Subject: CVE-2024-40996: bpf: Avoid splat in pskb_pull_reason

From: Greg Kroah-Hartman <[email-masked]>

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

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

bpf: Avoid splat in pskb_pull_reason

syzkaller builds (CONFIG_DEBUG_NET=y) frequently trigger a debug
hint in pskb_may_pull.

We'd like to retain this debug check because it might hint at integer
overflows and other issues (kernel code should pull headers, not huge
value).

In bpf case, this splat isn't interesting at all: such (nonsensical)
bpf programs are typically generated by a fuzzer anyway.

Do what Eric suggested and suppress such warning.

For CONFIG_DEBUG_NET=n we don't need the extra check because
pskb_may_pull will do the right thing: return an error without the
WARN() backtrace.

The Linux kernel CVE team has assigned CVE-2024-40996 to this issue.

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

	Issue introduced in 6.1.86 with commit 8af60bb2b215 and fixed in 6.1.96 with commit dacc15e9cb24
	Issue introduced in 6.6.27 with commit 1b2b26595bb0 and fixed in 6.6.36 with commit 7f9644782c55
	Issue introduced in 6.9 with commit 219eee9c0d16 and fixed in 6.9.7 with commit 5e90258303a3
	Issue introduced in 6.9 with commit 219eee9c0d16 and fixed in 6.10 with commit 2bbe3e5a2f4e
	Issue introduced in 6.8.6 with commit fff05b2b004d

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-2024-40996
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:
	net/core/filter.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/dacc15e9cb248d19e5fc63c54bef0b9b55007761
	https://git.kernel.org/stable/c/7f9644782c559635bd676c12c59389a34ed7c866
	https://git.kernel.org/stable/c/5e90258303a358e88737afb5048bee9113beea3a
	https://git.kernel.org/stable/c/2bbe3e5a2f4ef69d13be54f1cf895b4658287080