1 files changed, 1450 insertions, 242 deletions

diff --git a/tools/testing/selftests/coredump/stackdump_test.c b/tools/testing/selftests/coredump/stackdump_test.c
index 9984413be9f0..5a5a7a5f7e1d 100644
--- a/tools/testing/selftests/coredump/stackdump_test.c
+++ b/tools/testing/selftests/coredump/stackdump_test.c
@@ -1,12 +1,18 @@
 // SPDX-License-Identifier: GPL-2.0
 
+#include <assert.h>
 #include <fcntl.h>
 #include <inttypes.h>
 #include <libgen.h>
+#include <limits.h>
+#include <linux/coredump.h>
+#include <linux/fs.h>
 #include <linux/limits.h>
 #include <pthread.h>
 #include <string.h>
 #include <sys/mount.h>
+#include <poll.h>
+#include <sys/epoll.h>
 #include <sys/resource.h>
 #include <sys/stat.h>
 #include <sys/socket.h>
@@ -14,16 +20,23 @@
 #include <unistd.h>
 
 #include "../kselftest_harness.h"
+#include "../filesystems/wrappers.h"
 #include "../pidfd/pidfd.h"
 
 #define STACKDUMP_FILE "stack_values"
 #define STACKDUMP_SCRIPT "stackdump"
 #define NUM_THREAD_SPAWN 128
 
+#ifndef PAGE_SIZE
+#define PAGE_SIZE 4096
+#endif
+
 static void *do_nothing(void *)
 {
 	while (1)
 		pause();
+
+	return NULL;
 }
 
 static void crashing_child(void)
@@ -42,16 +55,32 @@ FIXTURE(coredump)
 {
 	char original_core_pattern[256];
 	pid_t pid_coredump_server;
+	int fd_tmpfs_detached;
 };
 
+static int create_detached_tmpfs(void)
+{
+	int fd_context, fd_tmpfs;
+
+	fd_context = sys_fsopen("tmpfs", 0);
+	if (fd_context < 0)
+		return -1;
+
+	if (sys_fsconfig(fd_context, FSCONFIG_CMD_CREATE, NULL, NULL, 0) < 0)
+		return -1;
+
+	fd_tmpfs = sys_fsmount(fd_context, 0, 0);
+	close(fd_context);
+	return fd_tmpfs;
+}
+
 FIXTURE_SETUP(coredump)
 {
-	char buf[PATH_MAX];
 	FILE *file;
-	char *dir;
 	int ret;
 
 	self->pid_coredump_server = -ESRCH;
+	self->fd_tmpfs_detached = -1;
 	file = fopen("/proc/sys/kernel/core_pattern", "r");
 	ASSERT_NE(NULL, file);
 
@@ -60,6 +89,8 @@ FIXTURE_SETUP(coredump)
 	ASSERT_LT(ret, sizeof(self->original_core_pattern));
 
 	self->original_core_pattern[ret] = '\0';
+	self->fd_tmpfs_detached = create_detached_tmpfs();
+	ASSERT_GE(self->fd_tmpfs_detached, 0);
 
 	ret = fclose(file);
 	ASSERT_EQ(0, ret);
@@ -98,6 +129,15 @@ FIXTURE_TEARDOWN(coredump)
 		goto fail;
 	}
 
+	if (self->fd_tmpfs_detached >= 0) {
+		ret = close(self->fd_tmpfs_detached);
+		if (ret < 0) {
+			reason = "Unable to close detached tmpfs";
+			goto fail;
+		}
+		self->fd_tmpfs_detached = -1;
+	}
+
 	return;
 fail:
 	/* This should never happen */
@@ -106,11 +146,10 @@ fail:
 
 TEST_F_TIMEOUT(coredump, stackdump, 120)
 {
-	struct sigaction action = {};
 	unsigned long long stack;
 	char *test_dir, *line;
 	size_t line_length;
-	char buf[PATH_MAX];
+	char buf[PAGE_SIZE];
 	int ret, i, status;
 	FILE *file;
 	pid_t pid;
@@ -169,153 +208,166 @@ TEST_F_TIMEOUT(coredump, stackdump, 120)
 	fclose(file);
 }
 
+static int create_and_listen_unix_socket(const char *path)
+{
+	struct sockaddr_un addr = {
+		.sun_family = AF_UNIX,
+	};
+	assert(strlen(path) < sizeof(addr.sun_path) - 1);
+	strncpy(addr.sun_path, path, sizeof(addr.sun_path) - 1);
+	size_t addr_len =
+		offsetof(struct sockaddr_un, sun_path) + strlen(path) + 1;
+	int fd, ret;
+
+	fd = socket(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0);
+	if (fd < 0)
+		goto out;
+
+	ret = bind(fd, (const struct sockaddr *)&addr, addr_len);
+	if (ret < 0)
+		goto out;
+
+	ret = listen(fd, 128);
+	if (ret < 0)
+		goto out;
+
+	return fd;
+
+out:
+	if (fd >= 0)
+		close(fd);
+	return -1;
+}
+
+static bool set_core_pattern(const char *pattern)
+{
+	int fd;
+	ssize_t ret;
+
+	fd = open("/proc/sys/kernel/core_pattern", O_WRONLY | O_CLOEXEC);
+	if (fd < 0)
+		return false;
+
+	ret = write(fd, pattern, strlen(pattern));
+	close(fd);
+	if (ret < 0)
+		return false;
+
+	fprintf(stderr, "Set core_pattern to '%s' | %zu == %zu\n", pattern, ret, strlen(pattern));
+	return ret == strlen(pattern);
+}
+
+static int get_peer_pidfd(int fd)
+{
+	int fd_peer_pidfd;
+	socklen_t fd_peer_pidfd_len = sizeof(fd_peer_pidfd);
+	int ret = getsockopt(fd, 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");
+		return -1;
+	}
+	return fd_peer_pidfd;
+}
+
+static bool get_pidfd_info(int fd_peer_pidfd, struct pidfd_info *info)
+{
+	memset(info, 0, sizeof(*info));
+	info->mask = PIDFD_INFO_EXIT | PIDFD_INFO_COREDUMP;
+	return ioctl(fd_peer_pidfd, PIDFD_GET_INFO, info) == 0;
+}
+
+static void
+wait_and_check_coredump_server(pid_t pid_coredump_server,
+			       struct __test_metadata *const _metadata,
+			       FIXTURE_DATA(coredump)* self)
+{
+	int status;
+	waitpid(pid_coredump_server, &status, 0);
+	self->pid_coredump_server = -ESRCH;
+	ASSERT_TRUE(WIFEXITED(status));
+	ASSERT_EQ(WEXITSTATUS(status), 0);
+}
+
 TEST_F(coredump, socket)
 {
-	int fd, pidfd, ret, status;
-	FILE *file;
+	int pidfd, ret, status;
 	pid_t pid, pid_coredump_server;
 	struct stat st;
-	char core_file[PATH_MAX];
 	struct pidfd_info info = {};
 	int ipc_sockets[2];
 	char c;
-	const struct sockaddr_un coredump_sk = {
-		.sun_family = AF_UNIX,
-		.sun_path = "/tmp/coredump.socket",
-	};
-	size_t coredump_sk_len = offsetof(struct sockaddr_un, sun_path) +
-				 sizeof("/tmp/coredump.socket");
+
+	ASSERT_TRUE(set_core_pattern("@/tmp/coredump.socket"));
 
 	ret = socketpair(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0, ipc_sockets);
 	ASSERT_EQ(ret, 0);
 
