Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx> wrote:
> On Thu, Apr 20, 2023 at 02:44:55PM +0200, Florian Westphal wrote:
> > +
> > +SEC("netfilter")
> > +__description("netfilter valid context access")
> > +__success __failure_unpriv
> > +__retval(1)
> > +__naked void with_invalid_ctx_access_test5(void)
> > +{
> > + asm volatile (" \
> > + r2 = *(u64*)(r1 + %[__bpf_nf_ctx_state]); \
> > + r1 = *(u64*)(r1 + %[__bpf_nf_ctx_skb]); \
> > + r0 = 1; \
> > + exit; \
> > +" :
> > + : __imm_const(__bpf_nf_ctx_state, offsetof(struct bpf_nf_ctx, state)),
> > + __imm_const(__bpf_nf_ctx_skb, offsetof(struct bpf_nf_ctx, skb))
> > + : __clobber_all);
>
> Could you write this one in C instead?
>
> Also check that skb and state are dereferenceable after that.
My bad. Added this and that:
SEC("netfilter")
__description("netfilter valid context read and invalid write")
__failure __msg("only read is supported")
int with_invalid_ctx_access_test5(struct bpf_nf_ctx *ctx)
{
struct nf_hook_state *state = (void *)ctx->state;
state->sk = NULL;
return 1;
}
SEC("netfilter")
__description("netfilter test prog with skb and state read access")
__success __failure_unpriv
__retval(0)
int with_valid_ctx_access_test6(struct bpf_nf_ctx *ctx)
{
const struct nf_hook_state *state = ctx->state;
struct sk_buff *skb = ctx->skb;
const struct iphdr *iph;
const struct tcphdr *th;
u8 buffer_iph[20] = {};
u8 buffer_th[40] = {};
struct bpf_dynptr ptr;
uint8_t ihl;
if (skb->len <= 20 || bpf_dynptr_from_skb(skb, 0, &ptr))
return 1;
iph = bpf_dynptr_slice(&ptr, 0, buffer_iph, sizeof(buffer_iph));
if (!iph)
return 1;
if (state->pf != 2)
return 1;
ihl = iph->ihl << 2;
th = bpf_dynptr_slice(&ptr, ihl, buffer_th, sizeof(buffer_th));
if (!th)
return 1;
return th->dest == bpf_htons(22) ? 1 : 0;
}
"Worksforme". Is there anything else thats missing?
If not I'll send v5 on Monday.
> Since they should be seen as trusted ptr_to_btf_id skb->len and state->sk should work.
> You cannot craft this test case in asm, since it needs CO-RE.
>
> Also see that BPF CI is not happy:
> https://github.com/kernel-patches/bpf/actions/runs/4757642030/jobs/8455500277
> Error: #112 libbpf_probe_prog_types
> Error: #112/32 libbpf_probe_prog_types/BPF_PROG_TYPE_NETFILTER
> Error: #113 libbpf_str
> Error: #113/4 libbpf_str/bpf_prog_type_str
prog_type_name[] lacks "netfilter" entry, and a missing 'case
PROG_NETFILTER', v5 should pass this now.
