[PATCH v4 11/11] selftests/coredump: add tests for AF_UNIX coredumps

[Christian Brauner <brauner@kernel.org>]

Add a simple test for generating coredumps via AF_UNIX sockets.

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 tools/testing/selftests/coredump/stackdump_test.c | 273 +++++++++++++++++++++-
 1 file changed, 272 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/coredump/stackdump_test.c b/tools/testing/selftests/coredump/stackdump_test.c
index fe3c728cd6be..a86f4ba0a367 100644
--- a/tools/testing/selftests/coredump/stackdump_test.c
+++ b/tools/testing/selftests/coredump/stackdump_test.c
@@ -5,10 +5,15 @@
 #include <linux/limits.h>
 #include <pthread.h>
 #include <string.h>
+#include <sys/mount.h>
 #include <sys/resource.h>
+#include <sys/stat.h>
+#include <sys/socket.h>
+#include <sys/un.h>
 #include <unistd.h>
 
 #include "../kselftest_harness.h"
+#include "../pidfd/pidfd.h"
 
 #define STACKDUMP_FILE "stack_values"
 #define STACKDUMP_SCRIPT "stackdump"
@@ -35,6 +40,7 @@ static void crashing_child(void)
 FIXTURE(coredump)
 {
 	char original_core_pattern[256];
+	pid_t pid_coredump_server;
 };
 
 FIXTURE_SETUP(coredump)
@@ -44,6 +50,7 @@ FIXTURE_SETUP(coredump)
 	char *dir;
 	int ret;
 
+	self->pid_coredump_server = -ESRCH;
 	file = fopen("/proc/sys/kernel/core_pattern", "r");
 	ASSERT_NE(NULL, file);
 
@@ -61,10 +68,15 @@ FIXTURE_TEARDOWN(coredump)
 {
 	const char *reason;
 	FILE *file;
-	int ret;
+	int ret, status;
 
 	unlink(STACKDUMP_FILE);
 
+	if (self->pid_coredump_server > 0) {
+		kill(self->pid_coredump_server, SIGTERM);
+		waitpid(self->pid_coredump_server, &status, 0);
+	}
+
 	file = fopen("/proc/sys/kernel/core_pattern", "w");
 	if (!file) {
 		reason = "Unable to open core_pattern";
@@ -154,4 +166,263 @@ TEST_F_TIMEOUT(coredump, stackdump, 120)
 	fclose(file);
 }
 
