CVE-2024-58237: bpf: consider that tail calls invalidate packet pointers

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

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

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

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

bpf: consider that tail calls invalidate packet pointers

Tail-called programs could execute any of the helpers that invalidate
packet pointers. Hence, conservatively assume that each tail call
invalidates packet pointers.

Making the change in bpf_helper_changes_pkt_data() automatically makes
use of check_cfg() logic that computes 'changes_pkt_data' effect for
global sub-programs, such that the following program could be
rejected:

    int tail_call(struct __sk_buff *sk)
    {
    	bpf_tail_call_static(sk, &jmp_table, 0);
    	return 0;
    }

    SEC("tc")
    int not_safe(struct __sk_buff *sk)
    {
    	int *p = (void *)(long)sk->data;
    	... make p valid ...
    	tail_call(sk);
    	*p = 42; /* this is unsafe */
    	...
    }

The tc_bpf2bpf.c:subprog_tc() needs change: mark it as a function that
can invalidate packet pointers. Otherwise, it can't be freplaced with
tailcall_freplace.c:entry_freplace() that does a tail call.

The Linux kernel CVE team has assigned CVE-2024-58237 to this issue.


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

	Issue introduced in 5.6 with commit 51c39bb1d5d105a02e29aa7960f0a395086e6342 and fixed in 6.12.9 with commit 1c2244437f9ad3dd91215f920401a14f2542dbfc
	Issue introduced in 5.6 with commit 51c39bb1d5d105a02e29aa7960f0a395086e6342 and fixed in 6.13 with commit 1a4607ffba35bf2a630aab299e34dd3f6e658d70

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-2024-58237
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
	tools/testing/selftests/bpf/progs/tc_bpf2bpf.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/1c2244437f9ad3dd91215f920401a14f2542dbfc
	https://git.kernel.org/stable/c/1a4607ffba35bf2a630aab299e34dd3f6e658d70