Merge branch 'bpf-fix-abs-int_min-undefined-behavior-in-interpreter-sdiv-smod'

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Jenny Guanni Qu says:

====================
bpf: Fix abs(INT_MIN) undefined behavior in interpreter sdiv/smod

The BPF interpreter's signed 32-bit division and modulo handlers use
abs() on s32 operands, which is undefined for S32_MIN. This causes
the interpreter to compute wrong results, creating a mismatch with
the verifier's range tracking.

For example, INT_MIN / 2 returns 0x40000000 instead of the correct
0xC0000000. The verifier tracks the correct range, so a crafted BPF
program can exploit the mismatch for out-of-bounds map value access
(confirmed by KASAN).

Patch 1 introduces abs_s32() which handles S32_MIN correctly and
replaces all 8 abs((s32)...) call sites. s32 is the only affected
case -- the s64 handlers do not use abs().

Patch 2 adds selftests covering sdiv32 and smod32 with INT_MIN
dividend to prevent regression.

Changes since v4:
  - Renamed __safe_abs32() to abs_s32() and dropped inline keyword
    per Alexei Starovoitov's feedback

Changes since v3:
  - Fixed stray blank line deletion in the file header
  - Improved comment per Yonghong Song's suggestion
  - Added JIT vs interpreter context to selftest commit message

Changes since v2:
  - Simplified to use -(u32)x per Mykyta Yatsenko's suggestion

Changes since v1:
  - Moved helper above kerneldoc comment block to fix build warnings
====================

Link: https://patch.msgid.link/20260311011116.2108005-1-qguanni@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

...

This commit is contained in:

Alexei Starovoitov 2026-03-21 13:12:17 -07:00

parent a1e5c46eae 4ac95c65ef

commit 1abd3feb36

2 changed files with 72 additions and 8 deletions

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22

kernel/bpf/core.c

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58

tools/testing/selftests/bpf/progs/verifier_sdiv.c

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