2024-01-12 15:21:08

by Hao Sun

Subject: [PATCH v3 2/2] selftests/bpf: Add tests for alu on PTR_TO_FLOW_KEYS

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 <[email protected]>
---
.../bpf/progs/verifier_value_illegal_alu.c | 36 +++++++++++++++++++
1 file changed, 36 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..3bcccb4cbc85 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 +146,40 @@ 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);
+}
+
char _license[] SEC("license") = "GPL";
--
2.34.1

2024-01-12 18:14:53

by Yonghong Song

Subject: Re: [PATCH v3 2/2] selftests/bpf: Add tests for alu on PTR_TO_FLOW_KEYS

On 1/12/24 7:20 AM, Hao Sun 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 <[email protected]>
> ---
> .../bpf/progs/verifier_value_illegal_alu.c | 36 +++++++++++++++++++
> 1 file changed, 36 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..3bcccb4cbc85 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 +146,40 @@ 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);
> +}

Please remove the above '__success' case from this file. This file,
verifier_value_illegal_alu.c, only contains failure cases.

For the fixed offset, we already have C code to verify,
e.g., in bpf_flow.c.