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Date:   Wed,  5 Apr 2023 17:40:18 -0700
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Subject: [PATCH 3/3] selftests/bpf: Test allowing NULL buffer in dynptr slice
From:   Daniel Rosenberg <drosen@google.com>
To:     bpf@vger.kernel.org
Cc:     Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        John Fastabend <john.fastabend@gmail.com>,
        Andrii Nakryiko <andrii@kernel.org>,
        Martin KaFai Lau <martin.lau@linux.dev>,
        Song Liu <song@kernel.org>, Yonghong Song <yhs@fb.com>,
        KP Singh <kpsingh@kernel.org>,
        Stanislav Fomichev <sdf@google.com>,
        Hao Luo <haoluo@google.com>, Jiri Olsa <jolsa@kernel.org>,
        Shuah Khan <shuah@kernel.org>,
        Jonathan Corbet <corbet@lwn.net>,
        Joanne Koong <joannelkoong@gmail.com>,
        Mykola Lysenko <mykolal@fb.com>, linux-kernel@vger.kernel.org,
        linux-kselftest@vger.kernel.org, kernel-team@android.com,
        Daniel Rosenberg <drosen@google.com>
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Precedence: bulk

bpf_dynptr_slice(_rw) no longer requires a buffer for verification. If the
buffer is needed, but not present, the function will return NULL.

Signed-off-by: Daniel Rosenberg <drosen@google.com>
---
 .../testing/selftests/bpf/prog_tests/dynptr.c |  1 +
 .../selftests/bpf/progs/dynptr_success.c      | 21 +++++++++++++++++++
 2 files changed, 22 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/dynptr.c b/tools/testing/selftests/bpf/prog_tests/dynptr.c
index d176c34a7d2e..db22cad32657 100644
--- a/tools/testing/selftests/bpf/prog_tests/dynptr.c
+++ b/tools/testing/selftests/bpf/prog_tests/dynptr.c
@@ -20,6 +20,7 @@ static struct {
 	{"test_ringbuf", SETUP_SYSCALL_SLEEP},
 	{"test_skb_readonly", SETUP_SKB_PROG},
 	{"test_dynptr_skb_data", SETUP_SKB_PROG},
+	{"test_dynptr_skb_nobuff", SETUP_SKB_PROG},
 };
 
 static void verify_success(const char *prog_name, enum test_setup_type setup_type)
diff --git a/tools/testing/selftests/bpf/progs/dynptr_success.c b/tools/testing/selftests/bpf/progs/dynptr_success.c
index b2fa6c47ecc0..a059ed8d4590 100644
--- a/tools/testing/selftests/bpf/progs/dynptr_success.c
+++ b/tools/testing/selftests/bpf/progs/dynptr_success.c
@@ -207,3 +207,24 @@ int test_dynptr_skb_data(struct __sk_buff *skb)
 
 	return 1;
 }
+
+SEC("?cgroup_skb/egress")
+int test_dynptr_skb_no_buff(struct __sk_buff *skb)
+{
+	struct bpf_dynptr ptr;
+	__u64 *data;
+
+	if (bpf_dynptr_from_skb(skb, 0, &ptr)) {
+		err = 1;
+		return 1;
+	}
+
+	/* This should return NULL. SKB may require a buffer */
+	data = bpf_dynptr_slice(&ptr, 0, NULL, 1);
+	if (data) {
+		err = 2;
+		return 1;
+	}
+
+	return 1;
+}
-- 
2.40.0.577.gac1e443424-goog