block, bfq: fix possible uaf for 'bfqq->bic'
Published Oct 4, 2025
7.8
HIGHCVSS 3.1
EPSS 0.16%
Description
Our test report a uaf for 'bfqq->bic' in 5.10:
================================================================== BUG: KASAN: use-after-free in bfq_select_queue+0x378/0xa30
CPU: 6 PID: 2318352 Comm: fsstress Kdump: loaded Not tainted 5.10.0-60.18.0.50.h602.kasan.eulerosv2r11.x86_64 #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.1-0-ga5cab58-20220320_160524-szxrtosci10000 04/01/2014 Call Trace: bfq_select_queue+0x378/0xa30 bfq_dispatch_request+0xe8/0x130 blk_mq_do_dispatch_sched+0x62/0xb0 __blk_mq_sched_dispatch_requests+0x215/0x2a0 blk_mq_sched_dispatch_requests+0x8f/0xd0 __blk_mq_run_hw_queue+0x98/0x180 __blk_mq_delay_run_hw_queue+0x22b/0x240 blk_mq_run_hw_queue+0xe3/0x190 blk_mq_sched_insert_requests+0x107/0x200 blk_mq_flush_plug_list+0x26e/0x3c0 blk_finish_plug+0x63/0x90 __iomap_dio_rw+0x7b5/0x910 iomap_dio_rw+0x36/0x80 ext4_dio_read_iter+0x146/0x190 [ext4] ext4_file_read_iter+0x1e2/0x230 [ext4] new_sync_read+0x29f/0x400 vfs_read+0x24e/0x2d0 ksys_read+0xd5/0x1b0 do_syscall_64+0x33/0x40 entry_SYSCALL_64_after_hwframe+0x61/0xc6
Commit 3bc5e683c67d ("bfq: Split shared queues on move between cgroups") changes that move process to a new cgroup will allocate a new bfqq to use, however, the old bfqq and new bfqq can point to the same bic:
1) Initial state, two process with io in the same cgroup.
Process 1 Process 2 (BIC1) (BIC2) | Λ | Λ | | | | V | V | bfqq1 bfqq2
2) bfqq1 is merged to bfqq2.
Process 1 Process 2 (BIC1) (BIC2) | | \-------------\| V bfqq1 bfqq2(coop)
3) Process 1 exit, then issue new io(denoce IOA) from Process 2.
(BIC2) | Λ | | V | bfqq2(coop)
4) Before IOA is completed, move Process 2 to another cgroup and issue io.
Process 2 (BIC2) Λ |\--------------\ | V bfqq2 bfqq3
Now that BIC2 points to bfqq3, while bfqq2 and bfqq3 both point to BIC2. If all the requests are completed, and Process 2 exit, BIC2 will be freed while there is no guarantee that bfqq2 will be freed before BIC2.
Fix the problem by clearing bfqq->bic while bfqq is detached from bic.
Affected products
-
- Version StatusaffectedConstraints-
- Version StatusaffectedConstraints
- Version StatusaffectedConstraints
- Version StatusaffectedConstraints
- Version StatusaffectedConstraints-
- Version StatusaffectedConstraints
- Version StatusaffectedConstraints
- Version StatusaffectedConstraints-
- Version
-
- Version 5.10.121StatusaffectedConstraints<5.10.175
- Version 5.15.46StatusaffectedConstraints<5.15.86
- Version 5.17.14StatusaffectedConstraints<5.18
- Version 5.18.3StatusaffectedConstraints<5.19
- Version 5.4.198StatusaffectedConstraints<5.5
- Version
-
- Version 5.19StatusaffectedConstraints-
- Version 0StatusunaffectedConstraints<5.19
- Version 5.10.175StatusunaffectedConstraints<=5.10.*
- Version 5.15.86StatusunaffectedConstraints<=5.15.*
- Version 6.0.16StatusunaffectedConstraints<=6.0.*
- Version 6.1.2StatusunaffectedConstraints<=6.1.*
- Version 6.2StatusunaffectedConstraints<=*
- Version
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | |||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Linux | Linux | unaffected |
| |||||||||||||||||||||||||||
| Linux | Linux | unaffected |
| |||||||||||||||||||||||||||
| Linux | Linux | affected |
|
- ≥ 5.4.198 · < 5.5
- ≥ 5.10.121 · < 5.10.175
- ≥ 5.15.46 · < 5.15.86
- ≥ 5.17.14 · < 5.18
- ≥ 5.18.3 · < 6.0.16
- ≥ 6.1 · < 6.1.2
No data.
