[PATCH v3 1/1] selftests/landlock: skip ptrace_test according to YAMA

[jeffxu@chromium.org]

From: Jeff Xu <jeffxu@google.com>

Add check for yama setting for ptrace_test.

Signed-off-by: Jeff Xu <jeffxu@google.com>
---
 .../testing/selftests/landlock/ptrace_test.c  | 173 ++++++++++++------
 1 file changed, 112 insertions(+), 61 deletions(-)

diff --git a/tools/testing/selftests/landlock/ptrace_test.c b/tools/testing/selftests/landlock/ptrace_test.c
index c28ef98ff3ac..0056815deef8 100644
--- a/tools/testing/selftests/landlock/ptrace_test.c
+++ b/tools/testing/selftests/landlock/ptrace_test.c
@@ -60,6 +60,23 @@ static int test_ptrace_read(const pid_t pid)
 	return 0;
 }
 
+static int get_yama_ptrace_scope(void)
+{
+	int ret = -1;
+	char buf[2] = {};
+	int fd = open("/proc/sys/kernel/yama/ptrace_scope", O_RDONLY);
+
+	if (fd < 0)
+		return 0;
+
+	if (read(fd, &buf, 1) < 0)
+		return -1;
+
+	ret = atoi(buf);
+	close(fd);
+	return ret;
+}
+
 /* clang-format off */
 FIXTURE(hierarchy) {};
 /* clang-format on */
@@ -69,6 +86,7 @@ FIXTURE_VARIANT(hierarchy)
 	const bool domain_both;
 	const bool domain_parent;
 	const bool domain_child;
+	const int  yama_ptrace_scope_max_supported;
 };
 
 /*
@@ -93,6 +111,7 @@ FIXTURE_VARIANT_ADD(hierarchy, allow_without_domain) {
 	.domain_both = false,
 	.domain_parent = false,
 	.domain_child = false,
+	.yama_ptrace_scope_max_supported = 0,
 };
 
 /*
@@ -110,6 +129,7 @@ FIXTURE_VARIANT_ADD(hierarchy, allow_with_one_domain) {
 	.domain_both = false,
 	.domain_parent = false,
 	.domain_child = true,
+	.yama_ptrace_scope_max_supported = 1,
 };
 
 /*
@@ -126,6 +146,7 @@ FIXTURE_VARIANT_ADD(hierarchy, deny_with_parent_domain) {
 	.domain_both = false,
 	.domain_parent = true,
 	.domain_child = false,
+	.yama_ptrace_scope_max_supported = 0,
 };
 
 /*
@@ -143,6 +164,7 @@ FIXTURE_VARIANT_ADD(hierarchy, deny_with_sibling_domain) {
 	.domain_both = false,
 	.domain_parent = true,
 	.domain_child = true,
+	.yama_ptrace_scope_max_supported = 2,
 };
 
 /*
@@ -160,6 +182,7 @@ FIXTURE_VARIANT_ADD(hierarchy, allow_sibling_domain) {
 	.domain_both = true,
 	.domain_parent = false,
 	.domain_child = false,
+	.yama_ptrace_scope_max_supported = 0,
 };
 
 /*
@@ -178,6 +201,7 @@ FIXTURE_VARIANT_ADD(hierarchy, allow_with_nested_domain) {
 	.domain_both = true,
 	.domain_parent = false,
 	.domain_child = true,
+	.yama_ptrace_scope_max_supported = 1,
 };
 
 /*
@@ -196,6 +220,7 @@ FIXTURE_VARIANT_ADD(hierarchy, deny_with_nested_and_parent_domain) {
 	.domain_both = true,
 	.domain_parent = true,
 	.domain_child = false,
+	.yama_ptrace_scope_max_supported = 0,
 };
 
 /*
@@ -216,6 +241,7 @@ FIXTURE_VARIANT_ADD(hierarchy, deny_with_forked_domain) {
 	.domain_both = true,
 	.domain_parent = true,
 	.domain_child = true,
+	.yama_ptrace_scope_max_supported = 2,
 };
 
