linux-cve-announce - CVE-2025-40050: bpf: Skip scalar adjustment for BPF

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Message-ID: <2025102814-CVE-2025-40050-1f2d@gregkh>
Date: Tue, 28 Oct 2025 12:48:27 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-40050: bpf: Skip scalar adjustment for BPF_NEG if dst is a pointer

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

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

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

bpf: Skip scalar adjustment for BPF_NEG if dst is a pointer

In check_alu_op(), the verifier currently calls check_reg_arg() and
adjust_scalar_min_max_vals() unconditionally for BPF_NEG operations.
However, if the destination register holds a pointer, these scalar
adjustments are unnecessary and potentially incorrect.

This patch adds a check to skip the adjustment logic when the destination
register contains a pointer.

The Linux kernel CVE team has assigned CVE-2025-40050 to this issue.


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

	Issue introduced in 6.17 with commit aced132599b3c8884c050218d4c48eef203678f6 and fixed in 6.17.3 with commit b9ef4963227246b9222e1559ddeec8e7af63e6c6
	Issue introduced in 6.17 with commit aced132599b3c8884c050218d4c48eef203678f6 and fixed in 6.18-rc1 with commit 34904582b502a86fdb4d7984b12cacd2faabbe0d

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-2025-40050
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/b9ef4963227246b9222e1559ddeec8e7af63e6c6
	https://git.kernel.org/stable/c/34904582b502a86fdb4d7984b12cacd2faabbe0d