[RFC PATCH v1 2/2] selftests: bpf: add a test when bpf_probe_read_kernel_str() returns EFAULT

[Francis Laniel <flaniel@linux.microsoft.com>]

From: Alban Crequy <albancrequy@microsoft.com>

This commit tests previous fix of bpf_probe_read_kernel_str().

Signed-off-by: Alban Crequy <albancrequy@microsoft.com>
Signed-off-by: Francis Laniel <flaniel@linux.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