-	file = fopen("/proc/sys/kernel/core_pattern", "w");
-	ASSERT_NE(file, NULL);
-
-	ret = fprintf(file, "@/tmp/coredump.socket");
-	ASSERT_EQ(ret, strlen("@/tmp/coredump.socket"));
-	ASSERT_EQ(fclose(file), 0);
-
 	pid_coredump_server = fork();
 	ASSERT_GE(pid_coredump_server, 0);
 	if (pid_coredump_server == 0) {
-		int fd_server, fd_coredump, fd_peer_pidfd, fd_core_file;
-		socklen_t fd_peer_pidfd_len;
+		int fd_server = -1, fd_coredump = -1, fd_peer_pidfd = -1, fd_core_file = -1;
+		int exit_code = EXIT_FAILURE;
 
 		close(ipc_sockets[0]);
 
-		fd_server = socket(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0);
+		fd_server = create_and_listen_unix_socket("/tmp/coredump.socket");
 		if (fd_server < 0)
-			_exit(EXIT_FAILURE);
-
-		ret = bind(fd_server, (const struct sockaddr *)&coredump_sk, coredump_sk_len);
-		if (ret < 0) {
-			fprintf(stderr, "Failed to bind coredump socket\n");
-			close(fd_server);
-			close(ipc_sockets[1]);
-			_exit(EXIT_FAILURE);
-		}
-
-		ret = listen(fd_server, 1);
-		if (ret < 0) {
-			fprintf(stderr, "Failed to listen on coredump socket\n");
-			close(fd_server);
-			close(ipc_sockets[1]);
-			_exit(EXIT_FAILURE);
-		}
+			goto out;
 
-		if (write_nointr(ipc_sockets[1], "1", 1) < 0) {
-			close(fd_server);
-			close(ipc_sockets[1]);
-			_exit(EXIT_FAILURE);
-		}
+		if (write_nointr(ipc_sockets[1], "1", 1) < 0)
+			goto out;
 
 		close(ipc_sockets[1]);
 
 		fd_coredump = accept4(fd_server, NULL, NULL, SOCK_CLOEXEC);
-		if (fd_coredump < 0) {
-			fprintf(stderr, "Failed to accept coredump socket connection\n");
-			close(fd_server);
-			_exit(EXIT_FAILURE);
-		}
+		if (fd_coredump < 0)
+			goto out;
 
-		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_server);
-			_exit(EXIT_FAILURE);
-		}
+		fd_peer_pidfd = get_peer_pidfd(fd_coredump);
+		if (fd_peer_pidfd < 0)
+			goto out;
 
-		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_server);
-			close(fd_peer_pidfd);
-			_exit(EXIT_FAILURE);
-		}
+		if (!get_pidfd_info(fd_peer_pidfd, &info))
+			goto out;
 
-		if (!(info.mask & PIDFD_INFO_COREDUMP)) {
-			fprintf(stderr, "Missing coredump information from coredumping task\n");
-			close(fd_coredump);
-			close(fd_server);
-			close(fd_peer_pidfd);
-			_exit(EXIT_FAILURE);
-		}
+		if (!(info.mask & PIDFD_INFO_COREDUMP))
+			goto out;
 
-		if (!(info.coredump_mask & PIDFD_COREDUMPED)) {
-			fprintf(stderr, "Received connection from non-coredumping task\n");
-			close(fd_coredump);
-			close(fd_server);
-			close(fd_peer_pidfd);
-			_exit(EXIT_FAILURE);
-		}
+		if (!(info.coredump_mask & PIDFD_COREDUMPED))
+			goto out;
 
 		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_server);
-			close(fd_peer_pidfd);
-			_exit(EXIT_FAILURE);
-		}
+		if (fd_core_file < 0)
+			goto out;
 
 		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_server);
-				close(fd_peer_pidfd);
-				close(fd_core_file);
-				_exit(EXIT_FAILURE);
-			}
+			if (bytes_read < 0)
+				goto out;
 
 			if (bytes_read == 0)
 				break;
 
 			bytes_write = write(fd_core_file, buffer, bytes_read);
-			if (bytes_read != bytes_write) {
-				close(fd_coredump);
-				close(fd_server);
-				close(fd_peer_pidfd);
-				close(fd_core_file);
-				_exit(EXIT_FAILURE);
-			}
+			if (bytes_read != bytes_write)
+				goto out;
 		}
 
-		close(fd_coredump);
-		close(fd_server);
-		close(fd_peer_pidfd);
-		close(fd_core_file);
-		_exit(EXIT_SUCCESS);
+		exit_code = EXIT_SUCCESS;
+out:
+		if (fd_core_file >= 0)
+			close(fd_core_file);
+		if (fd_peer_pidfd >= 0)
+			close(fd_peer_pidfd);
+		if (fd_coredump >= 0)
+			close(fd_coredump);
+		if (fd_server >= 0)
+			close(fd_server);
+		_exit(exit_code);
 	}
 	self->pid_coredump_server = pid_coredump_server;
 
@@ -335,48 +387,27 @@ TEST_F(coredump, socket)
 	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_TRUE(get_pidfd_info(pidfd, &info));
 	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);
+	wait_and_check_coredump_server(pid_coredump_server, _metadata, self);
 
 	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_detect_userspace_client)
 {
-	int fd, pidfd, ret, status;
-	FILE *file;
+	int pidfd, ret, status;
 	pid_t pid, pid_coredump_server;
 	struct stat st;
-	char core_file[PATH_MAX];
 	struct pidfd_info info = {};
 	int ipc_sockets[2];
 	char c;
-	const struct sockaddr_un coredump_sk = {
-		.sun_family = AF_UNIX,
-		.sun_path = "/tmp/coredump.socket",
-	};
-	size_t coredump_sk_len = offsetof(struct sockaddr_un, sun_path) +
-				 sizeof("/tmp/coredump.socket");
-
-	file = fopen("/proc/sys/kernel/core_pattern", "w");
-	ASSERT_NE(file, NULL);
 
-	ret = fprintf(file, "@/tmp/coredump.socket");
-	ASSERT_EQ(ret, strlen("@/tmp/coredump.socket"));
-	ASSERT_EQ(fclose(file), 0);
+	ASSERT_TRUE(set_core_pattern("@/tmp/coredump.socket"));
 
 	ret = socketpair(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0, ipc_sockets);
 	ASSERT_EQ(ret, 0);
@@ -384,88 +415,49 @@ TEST_F(coredump, socket_detect_userspace_client)
 	pid_coredump_server = fork();
 	ASSERT_GE(pid_coredump_server, 0);
 	if (pid_coredump_server == 0) {
-		int fd_server, fd_coredump, fd_peer_pidfd, fd_core_file;
-		socklen_t fd_peer_pidfd_len;
+		int fd_server = -1, fd_coredump = -1, fd_peer_pidfd = -1;
+		int exit_code = EXIT_FAILURE;
 
 		close(ipc_sockets[0]);
 
