CVE-2022-48989 Information

Description

In the Linux kernel the following vulnerability has been resolved:

fscache: Fix oops due to race with cookie_lru and use_cookie

If a cookie expires from the LRU and the LRU_DISCARD flag is set but the state machine has not run yet it’s possible another thread can call fscache_use_cookie and begin to use it.

When the cookie_worker finally runs it will see the LRU_DISCARD flag set transition the cookie->state to LRU_DISCARDING which will then withdraw the cookie. Once the cookie is withdrawn the object is removed the below oops will occur because the object associated with the cookie is now NULL.

Fix the oops by clearing the LRU_DISCARD bit if another thread uses the cookie before the cookie_worker runs.

BUG: kernel NULL pointer dereference address: 0000000000000008 … CPU: 31 PID: 44773 Comm: kworker/u130:1 Tainted: G E 6.0.0-5.dneg.x86_64 1 Hardware name: Google Compute Engine/Google Compute Engine BIOS Google 08/26/2022 Workqueue: events_unbound netfs_rreq_write_to_cache_work [netfs] RIP: 0010:cachefiles_prepare_write+0x28/0x90 [cachefiles] … Call Trace: netfs_rreq_write_to_cache_work+0x11c/0x320 [netfs] process_one_work+0x217/0x3e0 worker_thread+0x4a/0x3b0 kthread+0xd6/0x100

CVSS Vector

CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H

Reference

https://git.kernel.org/stable/c/37f0b459c9b67e14fe4dcc3a15d286c4436ed01d https://git.kernel.org/stable/c/b5b52de3214a29911f949459a79f6640969b5487

Attack Complexity

HIGH

Privileges Required

LOW

User Interaction Required

LOW

Scope

NONE

Confidentiality Impact

UNCHANGED

Integrity Impact

NONE

Availability Impact

NONE

Base Score

HIGH

Base Severity

4.7