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From: Alban Crequy <albancrequy@linux.microsoft.com>
To: bpf@vger.kernel.org
Cc: stable@vger.kernel.org, albancrequy@linux.microsoft.com,
	flaniel@linux.microsoft.com, akpm@linux-foundation.org,
	andrii@kernel.org, ast@kernel.org, daniel@iogearbox.net,
	haoluo@google.com, john.fastabend@gmail.com, jolsa@kernel.org,
	kpsingh@kernel.org, linux-kernel@vger.kernel.org,
	linux-kselftest@vger.kernel.org, linux-mm@kvack.org,
	martin.lau@linux.dev, mykolal@fb.com, sdf@google.com,
	shuah@kernel.org, song@kernel.org, yhs@fb.com
Subject: [PATCH bpf v2 2/2] selftests: bpf: add a test when bpf_probe_read_kernel_str() returns EFAULT
Date: Thu, 10 Nov 2022 09:56:14 +0100	[thread overview]
Message-ID: <20221110085614.111213-3-albancrequy@linux.microsoft.com> (raw)
In-Reply-To: <20221110085614.111213-1-albancrequy@linux.microsoft.com>

This commit tests previous fix of bpf_probe_read_kernel_str().

The BPF helper bpf_probe_read_kernel_str should return -EFAULT when
given a bad source pointer and the target buffer should only be modified
to make the string NULL terminated.

bpf_probe_read_kernel_str() was previously inserting a NULL before the
beginning of the dst buffer. This test should ensure that the
implementation stays correct for now on.

Without the fix, this test will fail as follows:
  $ cd tools/testing/selftests/bpf
  $ make
  $ sudo ./test_progs --name=varlen
  ...
  test_varlen:FAIL:check got 0 != exp 66

Signed-off-by: Alban Crequy <albancrequy@linux.microsoft.com>
Signed-off-by: Francis Laniel <flaniel@linux.microsoft.com>
Acked-by: Yonghong Song <yhs@fb.com>

Changes v1 to v2:
- add ack tag
- fix my email
- rebase on bpf tree and tag for bpf tree
---
 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;
 }
 
-- 
2.36.1


  parent reply	other threads:[~2022-11-10  8:57 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-11-10  8:56 [PATCH bpf v2 0/2] Fix offset when fault occurs in strncpy_from_kernel_nofault() Alban Crequy
2022-11-10  8:56 ` [PATCH bpf v2 1/2] maccess: fix writing offset in case of fault " Alban Crequy
2022-11-10  8:56 ` Alban Crequy [this message]
2022-11-10  8:57   ` [PATCH bpf v2 2/2] selftests: bpf: add a test when bpf_probe_read_kernel_str() returns EFAULT kernel test robot
2022-11-11 20:10 ` [PATCH bpf v2 0/2] Fix offset when fault occurs in strncpy_from_kernel_nofault() patchwork-bot+netdevbpf

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