selftests/bpf: Add tests for ldsx of pkt data/data_end/data_meta accesses

The following tests are added to verifier_ldsx.c:
  - sign extension of data/data_end/data_meta for tcx programs.
    The actual checking is in bpf_skb_is_valid_access() which
    is called by sk_filter, cg_skb, lwt, tc(tcx) and sk_skb.
  - sign extension of data/data_end/data_meta for xdp programs.
  - sign extension of data/data_end for flow_dissector programs.

All newly-added tests have verification failure with message
"invalid bpf_context access". Without previous patch, all these
tests succeeded verification.
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20240723153444.2430365-1-yonghong.song@linux.devSigned-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>

tools/testing/selftests/bpf/progs/verifier_ldsx.c

@@ -144,6 +144,118 @@ __naked void ldsx_s32_range(void)
 	: __clobber_all);
 }
 
+SEC("xdp")
+__description("LDSX, xdp s32 xdp_md->data")
+__failure __msg("invalid bpf_context access")
+__naked void ldsx_ctx_1(void)
+{
+	asm volatile (
+	"r2 = *(s32 *)(r1 + %[xdp_md_data]);"
+	"r0 = 0;"
+	"exit;"
+	:
+	: __imm_const(xdp_md_data, offsetof(struct xdp_md, data))
+	: __clobber_all);
+}
+
+SEC("xdp")
+__description("LDSX, xdp s32 xdp_md->data_end")
+__failure __msg("invalid bpf_context access")
+__naked void ldsx_ctx_2(void)
+{
+	asm volatile (
+	"r2 = *(s32 *)(r1 + %[xdp_md_data_end]);"
+	"r0 = 0;"
+	"exit;"
+	:
+	: __imm_const(xdp_md_data_end, offsetof(struct xdp_md, data_end))
+	: __clobber_all);
+}
+
+SEC("xdp")
+__description("LDSX, xdp s32 xdp_md->data_meta")
+__failure __msg("invalid bpf_context access")
+__naked void ldsx_ctx_3(void)
+{
+	asm volatile (
+	"r2 = *(s32 *)(r1 + %[xdp_md_data_meta]);"
+	"r0 = 0;"
+	"exit;"
+	:
+	: __imm_const(xdp_md_data_meta, offsetof(struct xdp_md, data_meta))
+	: __clobber_all);
+}
+
+SEC("tcx/ingress")
+__description("LDSX, tcx s32 __sk_buff->data")
+__failure __msg("invalid bpf_context access")
+__naked void ldsx_ctx_4(void)
+{
+	asm volatile (
+	"r2 = *(s32 *)(r1 + %[sk_buff_data]);"
+	"r0 = 0;"
+	"exit;"
+	:
+	: __imm_const(sk_buff_data, offsetof(struct __sk_buff, data))
+	: __clobber_all);
+}
+
+SEC("tcx/ingress")
+__description("LDSX, tcx s32 __sk_buff->data_end")
+__failure __msg("invalid bpf_context access")
+__naked void ldsx_ctx_5(void)
+{
+	asm volatile (
+	"r2 = *(s32 *)(r1 + %[sk_buff_data_end]);"
+	"r0 = 0;"
+	"exit;"
+	:
+	: __imm_const(sk_buff_data_end, offsetof(struct __sk_buff, data_end))
+	: __clobber_all);
+}
+
+SEC("tcx/ingress")
+__description("LDSX, tcx s32 __sk_buff->data_meta")
+__failure __msg("invalid bpf_context access")
+__naked void ldsx_ctx_6(void)
+{
+	asm volatile (
+	"r2 = *(s32 *)(r1 + %[sk_buff_data_meta]);"
+	"r0 = 0;"
+	"exit;"
+	:
+	: __imm_const(sk_buff_data_meta, offsetof(struct __sk_buff, data_meta))
+	: __clobber_all);
+}
+
+SEC("flow_dissector")
+__description("LDSX, flow_dissector s32 __sk_buff->data")
+__failure __msg("invalid bpf_context access")
+__naked void ldsx_ctx_7(void)
+{
+	asm volatile (
+	"r2 = *(s32 *)(r1 + %[sk_buff_data]);"
+	"r0 = 0;"
+	"exit;"
+	:
+	: __imm_const(sk_buff_data, offsetof(struct __sk_buff, data))
+	: __clobber_all);
+}
+
+SEC("flow_dissector")
+__description("LDSX, flow_dissector s32 __sk_buff->data_end")
+__failure __msg("invalid bpf_context access")
+__naked void ldsx_ctx_8(void)
+{
+	asm volatile (
+	"r2 = *(s32 *)(r1 + %[sk_buff_data_end]);"
+	"r0 = 0;"
+	"exit;"
+	:
+	: __imm_const(sk_buff_data_end, offsetof(struct __sk_buff, data_end))
+	: __clobber_all);
+}
+
 #else
 
 SEC("socket")