-		fd_server = socket(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0);
+		fd_server = create_and_listen_unix_socket("/tmp/coredump.socket");
 		if (fd_server < 0)
-			_exit(EXIT_FAILURE);
+			goto out;
 
-		ret = bind(fd_server, (const struct sockaddr *)&coredump_sk, coredump_sk_len);
-		if (ret < 0) {
-			fprintf(stderr, "Failed to bind coredump socket\n");
-			close(fd_server);
-			close(ipc_sockets[1]);
-			_exit(EXIT_FAILURE);
-		}
-
-		ret = listen(fd_server, 1);
-		if (ret < 0) {
-			fprintf(stderr, "Failed to listen on coredump socket\n");
-			close(fd_server);
-			close(ipc_sockets[1]);
-			_exit(EXIT_FAILURE);
-		}
-
-		if (write_nointr(ipc_sockets[1], "1", 1) < 0) {
-			close(fd_server);
-			close(ipc_sockets[1]);
-			_exit(EXIT_FAILURE);
-		}
+		if (write_nointr(ipc_sockets[1], "1", 1) < 0)
+			goto out;
 
 		close(ipc_sockets[1]);
 
 		fd_coredump = accept4(fd_server, NULL, NULL, SOCK_CLOEXEC);
-		if (fd_coredump < 0) {
-			fprintf(stderr, "Failed to accept coredump socket connection\n");
-			close(fd_server);
-			_exit(EXIT_FAILURE);
-		}
+		if (fd_coredump < 0)
+			goto out;
 
-		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_server);
-			_exit(EXIT_FAILURE);
-		}
+		fd_peer_pidfd = get_peer_pidfd(fd_coredump);
+		if (fd_peer_pidfd < 0)
+			goto out;
 
-		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_server);
-			close(fd_peer_pidfd);
-			_exit(EXIT_FAILURE);
-		}
+		if (!get_pidfd_info(fd_peer_pidfd, &info))
+			goto out;
 
-		if (!(info.mask & PIDFD_INFO_COREDUMP)) {
-			fprintf(stderr, "Missing coredump information from coredumping task\n");
-			close(fd_coredump);
-			close(fd_server);
-			close(fd_peer_pidfd);
-			_exit(EXIT_FAILURE);
-		}
+		if (!(info.mask & PIDFD_INFO_COREDUMP))
+			goto out;
+
+		if (info.coredump_mask & PIDFD_COREDUMPED)
+			goto out;
 
-		if (info.coredump_mask & PIDFD_COREDUMPED) {
-			fprintf(stderr, "Received unexpected connection from coredumping task\n");
+		if (read(fd_coredump, &c, 1) < 1)
+			goto out;
+
+		exit_code = EXIT_SUCCESS;
+out:
+		if (fd_peer_pidfd >= 0)
+			close(fd_peer_pidfd);
+		if (fd_coredump >= 0)
 			close(fd_coredump);
+		if (fd_server >= 0)
 			close(fd_server);
-			close(fd_peer_pidfd);
-			_exit(EXIT_FAILURE);
-		}
-
-		close(fd_coredump);
-		close(fd_server);
-		close(fd_peer_pidfd);
-		close(fd_core_file);
-		_exit(EXIT_SUCCESS);
+		_exit(exit_code);
 	}
 	self->pid_coredump_server = pid_coredump_server;
 
@@ -478,17 +470,22 @@ TEST_F(coredump, socket_detect_userspace_client)
 	if (pid == 0) {
 		int fd_socket;
 		ssize_t ret;
+		const struct sockaddr_un coredump_sk = {
+			.sun_family = AF_UNIX,
+			.sun_path = "/tmp/coredump.socket",
+		};
+		size_t coredump_sk_len =
+			offsetof(struct sockaddr_un, sun_path) +
+			sizeof("/tmp/coredump.socket");
 
 		fd_socket = socket(AF_UNIX, SOCK_STREAM, 0);
 		if (fd_socket < 0)
 			_exit(EXIT_FAILURE);
 
-
 		ret = connect(fd_socket, (const struct sockaddr *)&coredump_sk, coredump_sk_len);
 		if (ret < 0)
 			_exit(EXIT_FAILURE);
 
-		(void *)write(fd_socket, &(char){ 0 }, 1);
 		close(fd_socket);
 		_exit(EXIT_SUCCESS);
 	}
@@ -500,15 +497,11 @@ TEST_F(coredump, socket_detect_userspace_client)
 	ASSERT_TRUE(WIFEXITED(status));
 	ASSERT_EQ(WEXITSTATUS(status), 0);
 
-	info.mask = PIDFD_INFO_EXIT | PIDFD_INFO_COREDUMP;
-	ASSERT_EQ(ioctl(pidfd, PIDFD_GET_INFO, &info), 0);
+	ASSERT_TRUE(get_pidfd_info(pidfd, &info));
 	ASSERT_GT((info.mask & PIDFD_INFO_COREDUMP), 0);
 	ASSERT_EQ((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);
+	wait_and_check_coredump_server(pid_coredump_server, _metadata, self);
 
 	ASSERT_NE(stat("/tmp/coredump.file", &st), 0);
 	ASSERT_EQ(errno, ENOENT);
@@ -516,17 +509,10 @@ TEST_F(coredump, socket_detect_userspace_client)
 
 TEST_F(coredump, socket_enoent)
 {
-	int pidfd, ret, status;
-	FILE *file;
+	int pidfd, status;
 	pid_t pid;
-	char core_file[PATH_MAX];
-
-	file = fopen("/proc/sys/kernel/core_pattern", "w");
-	ASSERT_NE(file, NULL);
 
-	ret = fprintf(file, "@/tmp/coredump.socket");
-	ASSERT_EQ(ret, strlen("@/tmp/coredump.socket"));
-	ASSERT_EQ(fclose(file), 0);
+	ASSERT_TRUE(set_core_pattern("@/tmp/coredump.socket"));
 
 	pid = fork();
 	ASSERT_GE(pid, 0);
@@ -544,7 +530,6 @@ TEST_F(coredump, socket_enoent)
 TEST_F(coredump, socket_no_listener)
 {
 	int pidfd, ret, status;
-	FILE *file;
 	pid_t pid, pid_coredump_server;
 	int ipc_sockets[2];
 	char c;
@@ -555,45 +540,518 @@ TEST_F(coredump, socket_no_listener)
 	size_t coredump_sk_len = offsetof(struct sockaddr_un, sun_path) +
 				 sizeof("/tmp/coredump.socket");
 
+	ASSERT_TRUE(set_core_pattern("@/tmp/coredump.socket"));
+
 	ret = socketpair(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0, ipc_sockets);
 	ASSERT_EQ(ret, 0);
 
