CVE-2026-31525

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> bpf: Fix undefined behavior in interpreter sdiv/smod for INT_MIN<br /> <br /> The BPF interpreter&amp;#39;s signed 32-bit division and modulo handlers use<br /> the kernel abs() macro on s32 operands. The abs() macro documentation<br /> (include/linux/math.h) explicitly states the result is undefined when<br /> the input is the type minimum. When DST contains S32_MIN (0x80000000),<br /> abs((s32)DST) triggers undefined behavior and returns S32_MIN unchanged<br /> on arm64/x86. This value is then sign-extended to u64 as<br /> 0xFFFFFFFF80000000, causing do_div() to compute the wrong result.<br /> <br /> The verifier&amp;#39;s abstract interpretation (scalar32_min_max_sdiv) computes<br /> the mathematically correct result for range tracking, creating a<br /> verifier/interpreter mismatch that can be exploited for out-of-bounds<br /> map value access.<br /> <br /> Introduce abs_s32() which handles S32_MIN correctly by casting to u32<br /> before negating, avoiding signed overflow entirely. Replace all 8<br /> abs((s32)...) call sites in the interpreter&amp;#39;s sdiv32/smod32 handlers.<br /> <br /> s32 is the only affected case -- the s64 division/modulo handlers do<br /> not use abs().