linux-cve-announce - CVE-2025-40169: bpf: Reject negative offsets for ALU ops

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Message-ID: <2025111259-CVE-2025-40169-c29b@gregkh>
Date: Wed, 12 Nov 2025 05:46:56 -0500
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-40169: bpf: Reject negative offsets for ALU ops

From: Greg Kroah-Hartman <gregkh@...nel.org>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

bpf: Reject negative offsets for ALU ops

When verifying BPF programs, the check_alu_op() function validates
instructions with ALU operations. The 'offset' field in these
instructions is a signed 16-bit integer.

The existing check 'insn->off > 1' was intended to ensure the offset is
either 0, or 1 for BPF_MOD/BPF_DIV. However, because 'insn->off' is
signed, this check incorrectly accepts all negative values (e.g., -1).

This commit tightens the validation by changing the condition to
'(insn->off != 0 && insn->off != 1)'. This ensures that any value
other than the explicitly permitted 0 and 1 is rejected, hardening the
verifier against malformed BPF programs.

The Linux kernel CVE team has assigned CVE-2025-40169 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 6.6 with commit ec0e2da95f72d4a46050a4d994e4fe471474fd80 and fixed in 6.6.112 with commit 3bce44b344040e5eef3d64d38b157c15304c0aab
	Issue introduced in 6.6 with commit ec0e2da95f72d4a46050a4d994e4fe471474fd80 and fixed in 6.12.53 with commit 5017c302ca4b2a45149ad64e058fa2d5623c068f
	Issue introduced in 6.6 with commit ec0e2da95f72d4a46050a4d994e4fe471474fd80 and fixed in 6.17.3 with commit 21167bf70dbe400563e189ac632258d35eda38b5
	Issue introduced in 6.6 with commit ec0e2da95f72d4a46050a4d994e4fe471474fd80 and fixed in 6.18-rc1 with commit 55c0ced59fe17dee34e9dfd5f7be63cbab207758

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2025-40169
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	kernel/bpf/verifier.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/3bce44b344040e5eef3d64d38b157c15304c0aab
	https://git.kernel.org/stable/c/5017c302ca4b2a45149ad64e058fa2d5623c068f
	https://git.kernel.org/stable/c/21167bf70dbe400563e189ac632258d35eda38b5
	https://git.kernel.org/stable/c/55c0ced59fe17dee34e9dfd5f7be63cbab207758