CVE-2024-39482: bcache: fix variable length array abuse in btree_iter

Severity: medium (CVSS 5.5 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: 2024-07-05 · updated 2026-10-15
Weakness: CWE-770

Description

In the Linux kernel, the following vulnerability has been resolved: bcache: fix variable length array abuse in btree_iter btree_iter is used in two ways: either allocated on the stack with a fixed size MAX_BSETS, or from a mempool with a dynamic size based on the specific cache set. Previously, the struct had a fixed-length array of size MAX_BSETS which was indexed out-of-bounds for the dynamically-sized iterators, which causes UBSAN to complain. This patch uses the same approach as in bcachefs's sort_iter and splits the iterator into a btree_iter with a flexible array member and a btree_iter_stack which embeds a btree_iter as well as a fixed-length data array.

Affected products

Linux kernel: from 5.10 before 5.10.221; from 5.15 before 5.15.162; from 6.1 before 6.1.94; from 6.6 before 6.6.34; from 6.9 before 6.9.5 — fixed in 5.10.221, 5.15.162, 6.1.94, 6.6.34, 6.9.5

How to fix

Upgrade to a fixed version: Linux kernel 5.10.221, 5.15.162, 6.1.94, 6.6.34. Check the vendor advisory for mitigations.

References

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