-	file = fopen("/proc/sys/kernel/core_pattern", "w");
-	ASSERT_NE(file, NULL);
-
-	ret = fprintf(file, "@/tmp/coredump.socket");
-	ASSERT_EQ(ret, strlen("@/tmp/coredump.socket"));
-	ASSERT_EQ(fclose(file), 0);
-
 	pid_coredump_server = fork();
 	ASSERT_GE(pid_coredump_server, 0);
 	if (pid_coredump_server == 0) {
-		int fd_server;
-		socklen_t fd_peer_pidfd_len;
+		int fd_server = -1;
+		int exit_code = EXIT_FAILURE;
 
 		close(ipc_sockets[0]);
 
 		fd_server = socket(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0);
 		if (fd_server < 0)
-			_exit(EXIT_FAILURE);
+			goto out;
 
 		ret = bind(fd_server, (const struct sockaddr *)&coredump_sk, coredump_sk_len);
-		if (ret < 0) {
-			fprintf(stderr, "Failed to bind coredump socket\n");
+		if (ret < 0)
+			goto out;
+
+		if (write_nointr(ipc_sockets[1], "1", 1) < 0)
+			goto out;
+
+		exit_code = EXIT_SUCCESS;
+out:
+		if (fd_server >= 0)
 			close(fd_server);
-			close(ipc_sockets[1]);
-			_exit(EXIT_FAILURE);
+		close(ipc_sockets[1]);
+		_exit(exit_code);
+	}
+	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_FALSE(WCOREDUMP(status));
+
+	wait_and_check_coredump_server(pid_coredump_server, _metadata, self);
+}
+
+static ssize_t recv_marker(int fd)
+{
+	enum coredump_mark mark = COREDUMP_MARK_REQACK;
+	ssize_t ret;
+
+	ret = recv(fd, &mark, sizeof(mark), MSG_WAITALL);
+	if (ret != sizeof(mark))
+		return -1;
+
+	switch (mark) {
+	case COREDUMP_MARK_REQACK:
+		fprintf(stderr, "Received marker: ReqAck\n");
+		return COREDUMP_MARK_REQACK;
+	case COREDUMP_MARK_MINSIZE:
+		fprintf(stderr, "Received marker: MinSize\n");
+		return COREDUMP_MARK_MINSIZE;
+	case COREDUMP_MARK_MAXSIZE:
+		fprintf(stderr, "Received marker: MaxSize\n");
+		return COREDUMP_MARK_MAXSIZE;
+	case COREDUMP_MARK_UNSUPPORTED:
+		fprintf(stderr, "Received marker: Unsupported\n");
+		return COREDUMP_MARK_UNSUPPORTED;
+	case COREDUMP_MARK_CONFLICTING:
+		fprintf(stderr, "Received marker: Conflicting\n");
+		return COREDUMP_MARK_CONFLICTING;
+	default:
+		fprintf(stderr, "Received unknown marker: %u\n", mark);
+		break;
+	}
+	return -1;
+}
+
+static bool read_marker(int fd, enum coredump_mark mark)
+{
+	ssize_t ret;
+
+	ret = recv_marker(fd);
+	if (ret < 0)
+		return false;
+	return ret == mark;
+}
+
+static bool read_coredump_req(int fd, struct coredump_req *req)
+{
+	ssize_t ret;
+	size_t field_size, user_size, ack_size, kernel_size, remaining_size;
+
+	memset(req, 0, sizeof(*req));
+	field_size = sizeof(req->size);
+
+	/* Peek the size of the coredump request. */
+	ret = recv(fd, req, field_size, MSG_PEEK | MSG_WAITALL);
+	if (ret != field_size)
+		return false;
+	kernel_size = req->size;
+
+	if (kernel_size < COREDUMP_ACK_SIZE_VER0)
+		return false;
+	if (kernel_size >= PAGE_SIZE)
+		return false;
+
+	/* Use the minimum of user and kernel size to read the full request. */
+	user_size = sizeof(struct coredump_req);
+	ack_size = user_size < kernel_size ? user_size : kernel_size;
+	ret = recv(fd, req, ack_size, MSG_WAITALL);
+	if (ret != ack_size)
+		return false;
+
+	fprintf(stderr, "Read coredump request with size %u and mask 0x%llx\n",
+		req->size, (unsigned long long)req->mask);
+
+	if (user_size > kernel_size)
+		remaining_size = user_size - kernel_size;
+	else
+		remaining_size = kernel_size - user_size;
+
+	if (PAGE_SIZE <= remaining_size)
+		return false;
+
+	/*
+	 * Discard any additional data if the kernel's request was larger than
+	 * what we knew about or cared about.
+	 */
+	if (remaining_size) {
+		char buffer[PAGE_SIZE];
+
+		ret = recv(fd, buffer, sizeof(buffer), MSG_WAITALL);
+		if (ret != remaining_size)
+			return false;
+		fprintf(stderr, "Discarded %zu bytes of data after coredump request\n", remaining_size);
+	}
+
+	return true;
+}
+
+static bool send_coredump_ack(int fd, const struct coredump_req *req,
+			      __u64 mask, size_t size_ack)
+{
+	ssize_t ret;
+	/*
+	 * Wrap struct coredump_ack in a larger struct so we can
+	 * simulate sending to much data to the kernel.
+	 */
+	struct large_ack_for_size_testing {
+		struct coredump_ack ack;
+		char buffer[PAGE_SIZE];
+	} large_ack = {};
+
+	if (!size_ack)
+		size_ack = sizeof(struct coredump_ack) < req->size_ack ?
+				   sizeof(struct coredump_ack) :
+				   req->size_ack;
+	large_ack.ack.mask = mask;
+	large_ack.ack.size = size_ack;
+	ret = send(fd, &large_ack, size_ack, MSG_NOSIGNAL);
+	if (ret != size_ack)
+		return false;
+
+	fprintf(stderr, "Sent coredump ack with size %zu and mask 0x%llx\n",
+		size_ack, (unsigned long long)mask);
+	return true;
+}
+
+static bool check_coredump_req(const struct coredump_req *req, size_t min_size,
+			       __u64 required_mask)
+{
+	if (req->size < min_size)
+		return false;
+	if ((req->mask & required_mask) != required_mask)
+		return false;
+	if (req->mask & ~required_mask)
+		return false;
+	return true;
+}
+
+TEST_F(coredump, socket_request_kernel)
+{
+	int pidfd, ret, status;
+	pid_t pid, pid_coredump_server;
+	struct stat st;
+	struct pidfd_info info = {};
+	int ipc_sockets[2];
+	char c;
+
+	ASSERT_TRUE(set_core_pattern("@@/tmp/coredump.socket"));
+
+	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) {
+		struct coredump_req req = {};
+		int fd_server = -1, fd_coredump = -1, fd_core_file = -1, fd_peer_pidfd = -1;
+		int exit_code = EXIT_FAILURE;
+
+		close(ipc_sockets[0]);
+
+		fd_server = create_and_listen_unix_socket("/tmp/coredump.socket");
+		if (fd_server < 0)
+			goto out;
+
+		if (write_nointr(ipc_sockets[1], "1", 1) < 0)
+			goto out;
+
+		close(ipc_sockets[1]);
+
+		fd_coredump = accept4(fd_server, NULL, NULL, SOCK_CLOEXEC);
+		if (fd_coredump < 0)
+			goto out;
+
+		fd_peer_pidfd = get_peer_pidfd(fd_coredump);
+		if (fd_peer_pidfd < 0)
+			goto out;
+
+		if (!get_pidfd_info(fd_peer_pidfd, &info))
+			goto out;
+
+		if (!(info.mask & PIDFD_INFO_COREDUMP))
+			goto out;
+
+		if (!(info.coredump_mask & PIDFD_COREDUMPED))
+			goto out;
+
+		fd_core_file = creat("/tmp/coredump.file", 0644);
+		if (fd_core_file < 0)
+			goto out;
+
+		if (!read_coredump_req(fd_coredump, &req))
+			goto out;
+
+		if (!check_coredump_req(&req, COREDUMP_ACK_SIZE_VER0,
+					COREDUMP_KERNEL | COREDUMP_USERSPACE |
+					COREDUMP_REJECT | COREDUMP_WAIT))
+			goto out;
+
+		if (!send_coredump_ack(fd_coredump, &req,
+				       COREDUMP_KERNEL | COREDUMP_WAIT, 0))
+			goto out;
+
+		if (!read_marker(fd_coredump, COREDUMP_MARK_REQACK))
+			goto out;
+
+		for (;;) {
+			char buffer[4096];
+			ssize_t bytes_read, bytes_write;
+
+			bytes_read = read(fd_coredump, buffer, sizeof(buffer));
+			if (bytes_read < 0)
+				goto out;
+
+			if (bytes_read == 0)
+				break;
+
+			bytes_write = write(fd_core_file, buffer, bytes_read);
+			if (bytes_read != bytes_write)
+				goto out;
 		}
 
