[bpf-next,v2,7/7] selftests/bpf: copy_from_user_dynptr test

Commit Message

Levi Zim via B4 Relay Jan. 25, 2025, 8:29 a.m. UTC

From: Levi Zim <[e-mail]>

This patch adds a test for copy_from_user_dynptr helper,
which tests reading variable length of user memory into a ringbuf
backed dynptr.

Signed-off-by: Levi Zim <[e-mail]>
---
 tools/testing/selftests/bpf/prog_tests/dynptr.c    |  3 ++
 tools/testing/selftests/bpf/progs/dynptr_success.c | 34 ++++++++++++++++++++++
 2 files changed, 37 insertions(+)

Patch

diff --git a/tools/testing/selftests/bpf/prog_tests/dynptr.c b/tools/testing/selftests/bpf/prog_tests/dynptr.c
index a5a61a4c570d803bfca2af3f1a3b7d5eb0b8197f..a0095204609c710d49a6105ebf8be44723fb53d2 100644
--- a/tools/testing/selftests/bpf/prog_tests/dynptr.c
+++ b/tools/testing/selftests/bpf/prog_tests/dynptr.c
@@ -33,6 +33,7 @@  static struct {
 	{"test_dynptr_skb_tp_btf", SETUP_SKB_PROG_TP},
 	{"test_probe_read_kernel_dynptr", SETUP_RINGBUF},
 	{"test_probe_read_user_dynptr", SETUP_RINGBUF},
+	{"test_copy_from_user_dynptr", SETUP_RINGBUF},
 };
 
 static int ringbuf_cb(void *ctx, void *data, size_t len)
@@ -43,6 +44,8 @@  static int ringbuf_cb(void *ctx, void *data, size_t len)
 	if (!ASSERT_EQ(len, skel->data->test_buf.length, "length"))
 		return -E2BIG;
 
+	ASSERT_EQ(skel->bss->err, 0, "err");
+
 	if (!ASSERT_MEMEQ(buf, skel->data->test_buf.buf, len, "ringbuf_cb"))
 		return -EINVAL;
 
diff --git a/tools/testing/selftests/bpf/progs/dynptr_success.c b/tools/testing/selftests/bpf/progs/dynptr_success.c
index 5317860290dccb0862b6a0b94bb6f738c8d92835..10dda58fed66a05ad1b08c8684784fddabe3f4ad 100644
--- a/tools/testing/selftests/bpf/progs/dynptr_success.c
+++ b/tools/testing/selftests/bpf/progs/dynptr_success.c
@@ -639,3 +639,37 @@  int test_probe_read_user_dynptr(void *ctx)
 	bpf_ringbuf_submit_dynptr(&ptr, 0);
 	return 0;
 }
+
+SEC("?fentry.s/" SYS_PREFIX "sys_nanosleep")
+int test_copy_from_user_dynptr(void *ctx)
+{
+	struct bpf_dynptr ptr;
+	int copy_len;
+
+	if (bpf_get_current_pid_tgid() >> 32 != pid)
+		return 0;
+
+	err = bpf_probe_read_user(&copy_len, sizeof(copy_len), &user_ptr->length);
+	if (err < 0 || copy_len < 0) {
+		err = 1;
+		return 0;
+	}
+
+	if (copy_len > MAX_BUFFER_LEN)
+		copy_len = MAX_BUFFER_LEN;
+
+	bpf_ringbuf_reserve_dynptr(&ringbuf, copy_len, 0, &ptr);
+
+	if (-E2BIG != bpf_copy_from_user_dynptr(&ptr, 0, MAX_BUFFER_LEN + 1,
+		&user_ptr->buf, 0)) {
+		err = 2;
+		goto cleanup;
+	}
+
+	err = bpf_copy_from_user_dynptr(&ptr, 0, copy_len,
+		&user_ptr->buf, 0);
+
+cleanup:
+	bpf_ringbuf_submit_dynptr(&ptr, 0);
+	return 0;
+}