Subject: CVE-2024-47728: bpf: Zero former ARG_PTR_TO_{LONG,INT} args in case of error

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

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

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

bpf: Zero former ARG_PTR_TO_{LONG,INT} args in case of error

For all non-tracing helpers which formerly had ARG_PTR_TO_{LONG,INT} as input
arguments, zero the value for the case of an error as otherwise it could leak
memory. For tracing, it is not needed given CAP_PERFMON can already read all
kernel memory anyway hence bpf_get_func_arg() and bpf_get_func_ret() is skipped
in here.

Also, the MTU helpers mtu_len pointer value is being written but also read.
Technically, the MEM_UNINIT should not be there in order to always force init.
Removing MEM_UNINIT needs more verifier rework though: MEM_UNINIT right now
implies two things actually: i) write into memory, ii) memory does not have
to be initialized. If we lift MEM_UNINIT, it then becomes: i) read into memory,
ii) memory must be initialized. This means that for bpf_*_check_mtu() we're
readding the issue we're trying to fix, that is, it would then be able to
write back into things like .rodata BPF maps. Follow-up work will rework the
MEM_UNINIT semantics such that the intent can be better expressed. For now
just clear the *mtu_len on error path which can be lifted later again.

The Linux kernel CVE team has assigned CVE-2024-47728 to this issue.

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

	Issue introduced in 5.2 with commit d7a4cb9b6705 and fixed in 6.1.113 with commit 8397bf78988f
	Issue introduced in 5.2 with commit d7a4cb9b6705 and fixed in 6.6.54 with commit a634fa8e480a
	Issue introduced in 5.2 with commit d7a4cb9b6705 and fixed in 6.10.13 with commit 599d15b6d033
	Issue introduced in 5.2 with commit d7a4cb9b6705 and fixed in 6.11.2 with commit 594a9f5a8d2d
	Issue introduced in 5.2 with commit d7a4cb9b6705 and fixed in 6.12-rc1 with commit 4b3786a6c539

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-2024-47728
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/helpers.c
	kernel/bpf/syscall.c
	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/8397bf78988f3ae9dbebb0200189a62a57264980
	https://git.kernel.org/stable/c/a634fa8e480ac2423f86311a602f6295df2c8ed0
	https://git.kernel.org/stable/c/599d15b6d03356a97bff7a76155c5604c42a2962
	https://git.kernel.org/stable/c/594a9f5a8d2de2573a856e506f77ba7dd2cefc6a
	https://git.kernel.org/stable/c/4b3786a6c5397dc220b1483d8e2f4867743e966f