-		if (write_nointr(ipc_sockets[1], "1", 1) < 0) {
+		exit_code = EXIT_SUCCESS;
+out:
+		if (fd_core_file >= 0)
+			close(fd_core_file);
+		if (fd_peer_pidfd >= 0)
+			close(fd_peer_pidfd);
+		if (fd_coredump >= 0)
+			close(fd_coredump);
+		if (fd_server >= 0)
 			close(fd_server);
-			close(ipc_sockets[1]);
-			_exit(EXIT_FAILURE);
+		_exit(exit_code);
+	}
+	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));
+
+	ASSERT_TRUE(get_pidfd_info(pidfd, &info));
+	ASSERT_GT((info.mask & PIDFD_INFO_COREDUMP), 0);
+	ASSERT_GT((info.coredump_mask & PIDFD_COREDUMPED), 0);
+
+	wait_and_check_coredump_server(pid_coredump_server, _metadata, self);
+
+	ASSERT_EQ(stat("/tmp/coredump.file", &st), 0);
+	ASSERT_GT(st.st_size, 0);
+	system("file /tmp/coredump.file");
+}
+
+TEST_F(coredump, socket_request_userspace)
+{
+	int pidfd, ret, status;
+	pid_t pid, pid_coredump_server;
+	struct pidfd_info info = {};
+	int ipc_sockets[2];
+	char c;
+
+	ASSERT_TRUE(set_core_pattern("@@/tmp/coredump.socket"));
+
+	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) {
+		struct coredump_req req = {};
+		int fd_server = -1, fd_coredump = -1, fd_peer_pidfd = -1;
+		int exit_code = EXIT_FAILURE;
+
+		close(ipc_sockets[0]);
+
+		fd_server = create_and_listen_unix_socket("/tmp/coredump.socket");
+		if (fd_server < 0)
+			goto out;
+
+		if (write_nointr(ipc_sockets[1], "1", 1) < 0)
+			goto out;
+
+		close(ipc_sockets[1]);
+
+		fd_coredump = accept4(fd_server, NULL, NULL, SOCK_CLOEXEC);
+		if (fd_coredump < 0)
+			goto out;
+
+		fd_peer_pidfd = get_peer_pidfd(fd_coredump);
+		if (fd_peer_pidfd < 0)
+			goto out;
+
+		if (!get_pidfd_info(fd_peer_pidfd, &info))
+			goto out;
+
+		if (!(info.mask & PIDFD_INFO_COREDUMP))
+			goto out;
+
+		if (!(info.coredump_mask & PIDFD_COREDUMPED))
+			goto out;
+
+		if (!read_coredump_req(fd_coredump, &req))
+			goto out;
+
+		if (!check_coredump_req(&req, COREDUMP_ACK_SIZE_VER0,
+					COREDUMP_KERNEL | COREDUMP_USERSPACE |
+					COREDUMP_REJECT | COREDUMP_WAIT))
+			goto out;
+
+		if (!send_coredump_ack(fd_coredump, &req,
+				       COREDUMP_USERSPACE | COREDUMP_WAIT, 0))
+			goto out;
+
+		if (!read_marker(fd_coredump, COREDUMP_MARK_REQACK))
+			goto out;
+
+		for (;;) {
+			char buffer[4096];
+			ssize_t bytes_read;
+
+			bytes_read = read(fd_coredump, buffer, sizeof(buffer));
+			if (bytes_read > 0)
+				goto out;
+
+			if (bytes_read < 0)
+				goto out;
+
+			if (bytes_read == 0)
+				break;
 		}
 
-		close(fd_server);
+		exit_code = EXIT_SUCCESS;
+out:
+		if (fd_peer_pidfd >= 0)
+			close(fd_peer_pidfd);
+		if (fd_coredump >= 0)
+			close(fd_coredump);
+		if (fd_server >= 0)
+			close(fd_server);
+		_exit(exit_code);
+	}
+	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));
+
+	ASSERT_TRUE(get_pidfd_info(pidfd, &info));
+	ASSERT_GT((info.mask & PIDFD_INFO_COREDUMP), 0);
+	ASSERT_GT((info.coredump_mask & PIDFD_COREDUMPED), 0);
+
+	wait_and_check_coredump_server(pid_coredump_server, _metadata, self);
+}
+
+TEST_F(coredump, socket_request_reject)
+{
+	int pidfd, ret, status;
+	pid_t pid, pid_coredump_server;
+	struct pidfd_info info = {};
+	int ipc_sockets[2];
+	char c;
+
+	ASSERT_TRUE(set_core_pattern("@@/tmp/coredump.socket"));
+
+	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) {
+		struct coredump_req req = {};
+		int fd_server = -1, fd_coredump = -1, fd_peer_pidfd = -1;
+		int exit_code = EXIT_FAILURE;
+
+		close(ipc_sockets[0]);
+
+		fd_server = create_and_listen_unix_socket("/tmp/coredump.socket");
+		if (fd_server < 0)
+			goto out;
+
+		if (write_nointr(ipc_sockets[1], "1", 1) < 0)
+			goto out;
+
 		close(ipc_sockets[1]);
-		_exit(EXIT_SUCCESS);
+
+		fd_coredump = accept4(fd_server, NULL, NULL, SOCK_CLOEXEC);
+		if (fd_coredump < 0)
+			goto out;
+
+		fd_peer_pidfd = get_peer_pidfd(fd_coredump);
+		if (fd_peer_pidfd < 0)
+			goto out;
+
+		if (!get_pidfd_info(fd_peer_pidfd, &info))
+			goto out;
+
+		if (!(info.mask & PIDFD_INFO_COREDUMP))
+			goto out;
+
+		if (!(info.coredump_mask & PIDFD_COREDUMPED))
+			goto out;
+
+		if (!read_coredump_req(fd_coredump, &req))
+			goto out;
+
+		if (!check_coredump_req(&req, COREDUMP_ACK_SIZE_VER0,
+					COREDUMP_KERNEL | COREDUMP_USERSPACE |
+					COREDUMP_REJECT | COREDUMP_WAIT))
+			goto out;
+
+		if (!send_coredump_ack(fd_coredump, &req,
+				       COREDUMP_REJECT | COREDUMP_WAIT, 0))
+			goto out;
+
+		if (!read_marker(fd_coredump, COREDUMP_MARK_REQACK))
+			goto out;
+
+		for (;;) {
+			char buffer[4096];
+			ssize_t bytes_read;
+
+			bytes_read = read(fd_coredump, buffer, sizeof(buffer));
+			if (bytes_read > 0)
+				goto out;
+
+			if (bytes_read < 0)
+				goto out;
+
+			if (bytes_read == 0)
+				break;
+		}
+
+		exit_code = EXIT_SUCCESS;
+out:
+		if (fd_peer_pidfd >= 0)
+			close(fd_peer_pidfd);
+		if (fd_coredump >= 0)
+			close(fd_coredump);
+		if (fd_server >= 0)
+			close(fd_server);
+		_exit(exit_code);
 	}
 	self->pid_coredump_server = pid_coredump_server;
 
