[PATCH bpf v2 02/11] selftests/bpf: Test dynptr slices past end of skb
From: Emil Tsalapatis <emil@etsalapatis.com>
Date: 2026-09-22 17:20:42
Also in:
bpf
Subsystem:
bpf [general] (safe dynamic programs and tools), bpf [selftests] (test runners & infrastructure), kernel selftest framework, the rest · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Shuah Khan, Shuah Khan, Linus Torvalds
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