 FIXTURE_SETUP(hierarchy)
@@ -232,8 +258,20 @@ TEST_F(hierarchy, trace)
 	pid_t child, parent;
 	int status, err_proc_read;
 	int pipe_child[2], pipe_parent[2];
+	int yama_ptrace_scope;
 	char buf_parent;
 	long ret;
+	bool can_trace_child, can_trace_parent;
+
+	yama_ptrace_scope = get_yama_ptrace_scope();
+	ASSERT_LE(0, yama_ptrace_scope);
+
+	if (yama_ptrace_scope >= 3)
+		SKIP(return, "Yama forbids any ptrace use (scope %d)", yama_ptrace_scope);
+
+	can_trace_child = !variant->domain_parent && (yama_ptrace_scope < 2);
+	can_trace_parent = !variant->domain_child && (yama_ptrace_scope < 1);
+	TH_LOG("can_trace_child:%d, can_trace_parent:%d", can_trace_child, can_trace_parent);
 
 	/*
 	 * Removes all effective and permitted capabilities to not interfere
@@ -258,6 +296,7 @@ TEST_F(hierarchy, trace)
 
 		ASSERT_EQ(0, close(pipe_parent[1]));
 		ASSERT_EQ(0, close(pipe_child[0]));
+
 		if (variant->domain_child)
 			create_domain(_metadata);
 
@@ -265,43 +304,47 @@ TEST_F(hierarchy, trace)
 		ASSERT_EQ(1, read(pipe_parent[0], &buf_child, 1));
 
 		/* Tests PTRACE_ATTACH and PTRACE_MODE_READ on the parent. */
-		err_proc_read = test_ptrace_read(parent);
-		ret = ptrace(PTRACE_ATTACH, parent, NULL, 0);
-		if (variant->domain_child) {
-			EXPECT_EQ(-1, ret);
-			EXPECT_EQ(EPERM, errno);
-			EXPECT_EQ(EACCES, err_proc_read);
-		} else {
-			EXPECT_EQ(0, ret);
-			EXPECT_EQ(0, err_proc_read);
-		}
-		if (ret == 0) {
-			ASSERT_EQ(parent, waitpid(parent, &status, 0));
-			ASSERT_EQ(1, WIFSTOPPED(status));
-			ASSERT_EQ(0, ptrace(PTRACE_DETACH, parent, NULL, 0));
+		if (can_trace_parent) {
+			err_proc_read = test_ptrace_read(parent);
+			ret = ptrace(PTRACE_ATTACH, parent, NULL, 0);
+			if (variant->domain_child) {
+				EXPECT_EQ(-1, ret);
+				EXPECT_EQ(EPERM, errno);
+				EXPECT_EQ(EACCES, err_proc_read);
+			} else {
+				EXPECT_EQ(0, ret);
+				EXPECT_EQ(0, err_proc_read);
+			}
+			if (ret == 0) {
+				ASSERT_EQ(parent, waitpid(parent, &status, 0));
+				ASSERT_EQ(1, WIFSTOPPED(status));
+				ASSERT_EQ(0, ptrace(PTRACE_DETACH, parent, NULL, 0));
+			}
 		}
 
 		/* Tests child PTRACE_TRACEME. */
-		ret = ptrace(PTRACE_TRACEME);
-		if (variant->domain_parent) {
-			EXPECT_EQ(-1, ret);
-			EXPECT_EQ(EPERM, errno);
-		} else {
-			EXPECT_EQ(0, ret);
+		if (can_trace_child) {
+			ret = ptrace(PTRACE_TRACEME);
+			if (variant->domain_parent) {
+				EXPECT_EQ(-1, ret);
+				EXPECT_EQ(EPERM, errno);
+			} else {
+				EXPECT_EQ(0, ret);
+			}
+
+			/*
+			 * Signals that the PTRACE_ATTACH test is done and the
+			 * PTRACE_TRACEME test is ongoing.
+			 */
+			ASSERT_EQ(1, write(pipe_child[1], ".", 1));
+
+			if (!variant->domain_parent)
+				ASSERT_EQ(0, raise(SIGSTOP));
+
+			/* Waits for the parent PTRACE_ATTACH test. */
+			ASSERT_EQ(1, read(pipe_parent[0], &buf_child, 1));
 		}
 
