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.
CVSS Details
- CVSS 3.1 Base Score: 7.8
- CVSS 3.1 Vector: (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H)
Covered by Rapid7
| Product | Vendor Advisory | Solution File | Added | Published |
|---|---|---|---|---|
| Amazon Linux Ami 2 | — | Upgrade perfUpgrade kernel-headersUpgrade kernel-tools-develUpgrade perf-debuginfoUpgrade python-perf-debuginfoUpgrade kernel-tools-debuginfoUpgrade kernel-toolsUpgrade bpftool-debuginfoUpgrade kernel-debuginfo-common-aarch64Upgrade bpftoolUpgrade kernel-develUpgrade kernel-livepatch-5.15.50-23.125Upgrade kernel-debuginfo-common-x86_64Upgrade kernel-debuginfoUpgrade kernelUpgrade python-perf | Mar 14, 2025 | Feb 26, 2025 |
| Debian | — | Upgrade linux | Feb 27, 2025 | Feb 27, 2025 |
| Redhat_linux | — | No solution exists | Jul 9, 2025 | Feb 26, 2025 |
| Ubuntu | — | Upgrade linux-gcpUpgrade linux-realtimeUpgrade linux-hwe-5.15Upgrade linux-lowlatency-hwe-5.15Upgrade linux-awsUpgrade linuxUpgrade linux-azureUpgrade linux-aws-5.15Upgrade linux-gkeopUpgrade linux-gkeUpgrade linux-riscv-5.15Upgrade linux-ibmUpgrade linux-lowlatencyUpgrade linux-oracle-5.15Upgrade linux-nvidiaUpgrade linux-kvmUpgrade linux-azure-5.15Upgrade linux-intel-iotg-5.15Upgrade linux-gcp-5.15Upgrade linux-raspiUpgrade linux-oracleUpgrade linux-intel-iotg | Mar 19, 2025 | Feb 26, 2025 |
| Vmware Photon_os | — | Use 'tdnf update' to upgrade all packages to the latest version. | May 27, 2026 | Feb 26, 2025 |
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