@@ -613,10 +1071,760 @@ TEST_F(coredump, socket_no_listener)
 	ASSERT_TRUE(WIFSIGNALED(status));
 	ASSERT_FALSE(WCOREDUMP(status));
 
-	waitpid(pid_coredump_server, &status, 0);
-	self->pid_coredump_server = -ESRCH;
-	ASSERT_TRUE(WIFEXITED(status));
-	ASSERT_EQ(WEXITSTATUS(status), 0);
+	ASSERT_TRUE(get_pidfd_info(pidfd, &info));
+	ASSERT_GT((info.mask & PIDFD_INFO_COREDUMP), 0);
+	ASSERT_GT((info.coredump_mask & PIDFD_COREDUMPED), 0);
+
+	wait_and_check_coredump_server(pid_coredump_server, _metadata, self);
+}
+
+TEST_F(coredump, socket_request_invalid_flag_combination)
+{
+	int pidfd, ret, status;
+	pid_t pid, pid_coredump_server;
+	struct pidfd_info info = {};
+	int ipc_sockets[2];
+	char c;
+
+	ASSERT_TRUE(set_core_pattern("@@/tmp/coredump.socket"));
+
+	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) {
+		struct coredump_req req = {};
+		int fd_server = -1, fd_coredump = -1, fd_peer_pidfd = -1;
+		int exit_code = EXIT_FAILURE;
+
+		close(ipc_sockets[0]);
+
+		fd_server = create_and_listen_unix_socket("/tmp/coredump.socket");
+		if (fd_server < 0)
+			goto out;
+
+		if (write_nointr(ipc_sockets[1], "1", 1) < 0)
+			goto out;
+
+		close(ipc_sockets[1]);
+
+		fd_coredump = accept4(fd_server, NULL, NULL, SOCK_CLOEXEC);
+		if (fd_coredump < 0)
+			goto out;
+
+		fd_peer_pidfd = get_peer_pidfd(fd_coredump);
+		if (fd_peer_pidfd < 0)
+			goto out;
+
+		if (!get_pidfd_info(fd_peer_pidfd, &info))
+			goto out;
+
+		if (!(info.mask & PIDFD_INFO_COREDUMP))
+			goto out;
+
+		if (!(info.coredump_mask & PIDFD_COREDUMPED))
+			goto out;
+
+		if (!read_coredump_req(fd_coredump, &req))
+			goto out;
+
+		if (!check_coredump_req(&req, COREDUMP_ACK_SIZE_VER0,
+					COREDUMP_KERNEL | COREDUMP_USERSPACE |
+					COREDUMP_REJECT | COREDUMP_WAIT))
+			goto out;
+
+		if (!send_coredump_ack(fd_coredump, &req,
+				       COREDUMP_KERNEL | COREDUMP_REJECT | COREDUMP_WAIT, 0))
+			goto out;
+
+		if (!read_marker(fd_coredump, COREDUMP_MARK_CONFLICTING))
+			goto out;
+
+		exit_code = EXIT_SUCCESS;
+out:
+		if (fd_peer_pidfd >= 0)
+			close(fd_peer_pidfd);
+		if (fd_coredump >= 0)
+			close(fd_coredump);
+		if (fd_server >= 0)
+			close(fd_server);
+		_exit(exit_code);
+	}
+	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_FALSE(WCOREDUMP(status));
+
+	ASSERT_TRUE(get_pidfd_info(pidfd, &info));
+	ASSERT_GT((info.mask & PIDFD_INFO_COREDUMP), 0);
+	ASSERT_GT((info.coredump_mask & PIDFD_COREDUMPED), 0);
+
+	wait_and_check_coredump_server(pid_coredump_server, _metadata, self);
+}
+
+TEST_F(coredump, socket_request_unknown_flag)
+{
+	int pidfd, ret, status;
+	pid_t pid, pid_coredump_server;
+	struct pidfd_info info = {};
+	int ipc_sockets[2];
+	char c;
+
+	ASSERT_TRUE(set_core_pattern("@@/tmp/coredump.socket"));
+
+	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) {
+		struct coredump_req req = {};
+		int fd_server = -1, fd_coredump = -1, fd_peer_pidfd = -1;
+		int exit_code = EXIT_FAILURE;
+
+		close(ipc_sockets[0]);
+
+		fd_server = create_and_listen_unix_socket("/tmp/coredump.socket");
+		if (fd_server < 0)
+			goto out;
+
+		if (write_nointr(ipc_sockets[1], "1", 1) < 0)
+			goto out;
+
+		close(ipc_sockets[1]);
+
+		fd_coredump = accept4(fd_server, NULL, NULL, SOCK_CLOEXEC);
+		if (fd_coredump < 0)
+			goto out;
+
+		fd_peer_pidfd = get_peer_pidfd(fd_coredump);
+		if (fd_peer_pidfd < 0)
+			goto out;
+
+		if (!get_pidfd_info(fd_peer_pidfd, &info))
+			goto out;
+
+		if (!(info.mask & PIDFD_INFO_COREDUMP))
+			goto out;
+
+		if (!(info.coredump_mask & PIDFD_COREDUMPED))
+			goto out;
+
+		if (!read_coredump_req(fd_coredump, &req))
+			goto out;
+
+		if (!check_coredump_req(&req, COREDUMP_ACK_SIZE_VER0,
+					COREDUMP_KERNEL | COREDUMP_USERSPACE |
+					COREDUMP_REJECT | COREDUMP_WAIT))
+			goto out;
+
+		if (!send_coredump_ack(fd_coredump, &req, (1ULL << 63), 0))
+			goto out;
+
+		if (!read_marker(fd_coredump, COREDUMP_MARK_UNSUPPORTED))
+			goto out;
+
+		exit_code = EXIT_SUCCESS;
+out:
+		if (fd_peer_pidfd >= 0)
+			close(fd_peer_pidfd);
+		if (fd_coredump >= 0)
+			close(fd_coredump);
+		if (fd_server >= 0)
+			close(fd_server);
+		_exit(exit_code);
+	}
+	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_FALSE(WCOREDUMP(status));
+
+	ASSERT_TRUE(get_pidfd_info(pidfd, &info));
+	ASSERT_GT((info.mask & PIDFD_INFO_COREDUMP), 0);
+	ASSERT_GT((info.coredump_mask & PIDFD_COREDUMPED), 0);
+
+	wait_and_check_coredump_server(pid_coredump_server, _metadata, self);
+}
+
+TEST_F(coredump, socket_request_invalid_size_small)
+{
+	int pidfd, ret, status;
+	pid_t pid, pid_coredump_server;
+	struct pidfd_info info = {};
+	int ipc_sockets[2];
+	char c;
+
+	ASSERT_TRUE(set_core_pattern("@@/tmp/coredump.socket"));
+
+	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) {
+		struct coredump_req req = {};
