Riskcovery

CVE-2022-50488

block, bfq: fix possible uaf for 'bfqq->bic'

State
Published
Severity
7.8 High
Published
Oct 4, 2025
Updated
Oct 15, 2026
Reserved
Oct 4, 2025

Read the record on cve.org

Description

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

block, bfq: fix possible uaf for 'bfqq->bic'

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.

Scores

CVSSScoreVectorSource
3.17.8 HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HLinux

Weaknesses

The record names no weakness.

Affected Products

ProductVersions
LinuxLinux
  • 4dfc12f8c94c8052e975060f595938f75e8b7165 to before 5533742c7cb1bc9b1f0bf401cc397d44a3a9e07aAffected
  • 81b7d0c717a487ec50e2924a773ff501ee40f0d5 to before 094f3d9314d67691cb21ba091c1b528f6e3c4893Affected
  • 3bc5e683c67d94bd839a1da2e796c15847b51b69 to before b22fd72bfebda3956efc4431b60ddfc0a51e03e0Affected
  • 3bc5e683c67d94bd839a1da2e796c15847b51b69 to before 761564d93c8265f65543acf0a576b32d66bfa26aAffected
  • 3bc5e683c67d94bd839a1da2e796c15847b51b69 to before 64dc8c732f5c2b406cc752e6aaa1bd5471159cabAffected
  • 31326bf551269fb9bafa84ca99172b8340e5d8f8Affected
  • 43c51b86dbe551cff5d39b88aa2f41d29479f9c4Affected
  • 8615f6c0c9e7cf0ca90b6b5408784d797cbe5621Affected
  • 5.10.121 to before 5.10.175Affected
  • 5.15.46 to before 5.15.86Affected
  • 5.4.198 to before 5.5Affected
  • 5.17.14 to before 5.18Affected
  • 5.18.3 to before 5.19Affected
LinuxLinux
  • 5.19Affected
  • before 5.19Not affected
  • 5.10.175 through 5.10.*Not affected
  • 5.15.86 through 5.15.*Not affected
  • 6.0.16 through 6.0.*Not affected
  • 6.1.2 through 6.1.*Not affected
  • 6.2 and laterNot affected

References

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