CVE-2024-26884: bpf: Fix hashtab overflow check on 32-bit arches

Severity: high (CVSS 7.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2024-04-17 · updated 2026-10-15
Weakness: CWE-119

Description

In the Linux kernel, the following vulnerability has been resolved: bpf: Fix hashtab overflow check on 32-bit arches The hashtab code relies on roundup_pow_of_two() to compute the number of hash buckets, and contains an overflow check by checking if the resulting value is 0. However, on 32-bit arches, the roundup code itself can overflow by doing a 32-bit left-shift of an unsigned long value, which is undefined behaviour, so it is not guaranteed to truncate neatly. This was triggered by syzbot on the DEVMAP_HASH type, which contains the same check, copied from the hashtab code. So apply the same fix to hashtab, by moving the overflow check to before the roundup.

Affected products

Linux kernel: from 3.19 before 4.19.311; from 4.20 before 5.4.273; from 5.5 before 5.10.214; from 5.11 before 5.15.153; from 5.16 before 6.1.83; from 6.2 before 6.6.23 — fixed in 4.19.311, 5.10.214, 5.15.153, 5.4.273, 6.1.83, 6.6.23

How to fix

Upgrade to a fixed version: Linux kernel 4.19.311, 5.10.214, 5.15.153, 5.4.273. Check the vendor advisory for mitigations.

References

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