linux-kernel - [RFC PATCH v1 2/2] selftests: bpf: add a test when bpf_probe_read_kernel

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Date:   Tue,  8 Nov 2022 20:52:07 +0100
From:   Francis Laniel <flaniel@...ux.microsoft.com>
To:     linux-kernel@...r.kernel.org
Cc:     Alban Crequy <alban.crequy@...il.com>,
        Alban Crequy <albancrequy@...rosoft.com>,
        Francis Laniel <flaniel@...ux.microsoft.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        Song Liu <song@...nel.org>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Stanislav Fomichev <sdf@...gle.com>,
        Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
        Mykola Lysenko <mykolal@...com>, Shuah Khan <shuah@...nel.org>,
        linux-mm@...ck.org, bpf@...r.kernel.org,
        linux-kselftest@...r.kernel.org
Subject: [RFC PATCH v1 2/2] selftests: bpf: add a test when bpf_probe_read_kernel_str() returns EFAULT

From: Alban Crequy <albancrequy@...rosoft.com>

This commit tests previous fix of bpf_probe_read_kernel_str().

Signed-off-by: Alban Crequy <albancrequy@...rosoft.com>
Signed-off-by: Francis Laniel <flaniel@...ux.microsoft.com>
---
 tools/testing/selftests/bpf/prog_tests/varlen.c | 7 +++++++
 tools/testing/selftests/bpf/progs/test_varlen.c | 5 +++++
 2 files changed, 12 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/varlen.c b/tools/testing/selftests/bpf/prog_tests/varlen.c
index dd324b4933db..4d7056f8f177 100644
--- a/tools/testing/selftests/bpf/prog_tests/varlen.c
+++ b/tools/testing/selftests/bpf/prog_tests/varlen.c
@@ -63,6 +63,13 @@ void test_varlen(void)
 	CHECK_VAL(data->total4, size1 + size2);
 	CHECK(memcmp(data->payload4, exp_str, size1 + size2), "content_check",
 	      "doesn't match!\n");
+
+	CHECK_VAL(bss->ret_bad_read, -EFAULT);
+	CHECK_VAL(data->payload_bad[0], 0x42);
+	CHECK_VAL(data->payload_bad[1], 0x42);
+	CHECK_VAL(data->payload_bad[2], 0);
+	CHECK_VAL(data->payload_bad[3], 0x42);
+	CHECK_VAL(data->payload_bad[4], 0x42);
 cleanup:
 	test_varlen__destroy(skel);
 }
diff --git a/tools/testing/selftests/bpf/progs/test_varlen.c b/tools/testing/selftests/bpf/progs/test_varlen.c
index 3987ff174f1f..20eb7d422c41 100644
--- a/tools/testing/selftests/bpf/progs/test_varlen.c
+++ b/tools/testing/selftests/bpf/progs/test_varlen.c
@@ -19,6 +19,7 @@ __u64 payload1_len1 = 0;
 __u64 payload1_len2 = 0;
 __u64 total1 = 0;
 char payload1[MAX_LEN + MAX_LEN] = {};
+__u64 ret_bad_read = 0;
 
 /* .data */
 int payload2_len1 = -1;
@@ -36,6 +37,8 @@ int payload4_len2 = -1;
 int total4= -1;
 char payload4[MAX_LEN + MAX_LEN] = { 1 };
 
+char payload_bad[5] = { 0x42, 0x42, 0x42, 0x42, 0x42 };
+
 SEC("raw_tp/sys_enter")
 int handler64_unsigned(void *regs)
 {
@@ -61,6 +64,8 @@ int handler64_unsigned(void *regs)
 
 	total1 = payload - (void *)payload1;
 
+	ret_bad_read = bpf_probe_read_kernel_str(payload_bad + 2, 1, (void *) -1);
+
 	return 0;
 }
 
-- 
2.25.1