+TEST_F(coredump, socket)
+{
+	int fd, pidfd, ret, status;
+	FILE *file;
+	pid_t pid, pid_coredump_server;
+	struct stat st;
+	char core_file[PATH_MAX];
+	struct pidfd_info info = {};
+	int ipc_sockets[2];
+	char c;
+
+	ASSERT_EQ(unshare(CLONE_NEWNS), 0);
+	ASSERT_EQ(mount(NULL, "/", NULL, MS_PRIVATE | MS_REC, NULL), 0);
+	ASSERT_EQ(mount(NULL, "/tmp", "tmpfs", 0, NULL), 0);
+
+	file = fopen("/proc/sys/kernel/core_pattern", "w");
+	ASSERT_NE(NULL, file);
+
+	ret = fprintf(file, "@linuxafsk/coredump.socket");
+	ASSERT_EQ(ret, strlen("@linuxafsk/coredump.socket"));
+	ASSERT_EQ(fclose(file), 0);
+
+	ret = socketpair(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0, ipc_sockets);
+	ASSERT_EQ(ret, 0);
+
+	pid_coredump_server = fork();
+	ASSERT_GE(pid_coredump_server, 0);
+	if (pid_coredump_server == 0) {
+		int fd_socket, fd_coredump, fd_peer_pidfd, fd_core_file;
+		__u64 peer_cookie;
+		socklen_t fd_peer_pidfd_len, peer_cookie_len;
+		static const struct sockaddr_un coredump_sk = {
+			.sun_family = AF_UNIX,
+			.sun_path = "\0linuxafsk/coredump.socket",
+		};
+		static const size_t coredump_sk_len =
+			offsetof(struct sockaddr_un, sun_path) +
+			sizeof("linuxafsk/coredump.socket"); /* +1 for leading NUL */
+
+		close(ipc_sockets[0]);
+
+		fd_socket = socket(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0);
+		if (fd_socket < 0)
+			_exit(EXIT_FAILURE);
+
+		ret = bind(fd_socket, (const struct sockaddr *)&coredump_sk, coredump_sk_len);
+		if (ret < 0) {
+			fprintf(stderr, "Failed to bind coredump socket\n");
+			close(fd_socket);
+			close(ipc_sockets[1]);
+			_exit(EXIT_FAILURE);
+		}
+
+		ret = listen(fd_socket, 1);
+		if (ret < 0) {
+			fprintf(stderr, "Failed to listen on coredump socket\n");
+			close(fd_socket);
+			close(ipc_sockets[1]);
+			_exit(EXIT_FAILURE);
+		}
+
+		if (write_nointr(ipc_sockets[1], "1", 1) < 0) {
+			close(fd_socket);
+			close(ipc_sockets[1]);
+			_exit(EXIT_FAILURE);
+		}
+
+		close(ipc_sockets[1]);
+
+		fd_coredump = accept4(fd_socket, NULL, NULL, SOCK_CLOEXEC);
+		if (fd_coredump < 0) {
+			fprintf(stderr, "Failed to accept coredump socket connection\n");
+			close(fd_socket);
+			_exit(EXIT_FAILURE);
+		}
+
+		peer_cookie_len = sizeof(peer_cookie);
+		ret = getsockopt(fd_coredump, SOL_SOCKET, SO_COOKIE,
+				 &peer_cookie, &peer_cookie_len);
+		if (ret < 0) {
+			fprintf(stderr, "%m - Failed to retrieve cookie for coredump socket connection\n");
+			close(fd_coredump);
+			close(fd_socket);
+			_exit(EXIT_FAILURE);
+		}
+
+		fd_peer_pidfd_len = sizeof(fd_peer_pidfd);
+		ret = getsockopt(fd_coredump, SOL_SOCKET, SO_PEERPIDFD,
+				 &fd_peer_pidfd, &fd_peer_pidfd_len);
+		if (ret < 0) {
+			fprintf(stderr, "%m - Failed to retrieve peer pidfd for coredump socket connection\n");
+			close(fd_coredump);
+			close(fd_socket);
+			_exit(EXIT_FAILURE);
+		}
+
+		memset(&info, 0, sizeof(info));
+		info.mask = PIDFD_INFO_EXIT | PIDFD_INFO_COREDUMP;
+		ret = ioctl(fd_peer_pidfd, PIDFD_GET_INFO, &info);
+		if (ret < 0) {
+			fprintf(stderr, "Failed to retrieve pidfd info from peer pidfd for coredump socket connection\n");
+			close(fd_coredump);
+			close(fd_socket);
+			close(fd_peer_pidfd);
+			_exit(EXIT_FAILURE);
+		}
+
+		if (!(info.mask & PIDFD_INFO_COREDUMP)) {
+			fprintf(stderr, "Missing coredump information from coredumping task\n");
+			close(fd_coredump);
+			close(fd_socket);
+			close(fd_peer_pidfd);
+			_exit(EXIT_FAILURE);
+		}
+
+		if (!(info.coredump_mask & PIDFD_COREDUMPED)) {
+			fprintf(stderr, "Received connection from non-coredumping task\n");
+			close(fd_coredump);
+			close(fd_socket);
+			close(fd_peer_pidfd);
