Bug 2460672 (CVE-2026-31525) - CVE-2026-31525 kernel: bpf: Fix undefined behavior in interpreter sdiv/smod for INT_MIN
Summary: CVE-2026-31525 kernel: bpf: Fix undefined behavior in interpreter sdiv/smod f...
Keywords:
Status: NEW
Alias: CVE-2026-31525
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
medium
medium
Target Milestone: ---
Assignee: Product Security
QA Contact:
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2026-04-22 15:04 UTC by OSIDB Bzimport
Modified: 2026-04-24 15:07 UTC (History)
2 users (show)

Fixed In Version:
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Description OSIDB Bzimport 2026-04-22 15:04:33 UTC
In the Linux kernel, the following vulnerability has been resolved:

bpf: Fix undefined behavior in interpreter sdiv/smod for INT_MIN

The BPF interpreter's signed 32-bit division and modulo handlers use
the kernel abs() macro on s32 operands. The abs() macro documentation
(include/linux/math.h) explicitly states the result is undefined when
the input is the type minimum. When DST contains S32_MIN (0x80000000),
abs((s32)DST) triggers undefined behavior and returns S32_MIN unchanged
on arm64/x86. This value is then sign-extended to u64 as
0xFFFFFFFF80000000, causing do_div() to compute the wrong result.

The verifier's abstract interpretation (scalar32_min_max_sdiv) computes
the mathematically correct result for range tracking, creating a
verifier/interpreter mismatch that can be exploited for out-of-bounds
map value access.

Introduce abs_s32() which handles S32_MIN correctly by casting to u32
before negating, avoiding signed overflow entirely. Replace all 8
abs((s32)...) call sites in the interpreter's sdiv32/smod32 handlers.

s32 is the only affected case -- the s64 division/modulo handlers do
not use abs().


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