CVE-2024-42161: bpf: Avoid uninitialized value in BPF_CORE_READ_BITFIELD

Severity: medium (CVSS 6.3 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: 2024-07-30 · updated 2026-06-17
Weakness: CWE-908

Description

In the Linux kernel, the following vulnerability has been resolved: bpf: Avoid uninitialized value in BPF_CORE_READ_BITFIELD [Changes from V1: - Use a default branch in the switch statement to initialize `val'.] GCC warns that `val' may be used uninitialized in the BPF_CRE_READ_BITFIELD macro, defined in bpf_core_read.h as: [...] unsigned long long val; \ [...] \ switch (__CORE_RELO(s, field, BYTE_SIZE)) { \ case 1: val = *(const unsigned char *)p; break; \ case 2: val = *(const unsigned short *)p; break; \ case 4: val = *(const unsigned int *)p; break; \ case 8: val = *(const unsigned long long *)p; break; \ } \ [...] val; \ } \ This patch adds a default entry in the switch statement that sets `val' to zero in order to avoid the warning, and random values to be used in case __builtin_preserve_field_info returns unexpected values for BPF_FIELD_BYTE_SIZE. Tested in bpf-next master. No regressions.

Affected products

Linux kernel: before 5.10.222; from 5.11 before 5.15.163; from 5.16 before 6.1.98; from 6.2 before 6.6.39; from 6.7 before 6.9.9 — fixed in 5.10.222, 5.15.163, 6.1.98, 6.6.39, 6.9.9

How to fix

Upgrade to a fixed version: Linux kernel 5.10.222, 5.15.163, 6.1.98, 6.6.39. Check the vendor advisory for mitigations.

References

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