Red Hat Enterprise Linux 10
kernel
Not affected
Red Hat Enterprise Linux 6
kernel
Not affected
Red Hat Enterprise Linux 7
kernel
Not affected
Red Hat Enterprise Linux 7
kernel-rt
Not affected
Red Hat Enterprise Linux 8
kernel
Not affected
Red Hat Enterprise Linux 8
kernel-rt
Not affected
Red Hat Enterprise Linux 9
kernel
Fix deferred
Red Hat Enterprise Linux 9
kernel-rt
Fix deferred
| Product | Package | State | Advisory |
|---|---|---|---|
| Red Hat Enterprise Linux 10 | kernel | Not affected | n/a |
| Red Hat Enterprise Linux 6 | kernel | Not affected | n/a |
| Red Hat Enterprise Linux 7 | kernel | Not affected | n/a |
| Red Hat Enterprise Linux 7 | kernel-rt | Not affected | n/a |
| Red Hat Enterprise Linux 8 | kernel | Not affected | n/a |
| Red Hat Enterprise Linux 8 | kernel-rt | Not affected | n/a |
| Red Hat Enterprise Linux 9 | kernel | Fix deferred | n/a |
| Red Hat Enterprise Linux 9 | kernel-rt | Fix deferred | n/a |
No package ranges for this CVE.
Remediation
Red Hat statement
On Red Hat Enterprise Linux 9, regular (non-root) users cannot exploit this vulnerability. This is due to the following: 1) By default, SELinux actively enforces policies in targeted mode, meaning that even if base permissions allow cgroup manipulation, unprivileged cgroup manipulation will be prevented. 2) By default, systemd does not delegate cgroup control to user processes, meaning that user sessions and services cannot create or manage their own cgroup hierarchies.
Metrics
No CVSS v4.0 score for this CVE.
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
1 other source (Red Hat) ▾
CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:H/A:H
No CVSS v3.0 score for this CVE.
No CVSS v2.0 score for this CVE.
This CVE is not in the KEV list.
No CISA SSVC assessment for this CVE yet.
Estimated probability of exploitation in the wild in the next 30 days (FIRST EPSS). As of Oct 1, 2026.
Score over time
2025–2026- EPSS v4
- EPSS v5
Percentile over time
- EPSS v4
- EPSS v5
Table of values (3 key points)
Flat stretches are collapsed; showing up to 120 newest points.
| Date | Score | Percentile | Model |
|---|---|---|---|
| Oct 1, 2026 | 0.16% (0.00163) | 4.90th | v5 (v2026.06.15) |
| Jun 15, 2026 | 0.15% (0.00149) | 4.47th | v5 (v2026.06.15) |
| Oct 5, 2025 | 0.02% (0.00018) | 3.30th | v4 (v2025.03.14) |
References (10)
- https://access.redhat.com/security/cve/CVE-2022-50488 Vendor Advisory
- https://bugzilla.redhat.com/show_bug.cgi?id=2401551 Issue Tracking
- https://git.kernel.org/stable/c/094f3d9314d67691cb21ba091c1b528f6e3c4893 Patch
- https://git.kernel.org/stable/c/5533742c7cb1bc9b1f0bf401cc397d44a3a9e07a Patch
- https://git.kernel.org/stable/c/64dc8c732f5c2b406cc752e6aaa1bd5471159cab Patch
- https://git.kernel.org/stable/c/761564d93c8265f65543acf0a576b32d66bfa26a Patch
- https://git.kernel.org/stable/c/b22fd72bfebda3956efc4431b60ddfc0a51e03e0 Patch
- https://lore.kernel.org/linux-cve-announce/2025100413-CVE-2022-50488-32e8@gregkh/T
- https://nvd.nist.gov/vuln/detail/CVE-2022-50488
- https://www.cve.org/CVERecord?id=CVE-2022-50488
Change history (0)
No recorded changes yet.