[PATCH bpf v2 02/11] selftests/bpf: Test dynptr slices past end of skb

[Emil Tsalapatis <emil@etsalapatis.com>]

Add a selftest to ensure dynptr slices cannot include
past the end of the linear area of an skb.

Signed-off-by: Emil Tsalapatis <emil@etsalapatis.com>
---
 .../testing/selftests/bpf/prog_tests/dynptr.c | 10 ++++++++++
 .../selftests/bpf/progs/dynptr_success.c      | 20 +++++++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/dynptr.c b/tools/testing/selftests/bpf/prog_tests/dynptr.c
index 5fda11590..439656036 100644
--- a/tools/testing/selftests/bpf/prog_tests/dynptr.c
+++ b/tools/testing/selftests/bpf/prog_tests/dynptr.c
@@ -9,6 +9,7 @@
 enum test_setup_type {
 	SETUP_SYSCALL_SLEEP,
 	SETUP_SKB_PROG,
+	SETUP_SKB_PROG_NONLINEAR,
 	SETUP_SKB_PROG_TP,
 	SETUP_XDP_PROG,
 };
@@ -32,6 +33,7 @@ static struct {
 	{"test_ringbuf", SETUP_SYSCALL_SLEEP},
 	{"test_skb_readonly", SETUP_SKB_PROG},
 	{"test_dynptr_skb_data", SETUP_SKB_PROG},
+	{"test_dynptr_skb_slice_non_linear", SETUP_SKB_PROG_NONLINEAR},
 	{"test_dynptr_skb_meta_data", SETUP_SKB_PROG},
 	{"test_dynptr_skb_meta_flags", SETUP_SKB_PROG},
 	{"test_adjust", SETUP_SYSCALL_SLEEP},
@@ -94,7 +96,9 @@ static void verify_success(const char *prog_name, enum test_setup_type setup_typ
 		bpf_link__destroy(link);
 		break;
 	case SETUP_SKB_PROG:
+	case SETUP_SKB_PROG_NONLINEAR:
 	{
+		struct __sk_buff ctx = {};
 		int prog_fd;
 		char buf[64];
 
@@ -106,6 +110,12 @@ static void verify_success(const char *prog_name, enum test_setup_type setup_typ
 			    .repeat = 1,
 		);
 
+		if (setup_type == SETUP_SKB_PROG_NONLINEAR) {
+			ctx.data_end = ETH_HLEN + sizeof(struct iphdr);
+			topts.ctx_in = &ctx;
+			topts.ctx_size_in = sizeof(ctx);
+		}
+
 		prog_fd = bpf_program__fd(prog);
 		if (!ASSERT_GE(prog_fd, 0, "prog_fd"))
 			goto cleanup;
diff --git a/tools/testing/selftests/bpf/progs/dynptr_success.c b/tools/testing/selftests/bpf/progs/dynptr_success.c
index e0745b6e4..b668ebd61 100644
--- a/tools/testing/selftests/bpf/progs/dynptr_success.c
+++ b/tools/testing/selftests/bpf/progs/dynptr_success.c
@@ -10,6 +10,7 @@
 #include "errno.h"
 
 #define PAGE_SIZE_64K 65536
+#define TEST_SKB_LINEAR_SIZE (sizeof(struct ethhdr) + sizeof(struct iphdr))
 
 char _license[] SEC("license") = "GPL";
 
@@ -211,6 +212,25 @@ int test_dynptr_skb_data(struct __sk_buff *skb)
 	return 1;
 }
 
+SEC("?tc")
+int test_dynptr_skb_slice_non_linear(struct __sk_buff *skb)
+{
+	struct bpf_dynptr ptr;
+	void *data;
+
+	if (bpf_dynptr_from_skb(skb, 0, &ptr)) {
+		err = 1;
+		return 1;
+	}
+
+	/* Ensure we cannot read past the end of the buffer. */
+	data = bpf_dynptr_slice(&ptr, TEST_SKB_LINEAR_SIZE + 1, NULL, 1);
+	if (data)
+		err = 2;
+
+	return 1;
+}
+
 SEC("?tc")
 int test_dynptr_skb_meta_data(struct __sk_buff *skb)
 {
-- 
2.54.0