On Wed, Jan 10, 2024 at 1:53 PM Hao Sun <sunhao.th@xxxxxxxxx> wrote:
>
> Add two cases for PTR_TO_FLOW_KEYS alu. One for rejecting alu with
> variable offset, another for fixed offset.
>
> Signed-off-by: Hao Sun <sunhao.th@xxxxxxxxx>
> ---
> .../bpf/progs/verifier_value_illegal_alu.c | 37 +++++++++++++++++++
> 1 file changed, 37 insertions(+)
>
> diff --git a/tools/testing/selftests/bpf/progs/verifier_value_illegal_alu.c b/tools/testing/selftests/bpf/progs/verifier_value_illegal_alu.c
> index 71814a753216..49089361c98a 100644
> --- a/tools/testing/selftests/bpf/progs/verifier_value_illegal_alu.c
> +++ b/tools/testing/selftests/bpf/progs/verifier_value_illegal_alu.c
> @@ -146,4 +146,41 @@ l0_%=: exit; \
> : __clobber_all);
> }
>
> +SEC("flow_dissector")
> +__description("flow_keys illegal alu op with variable offset")
> +__failure
> +__msg("R7 pointer arithmetic on flow_keys prohibited")
> +__naked void flow_keys_illegal_variable_offset_alu(void)
> +{
> + asm volatile(" \
> + r6 = r1; \
> + r7 = *(u64*)(r6 + %[flow_keys_off]); \
> + r8 = 8; \
> + r8 /= 1; \
> + r8 &= 8; \
> + r7 += r8; \
> + r0 = *(u64*)(r7 + 0); \
> + exit; \
> +" :
> + : __imm_const(flow_keys_off, offsetof(struct __sk_buff, flow_keys))
> + : __clobber_all);
> +}
> +
> +SEC("flow_dissector")
> +__description("flow_keys valid alu op with fixed offset")
> +__success
> +__naked void flow_keys_legal_fixed_offset_alu(void)
> +{
> + asm volatile(" \
> + r6 = r1; \
> + r7 = *(u64*)(r6 + %[flow_keys_off]); \
> + r8 = 8; \
> + r7 += r8; \
> + r0 = *(u64*)(r7 + 0); \
> + exit; \
> +" :
> + : __imm_const(flow_keys_off, offsetof(struct __sk_buff, flow_keys))
> + : __clobber_all);
> +}
> +
The format here is strange and should be fixed later.
I'm also curious, why only fixed-off is used in check_flow_keys_access()
for validation?