-		/*
-		 * Signals that the PTRACE_ATTACH test is done and the
-		 * PTRACE_TRACEME test is ongoing.
-		 */
-		ASSERT_EQ(1, write(pipe_child[1], ".", 1));
-
-		if (!variant->domain_parent) {
-			ASSERT_EQ(0, raise(SIGSTOP));
-		}
-
-		/* Waits for the parent PTRACE_ATTACH test. */
-		ASSERT_EQ(1, read(pipe_parent[0], &buf_child, 1));
 		_exit(_metadata->passed ? EXIT_SUCCESS : EXIT_FAILURE);
 		return;
 	}
@@ -318,42 +361,50 @@ TEST_F(hierarchy, trace)
 	 * Waits for the child to test PTRACE_ATTACH on the parent and start
 	 * testing PTRACE_TRACEME.
 	 */
-	ASSERT_EQ(1, read(pipe_child[0], &buf_parent, 1));
-
-	/* Tests child PTRACE_TRACEME. */
-	if (!variant->domain_parent) {
-		ASSERT_EQ(child, waitpid(child, &status, 0));
-		ASSERT_EQ(1, WIFSTOPPED(status));
-		ASSERT_EQ(0, ptrace(PTRACE_DETACH, child, NULL, 0));
-	} else {
-		/* The child should not be traced by the parent. */
-		EXPECT_EQ(-1, ptrace(PTRACE_DETACH, child, NULL, 0));
-		EXPECT_EQ(ESRCH, errno);
-	}
+	if (can_trace_child) {
+		ASSERT_EQ(1, read(pipe_child[0], &buf_parent, 1));
 
-	/* Tests PTRACE_ATTACH and PTRACE_MODE_READ on the child. */
-	err_proc_read = test_ptrace_read(child);
-	ret = ptrace(PTRACE_ATTACH, child, NULL, 0);
-	if (variant->domain_parent) {
-		EXPECT_EQ(-1, ret);
-		EXPECT_EQ(EPERM, errno);
-		EXPECT_EQ(EACCES, err_proc_read);
-	} else {
-		EXPECT_EQ(0, ret);
-		EXPECT_EQ(0, err_proc_read);
-	}
-	if (ret == 0) {
-		ASSERT_EQ(child, waitpid(child, &status, 0));
-		ASSERT_EQ(1, WIFSTOPPED(status));
-		ASSERT_EQ(0, ptrace(PTRACE_DETACH, child, NULL, 0));
+		/* Tests child PTRACE_TRACEME. */
+		if (!variant->domain_parent) {
+			ASSERT_EQ(child, waitpid(child, &status, 0));
+			ASSERT_EQ(1, WIFSTOPPED(status));
+			ASSERT_EQ(0, ptrace(PTRACE_DETACH, child, NULL, 0));
+		} else {
+			/* The child should not be traced by the parent. */
+			EXPECT_EQ(-1, ptrace(PTRACE_DETACH, child, NULL, 0));
+			EXPECT_EQ(ESRCH, errno);
+		}
+
+		/* Tests PTRACE_ATTACH and PTRACE_MODE_READ on the child. */
+		err_proc_read = test_ptrace_read(child);
+		ret = ptrace(PTRACE_ATTACH, child, NULL, 0);
+		if (variant->domain_parent) {
+			EXPECT_EQ(-1, ret);
+			EXPECT_EQ(EPERM, errno);
+			EXPECT_EQ(EACCES, err_proc_read);
+		} else {
+			EXPECT_EQ(0, ret);
+			EXPECT_EQ(0, err_proc_read);
+		}
+		if (ret == 0) {
+			ASSERT_EQ(child, waitpid(child, &status, 0));
+			ASSERT_EQ(1, WIFSTOPPED(status));
+			ASSERT_EQ(0, ptrace(PTRACE_DETACH, child, NULL, 0));
+		}
+
+		/* Signals that the parent PTRACE_ATTACH test is done. */
+		ASSERT_EQ(1, write(pipe_parent[1], ".", 1));
 	}
 
-	/* Signals that the parent PTRACE_ATTACH test is done. */
-	ASSERT_EQ(1, write(pipe_parent[1], ".", 1));
 	ASSERT_EQ(child, waitpid(child, &status, 0));
 	if (WIFSIGNALED(status) || !WIFEXITED(status) ||
 	    WEXITSTATUS(status) != EXIT_SUCCESS)
 		_metadata->passed = 0;
+
+	if (yama_ptrace_scope > 0)
+		SKIP(return, "Incomplete tests due to Yama restrictions (ptrace_scope:%d)",
+			yama_ptrace_scope);
+
 }
 
 TEST_HARNESS_MAIN
-- 
2.39.0.314.g84b9a713c41-goog