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

Vulnerability summary

CVE-2024-42161 is a medium (CVSS 6.3) Use of Uninitialized Resource vulnerability in linux. EPSS estimates a 0.22% chance of exploitation in the next 30 days, higher than 12.6% of scored vulnerabilities.

Timeline

1. 30-07-2024
   PublishedVulnerability first disclosed.
2. 11-05-2026
   Last modifiedVulnerability information updated.

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.

• CWE-908Use of Uninitialized ResourceThe product uses or accesses a resource that has not been initialized.