+			_exit(EXIT_FAILURE);
+		}
+
+		if (!info.coredump_cookie) {
+			fprintf(stderr, "Missing coredump cookie\n");
+			close(fd_coredump);
+			close(fd_socket);
+			close(fd_peer_pidfd);
+			_exit(EXIT_FAILURE);
+		}
+
+		if (info.coredump_cookie != peer_cookie) {
+			fprintf(stderr, "Mismatching coredump cookies\n");
+			close(fd_coredump);
+			close(fd_socket);
+			close(fd_peer_pidfd);
+			_exit(EXIT_FAILURE);
+		}
+
+		fd_core_file = creat("/tmp/coredump.file", 0644);
+		if (fd_core_file < 0) {
+			fprintf(stderr, "Failed to create coredump file\n");
+			close(fd_coredump);
+			close(fd_socket);
+			close(fd_peer_pidfd);
+			_exit(EXIT_FAILURE);
+		}
+
+		for (;;) {
+			char buffer[4096];
+			ssize_t bytes_read, bytes_write;
+
+			bytes_read = read(fd_coredump, buffer, sizeof(buffer));
+			if (bytes_read < 0) {
+				close(fd_coredump);
+				close(fd_socket);
+				close(fd_peer_pidfd);
+				close(fd_core_file);
+				_exit(EXIT_FAILURE);
+			}
+
+			if (bytes_read == 0)
+				break;
+
+			bytes_write = write(fd_core_file, buffer, bytes_read);
+			if (bytes_read != bytes_write) {
+				close(fd_coredump);
+				close(fd_socket);
+				close(fd_peer_pidfd);
+				close(fd_core_file);
+				_exit(EXIT_FAILURE);
+			}
+		}
+
+		close(fd_coredump);
+		close(fd_socket);
+		close(fd_peer_pidfd);
+		close(fd_core_file);
+		_exit(EXIT_SUCCESS);
+	}
+	self->pid_coredump_server = pid_coredump_server;
+
+	EXPECT_EQ(close(ipc_sockets[1]), 0);
+	ASSERT_EQ(read_nointr(ipc_sockets[0], &c, 1), 1);
+	EXPECT_EQ(close(ipc_sockets[0]), 0);
+
+	pid = fork();
+	ASSERT_GE(pid, 0);
+	if (pid == 0)
+		crashing_child();
+
+	pidfd = sys_pidfd_open(pid, 0);
+	ASSERT_GE(pidfd, 0);
+
+	waitpid(pid, &status, 0);
+	ASSERT_TRUE(WIFSIGNALED(status));
+	ASSERT_TRUE(WCOREDUMP(status));
+
+	info.mask = PIDFD_INFO_EXIT | PIDFD_INFO_COREDUMP;
+	ASSERT_EQ(ioctl(pidfd, PIDFD_GET_INFO, &info), 0);
+	ASSERT_GT((info.mask & PIDFD_INFO_COREDUMP), 0);
+	ASSERT_GT((info.coredump_mask & PIDFD_COREDUMPED), 0);
+
+	waitpid(pid_coredump_server, &status, 0);
+	self->pid_coredump_server = -ESRCH;
+	ASSERT_TRUE(WIFEXITED(status));
+	ASSERT_EQ(WEXITSTATUS(status), 0);
+
+	ASSERT_EQ(stat("/tmp/coredump.file", &st), 0);
+	ASSERT_GT(st.st_size, 0);
+	/*
+	 * We should somehow validate the produced core file.
+	 * For now just allow for visual inspection
+	 */
+	system("file /tmp/coredump.file");
+}
+
+TEST_F(coredump, socket_econnrefused)
+{
+	int fd_socket;
+	static const struct sockaddr_un linuxafsk = {
+		.sun_family = AF_UNIX,
+		.sun_path = "\0linuxafsk/",
+	};
+	static const size_t linuxafsk_len =
+		offsetof(struct sockaddr_un, sun_path) +
+		sizeof("linuxafsk/"); /* +1 for leading NUL */
+
+	fd_socket = socket(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0);
+	ASSERT_GT(fd_socket, 0);
+
+	ASSERT_NE(bind(fd_socket, (const struct sockaddr *)&linuxafsk, linuxafsk_len), 0);
+	ASSERT_EQ(errno, ECONNREFUSED);
+	EXPECT_EQ(close(fd_socket), 0);
+}
+
+TEST_F(coredump, socket_econnrefused_privilege)
+{
+	int fd_socket;
+	static const struct sockaddr_un linuxafsk = {
+		.sun_family = AF_UNIX,
+		.sun_path = "\0linuxafsk/nope",
+	};
+	static const size_t linuxafsk_len =
+		offsetof(struct sockaddr_un, sun_path) +
+		sizeof("linuxafsk/nope"); /* +1 for leading NUL */
+
+	ASSERT_EQ(seteuid(1234), 0);
+
+	fd_socket = socket(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0);
+	ASSERT_GT(fd_socket, 0);
+
+	ASSERT_NE(bind(fd_socket, (const struct sockaddr *)&linuxafsk, linuxafsk_len), 0);
+	ASSERT_EQ(errno, ECONNREFUSED);
+	EXPECT_EQ(close(fd_socket), 0);
+
+	ASSERT_EQ(seteuid(0), 0);
+}
+
 TEST_HARNESS_MAIN

-- 
2.47.2