linux-cve-announce - CVE-2024-42072: bpf: Fix may

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Message-ID: <2024072953-CVE-2024-42072-d6af@gregkh>
Date: Mon, 29 Jul 2024 17:53:01 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2024-42072: bpf: Fix may_goto with negative offset.

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

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

bpf: Fix may_goto with negative offset.

Zac's syzbot crafted a bpf prog that exposed two bugs in may_goto.
The 1st bug is the way may_goto is patched. When offset is negative
it should be patched differently.
The 2nd bug is in the verifier:
when current state may_goto_depth is equal to visited state may_goto_depth
it means there is an actual infinite loop. It's not correct to prune
exploration of the program at this point.
Note, that this check doesn't limit the program to only one may_goto insn,
since 2nd and any further may_goto will increment may_goto_depth only
in the queued state pushed for future exploration. The current state
will have may_goto_depth == 0 regardless of number of may_goto insns
and the verifier has to explore the program until bpf_exit.

The Linux kernel CVE team has assigned CVE-2024-42072 to this issue.

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

	Issue introduced in 6.9 with commit 011832b97b31 and fixed in 6.9.8 with commit 175827e04f4b
	Issue introduced in 6.9 with commit 011832b97b31 and fixed in 6.10 with commit 2b2efe1937ca

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-2024-42072
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/175827e04f4be53f3dfb57edf12d0d49b18fd939
	https://git.kernel.org/stable/c/2b2efe1937ca9f8815884bd4dcd5b32733025103