+		int fd_server = -1, fd_coredump = -1, fd_peer_pidfd = -1;
+		int exit_code = EXIT_FAILURE;
+
+		close(ipc_sockets[0]);
+
+		fd_server = create_and_listen_unix_socket("/tmp/coredump.socket");
+		if (fd_server < 0)
+			goto out;
+
+		if (write_nointr(ipc_sockets[1], "1", 1) < 0)
+			goto out;
+
+		close(ipc_sockets[1]);
+
+		fd_coredump = accept4(fd_server, NULL, NULL, SOCK_CLOEXEC);
+		if (fd_coredump < 0)
+			goto out;
+
+		fd_peer_pidfd = get_peer_pidfd(fd_coredump);
+		if (fd_peer_pidfd < 0)
+			goto out;
+
+		if (!get_pidfd_info(fd_peer_pidfd, &info))
+			goto out;
+
+		if (!(info.mask & PIDFD_INFO_COREDUMP))
+			goto out;
+
+		if (!(info.coredump_mask & PIDFD_COREDUMPED))
+			goto out;
+
+		if (!read_coredump_req(fd_coredump, &req))
+			goto out;
+
+		if (!check_coredump_req(&req, COREDUMP_ACK_SIZE_VER0,
+					COREDUMP_KERNEL | COREDUMP_USERSPACE |
+					COREDUMP_REJECT | COREDUMP_WAIT))
+			goto out;
+
+		if (!send_coredump_ack(fd_coredump, &req,
+				       COREDUMP_REJECT | COREDUMP_WAIT,
+				       COREDUMP_ACK_SIZE_VER0 / 2))
+			goto out;
+
+		if (!read_marker(fd_coredump, COREDUMP_MARK_MINSIZE))
+			goto out;
+
+		exit_code = EXIT_SUCCESS;
+out:
+		if (fd_peer_pidfd >= 0)
+			close(fd_peer_pidfd);
+		if (fd_coredump >= 0)
+			close(fd_coredump);
+		if (fd_server >= 0)
+			close(fd_server);
+		_exit(exit_code);
+	}
+	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_FALSE(WCOREDUMP(status));
+
+	ASSERT_TRUE(get_pidfd_info(pidfd, &info));
+	ASSERT_GT((info.mask & PIDFD_INFO_COREDUMP), 0);
+	ASSERT_GT((info.coredump_mask & PIDFD_COREDUMPED), 0);
+
+	wait_and_check_coredump_server(pid_coredump_server, _metadata, self);
+}
+
+TEST_F(coredump, socket_request_invalid_size_large)
+{
+	int pidfd, ret, status;
+	pid_t pid, pid_coredump_server;
+	struct pidfd_info info = {};
+	int ipc_sockets[2];
+	char c;
+
+	ASSERT_TRUE(set_core_pattern("@@/tmp/coredump.socket"));
+
+	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) {
+		struct coredump_req req = {};
+		int fd_server = -1, fd_coredump = -1, fd_peer_pidfd = -1;
+		int exit_code = EXIT_FAILURE;
+
+		close(ipc_sockets[0]);
+
+		fd_server = create_and_listen_unix_socket("/tmp/coredump.socket");
+		if (fd_server < 0)
+			goto out;
+
+		if (write_nointr(ipc_sockets[1], "1", 1) < 0)
+			goto out;
+
+		close(ipc_sockets[1]);
+
+		fd_coredump = accept4(fd_server, NULL, NULL, SOCK_CLOEXEC);
+		if (fd_coredump < 0)
+			goto out;
+
+		fd_peer_pidfd = get_peer_pidfd(fd_coredump);
+		if (fd_peer_pidfd < 0)
+			goto out;
+
+		if (!get_pidfd_info(fd_peer_pidfd, &info))
+			goto out;
+
+		if (!(info.mask & PIDFD_INFO_COREDUMP))
+			goto out;
+
+		if (!(info.coredump_mask & PIDFD_COREDUMPED))
+			goto out;
+
+		if (!read_coredump_req(fd_coredump, &req))
+			goto out;
+
+		if (!check_coredump_req(&req, COREDUMP_ACK_SIZE_VER0,
+					COREDUMP_KERNEL | COREDUMP_USERSPACE |
+					COREDUMP_REJECT | COREDUMP_WAIT))
+			goto out;
+
+		if (!send_coredump_ack(fd_coredump, &req,
+				       COREDUMP_REJECT | COREDUMP_WAIT,
+				       COREDUMP_ACK_SIZE_VER0 + PAGE_SIZE))
+			goto out;
+
+		if (!read_marker(fd_coredump, COREDUMP_MARK_MAXSIZE))
+			goto out;
+
+		exit_code = EXIT_SUCCESS;
+out:
+		if (fd_peer_pidfd >= 0)
+			close(fd_peer_pidfd);
+		if (fd_coredump >= 0)
+			close(fd_coredump);
+		if (fd_server >= 0)
+			close(fd_server);
+		_exit(exit_code);
+	}
+	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_FALSE(WCOREDUMP(status));
+
+	ASSERT_TRUE(get_pidfd_info(pidfd, &info));
+	ASSERT_GT((info.mask & PIDFD_INFO_COREDUMP), 0);
+	ASSERT_GT((info.coredump_mask & PIDFD_COREDUMPED), 0);
+
+	wait_and_check_coredump_server(pid_coredump_server, _metadata, self);
+}
+
+static int open_coredump_tmpfile(int fd_tmpfs_detached)
+{
+	return openat(fd_tmpfs_detached, ".", O_TMPFILE | O_RDWR | O_EXCL, 0600);
+}
+
+#define NUM_CRASHING_COREDUMPS 5
+
+TEST_F_TIMEOUT(coredump, socket_multiple_crashing_coredumps, 500)
+{
+	int pidfd[NUM_CRASHING_COREDUMPS], status[NUM_CRASHING_COREDUMPS];
+	pid_t pid[NUM_CRASHING_COREDUMPS], pid_coredump_server;
+	struct pidfd_info info = {};
+	int ipc_sockets[2];
+	char c;
+
+	ASSERT_TRUE(set_core_pattern("@@/tmp/coredump.socket"));
+
+	ASSERT_EQ(socketpair(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0, ipc_sockets), 0);
+
+	pid_coredump_server = fork();
+	ASSERT_GE(pid_coredump_server, 0);
+	if (pid_coredump_server == 0) {
+		int fd_server = -1, fd_coredump = -1, fd_peer_pidfd = -1, fd_core_file = -1;
+		int exit_code = EXIT_FAILURE;
+		struct coredump_req req = {};
+
+		close(ipc_sockets[0]);
+		fd_server = create_and_listen_unix_socket("/tmp/coredump.socket");
+		if (fd_server < 0) {
+			fprintf(stderr, "Failed to create and listen on unix socket\n");
+			goto out;
+		}
+
