PT-2021-8278 · Linux+2 · Linux Kernel+2
Ali Saidi
·
Published
2021-04-15
·
Updated
2024-08-19
·
CVE-2021-46921
CVSS v3.1
5.5
Medium
| Vector | AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N |
Name of the Vulnerable Software and Affected Versions
Linux kernel (affected versions not specified)
Description
The issue is related to the locking mechanism in the Linux kernel, specifically in the queued write lock slowpath() function. A reader can acquire the lock without holding the wait lock, allowing reads to observe values speculatively before the write lock is truly acquired. This exposes a window to an A-B-A problem, where a value change can be seen by the writer before the reader unlocks. The problem has been observed in epoll, where the reader does a xchg while holding the read lock, but the writer can see a value change out from under it. The
atomic cond read acquire() and atomic cmpxchg relaxed() functions are involved in this issue. Switching the cmpxchg to use acquire semantics addresses this issue.Recommendations
At the moment, there is no information about a newer version that contains a fix for this vulnerability.
Exposure of Resource to Wrong Sphere
Found an issue in the description? Have something to add? Feel free to write us 👾
Weakness Enumeration
Related Identifiers
Affected Products
Astra Linux
Linux Kernel
Suse