[bpf-next,v3,3/5] selftests/bpf: Check overflow in optional buffer

Commit Message

Daniel Rosenberg May 6, 2023, 1:31 a.m. UTC

This ensures we still reject invalid memory accesses in buffers that are
marked optional.

Signed-off-by: Daniel Rosenberg <[e-mail]>
---
 .../testing/selftests/bpf/progs/dynptr_fail.c | 20 +++++++++++++++++++
 1 file changed, 20 insertions(+)

Patch

diff --git a/tools/testing/selftests/bpf/progs/dynptr_fail.c b/tools/testing/selftests/bpf/progs/dynptr_fail.c
index efe4ce72d00e..c2f0e18af951 100644
--- a/tools/testing/selftests/bpf/progs/dynptr_fail.c
+++ b/tools/testing/selftests/bpf/progs/dynptr_fail.c
@@ -1665,3 +1665,23 @@  int clone_xdp_packet_data(struct xdp_md *xdp)
 
 	return 0;
 }
+
+/* Buffers that are provided must be sufficiently long */
+SEC("?cgroup_skb/egress")
+__failure __msg("memory, len pair leads to invalid memory access")
+int test_dynptr_skb_small_buff(struct __sk_buff *skb)
+{
+	struct bpf_dynptr ptr;
+	char buffer[8] = {};
+	__u64 *data;
+
+	if (bpf_dynptr_from_skb(skb, 0, &ptr)) {
+		err = 1;
+		return 1;
+	}
+
+	/* This may return NULL. SKB may require a buffer */
+	data = bpf_dynptr_slice(&ptr, 0, buffer, 9);
+
+	return !!data;
+}