CVE-2024-58237

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 cant be freplaced with tailcall_freplace.c:entry_freplace() that does a tail call.

Affected Software

References

• https://git.kernel.org/stable/c/1a4607ffba35bf2a630aab299e34dd3f6e658d70
• https://git.kernel.org/stable/c/1c2244437f9ad3dd91215f920401a14f2542dbfc