CVE-2023-53111: loop: Fix use-after-free issues

Severity: high (CVSS 7.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-05-02 · updated 2026-10-30
Weakness: CWE-416

Description

In the Linux kernel, the following vulnerability has been resolved: loop: Fix use-after-free issues do_req_filebacked() calls blk_mq_complete_request() synchronously or asynchronously when using asynchronous I/O unless memory allocation fails. Hence, modify loop_handle_cmd() such that it does not dereference 'cmd' nor 'rq' after do_req_filebacked() finished unless we are sure that the request has not yet been completed. This patch fixes the following kernel crash: Unable to handle kernel NULL pointer dereference at virtual address 0000000000000054 Call trace: css_put.42938+0x1c/0x1ac loop_process_work+0xc8c/0xfd4 loop_rootcg_workfn+0x24/0x34 process_one_work+0x244/0x558 worker_thread+0x400/0x8fc kthread+0x16c/0x1e0 ret_from_fork+0x10/0x20

Affected products

Linux kernel: from 4.4 before 5.15.104; from 5.16 before 6.1.21; from 6.2 before 6.2.8; 6.3-rc1, 6.3-rc2 — fixed in 5.15.104, 6.1.21, 6.2.8
Linux: 4.4 — fixed in 6.3

How to fix

Upgrade to a fixed version: Linux kernel 5.15.104, 6.1.21, 6.2.8; Linux 6.3. Check the vendor advisory for mitigations.

References

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