in use-after-free errors, as detected by KASAN in functions like __bfq_deactivate_entity.
A local attacker with low privileges (AV:L/AC:L/PR:L/UI:N) can exploit this vulnerability. Successful exploitation could grant high-impact confidentiality, integrity, and availability effects (C:H/I:H/A:H), potentially allowing arbitrary code execution, system crashes, or data corruption through the use-after-free condition triggered during queue merging and deactivation.
Mitigation is provided via kernel patches available in stable releases, such as commits 5ee21edaed09e6b25f2c007b3f326752bc89bacf, 8abc8763b11c35e03cc91d59fd0cd28d39f88ca9, a16c65cca7d2c7ff965fdd3adc8df2156529caf1, and c1cee4ab36acef271be9101590756ed0c0c374d9. These patches fix the issue by verifying that the parents of the two bfqqs match before merging in bfq_setup_merge(). Security practitioners should update affected Linux kernels to incorporate these fixes.
Details
- CWE(s)