Subject: CVE-2024-38574: libbpf: Prevent null-pointer dereference when prog to load has no BTF

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

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

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

libbpf: Prevent null-pointer dereference when prog to load has no BTF

In bpf_objec_load_prog(), there's no guarantee that obj->btf is non-NULL
when passing it to btf__fd(), and this function does not perform any
check before dereferencing its argument (as bpf_object__btf_fd() used to
do). As a consequence, we get segmentation fault errors in bpftool (for
example) when trying to load programs that come without BTF information.

v2: Keep btf__fd() in the fix instead of reverting to bpf_object__btf_fd().

The Linux kernel CVE team has assigned CVE-2024-38574 to this issue.

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

	Issue introduced in 6.8 with commit df7c3f7d3a3d and fixed in 6.8.12 with commit ef80b59acfa4
	Issue introduced in 6.8 with commit df7c3f7d3a3d and fixed in 6.9.3 with commit 1fd91360a758
	Issue introduced in 6.8 with commit df7c3f7d3a3d and fixed in 6.10 with commit 9bf48fa19a4b

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-2024-38574
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:
	tools/lib/bpf/libbpf.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/ef80b59acfa4dee4b5eaccb15572b69248831104
	https://git.kernel.org/stable/c/1fd91360a75833b7110af9834ae26c977e1273e0
	https://git.kernel.org/stable/c/9bf48fa19a4b1d186e08b20bf7e5de26a15644fb