CVE-2026-98049
🔶 mediumSummary
In the Linux kernel, the following vulnerability has been resolved: bpf: zero extend the result of an arena 32-bit cmpxchg bpf_convert_ctx_accesses() rewrites an atomic on an arena pointer from BPF_STX | BPF_ATOMIC to BPF_STX | BPF_PROBE_ATOMIC, and it runs before bpf_opt_subreg_zext_lo32_rnd_hi32(). That pass emits an explicit zero extension for a 32-bit cmpxchg even when bpf_jit_needs_zext() is false. This is done because on some architectures 32-bit cmpxchg requires explicit zero extension
Description
In the Linux kernel, the following vulnerability has been resolved:
bpf: zero extend the result of an arena 32-bit cmpxchg
bpf_convert_ctx_accesses() rewrites an atomic on an arena pointer from
BPF_STX | BPF_ATOMIC to BPF_STX | BPF_PROBE_ATOMIC, and it runs before
bpf_opt_subreg_zext_lo32_rnd_hi32().
That pass emits an explicit zero extension for a 32-bit cmpxchg even
when bpf_jit_needs_zext() is false. This is done because on some
architectures 32-bit cmpxchg requires explicit zero extension for the
dst register. E.g. on x86-64 'lock cmpxchg' does not change the %eax
if comparison is successful, while BPF semantics declare that each
operation on a 32-bit register zero extends it's upper half.
is_cmpxchg_insn() matches BPF_MODE == BPF_ATOMIC only, so an arena
cmpxchg misses said zero extension adjustment. This patch adjusts
is_cmpxchg_insn() to match BPF_PROBE_ATOMIC alongside BPF_ATOMIC.
📊 Relative Risk Intelligence
This CVE is Lower Risk - more severe than 31.3% of all 365,863 vulnerabilities in our database.
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H