CVE-2024-58237 Information

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(	c\)
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.

Reference

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