CVE-2022-50488
Unknown Unknown - Not Provided
BaseFortify

Publication date: 2025-10-04

Last updated on: 2026-03-25

Assigner: kernel.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) | Ξ› | Ξ› | | | | 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) | Ξ› | | V | bfqq2(coop) 4) Before IOA is completed, move Process 2 to another cgroup and issue io. Process 2 (BIC2) Ξ› |\--------------\ | 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.
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Meta Information
Published
2025-10-04
Last Modified
2026-03-25
Generated
2026-05-06
AI Q&A
2025-10-04
EPSS Evaluated
2026-05-05
NVD
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel 5.10
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-UNKNOWN
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AI Powered Q&A
Can you explain this vulnerability to me?

This vulnerability is a use-after-free (UAF) issue in the Linux kernel's block layer, specifically related to the bfq (Budget Fair Queueing) I/O scheduler. It occurs when the bfqq structure's pointer to bic (bfqq->bic) is not properly cleared when bfqq is detached from bic. This can lead to a situation where the bic structure is freed while bfqq still holds a reference to it, causing a use-after-free error. The problem arises during process movements between control groups (cgroups) and I/O operations, where multiple bfqq and bic pointers can become inconsistently linked, leading to potential memory corruption or crashes.


How can this vulnerability impact me? :

This use-after-free vulnerability can lead to memory corruption in the Linux kernel, which may cause system instability, crashes, or potentially allow an attacker to execute arbitrary code with kernel privileges. Such impacts can compromise system reliability and security, especially on systems heavily using cgroups and the bfq I/O scheduler.


What immediate steps should I take to mitigate this vulnerability?

The vulnerability is fixed in the Linux kernel by clearing bfqq->bic while bfqq is detached from bic to prevent use-after-free. Immediate mitigation involves updating your Linux kernel to a version that includes this fix (post commit 3bc5e683c67d).


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