+		if (write_nointr(ipc_sockets[1], "1", 1) < 0) {
+			fprintf(stderr, "Failed to notify parent via ipc socket\n");
+			goto out;
+		}
+		close(ipc_sockets[1]);
+
+		for (int i = 0; i < NUM_CRASHING_COREDUMPS; i++) {
+			fd_coredump = accept4(fd_server, NULL, NULL, SOCK_CLOEXEC);
+			if (fd_coredump < 0) {
+				fprintf(stderr, "accept4 failed: %m\n");
+				goto out;
+			}
+
+			fd_peer_pidfd = get_peer_pidfd(fd_coredump);
+			if (fd_peer_pidfd < 0) {
+				fprintf(stderr, "get_peer_pidfd failed for fd %d: %m\n", fd_coredump);
+				goto out;
+			}
+
+			if (!get_pidfd_info(fd_peer_pidfd, &info)) {
+				fprintf(stderr, "get_pidfd_info failed for fd %d\n", fd_peer_pidfd);
+				goto out;
+			}
+
+			if (!(info.mask & PIDFD_INFO_COREDUMP)) {
+				fprintf(stderr, "pidfd info missing PIDFD_INFO_COREDUMP for fd %d\n", fd_peer_pidfd);
+				goto out;
+			}
+			if (!(info.coredump_mask & PIDFD_COREDUMPED)) {
+				fprintf(stderr, "pidfd info missing PIDFD_COREDUMPED for fd %d\n", fd_peer_pidfd);
+				goto out;
+			}
+
+			if (!read_coredump_req(fd_coredump, &req)) {
+				fprintf(stderr, "read_coredump_req failed for fd %d\n", fd_coredump);
+				goto out;
+			}
+
+			if (!check_coredump_req(&req, COREDUMP_ACK_SIZE_VER0,
+						COREDUMP_KERNEL | COREDUMP_USERSPACE |
+						COREDUMP_REJECT | COREDUMP_WAIT)) {
+				fprintf(stderr, "check_coredump_req failed for fd %d\n", fd_coredump);
+				goto out;
+			}
+
+			if (!send_coredump_ack(fd_coredump, &req,
+					       COREDUMP_KERNEL | COREDUMP_WAIT, 0)) {
+				fprintf(stderr, "send_coredump_ack failed for fd %d\n", fd_coredump);
+				goto out;
+			}
+
+			if (!read_marker(fd_coredump, COREDUMP_MARK_REQACK)) {
+				fprintf(stderr, "read_marker failed for fd %d\n", fd_coredump);
+				goto out;
+			}
+
+			fd_core_file = open_coredump_tmpfile(self->fd_tmpfs_detached);
+			if (fd_core_file < 0) {
+				fprintf(stderr, "%m - open_coredump_tmpfile failed for fd %d\n", fd_coredump);
+				goto out;
+			}
+
+			for (;;) {
+				char buffer[4096];
+				ssize_t bytes_read, bytes_write;
+
+				bytes_read = read(fd_coredump, buffer, sizeof(buffer));
+				if (bytes_read < 0) {
+					fprintf(stderr, "read failed for fd %d: %m\n", fd_coredump);
+					goto out;
+				}
+
+				if (bytes_read == 0)
+					break;
+
+				bytes_write = write(fd_core_file, buffer, bytes_read);
+				if (bytes_read != bytes_write) {
+					fprintf(stderr, "write failed for fd %d: %m\n", fd_core_file);
+					goto out;
+				}
+			}
+
+			close(fd_core_file);
+			close(fd_peer_pidfd);
+			close(fd_coredump);
+			fd_peer_pidfd = -1;
+			fd_coredump = -1;
+		}
+
+		exit_code = EXIT_SUCCESS;
+out:
+		if (fd_core_file >= 0)
+			close(fd_core_file);
+		if (fd_peer_pidfd >= 0)
+			close(fd_peer_pidfd);
+		if (fd_coredump >= 0)
+			close(fd_coredump);
+		if (fd_server >= 0)
+			close(fd_server);
+		_exit(exit_code);
+	}
+	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);
+
+	for (int i = 0; i < NUM_CRASHING_COREDUMPS; i++) {
+		pid[i] = fork();
+		ASSERT_GE(pid[i], 0);
+		if (pid[i] == 0)
+			crashing_child();
+		pidfd[i] = sys_pidfd_open(pid[i], 0);
+		ASSERT_GE(pidfd[i], 0);
+	}
+
+	for (int i = 0; i < NUM_CRASHING_COREDUMPS; i++) {
+		waitpid(pid[i], &status[i], 0);
+		ASSERT_TRUE(WIFSIGNALED(status[i]));
+		ASSERT_TRUE(WCOREDUMP(status[i]));
+	}
+
+	for (int i = 0; i < NUM_CRASHING_COREDUMPS; i++) {
+		info.mask = PIDFD_INFO_EXIT | PIDFD_INFO_COREDUMP;
+		ASSERT_EQ(ioctl(pidfd[i], PIDFD_GET_INFO, &info), 0);
+		ASSERT_GT((info.mask & PIDFD_INFO_COREDUMP), 0);
+		ASSERT_GT((info.coredump_mask & PIDFD_COREDUMPED), 0);
+	}
+
+	wait_and_check_coredump_server(pid_coredump_server, _metadata, self);
+}
+
+#define MAX_EVENTS 128
+
+static void process_coredump_worker(int fd_coredump, int fd_peer_pidfd, int fd_core_file)
+{
+	int epfd = -1;
+	int exit_code = EXIT_FAILURE;
+
+	epfd = epoll_create1(0);
+	if (epfd < 0)
+		goto out;
+
+	struct epoll_event ev;
+	ev.events = EPOLLIN | EPOLLRDHUP | EPOLLET;
+	ev.data.fd = fd_coredump;
+	if (epoll_ctl(epfd, EPOLL_CTL_ADD, fd_coredump, &ev) < 0)
+		goto out;
+
+	for (;;) {
+		struct epoll_event events[1];
+		int n = epoll_wait(epfd, events, 1, -1);
+		if (n < 0)
+			break;
+
+		if (events[0].events & (EPOLLIN | EPOLLRDHUP)) {
+			for (;;) {
+				char buffer[4096];
+				ssize_t bytes_read = read(fd_coredump, buffer, sizeof(buffer));
+				if (bytes_read < 0) {
+					if (errno == EAGAIN || errno == EWOULDBLOCK)
+						break;
+					goto out;
+				}
+				if (bytes_read == 0)
+					goto done;
+				ssize_t bytes_write = write(fd_core_file, buffer, bytes_read);
+				if (bytes_write != bytes_read)
+					goto out;
+			}
+		}
+	}
+
+done:
+	exit_code = EXIT_SUCCESS;
+out:
+	if (epfd >= 0)
+		close(epfd);
+	if (fd_core_file >= 0)
+		close(fd_core_file);
+	if (fd_peer_pidfd >= 0)
+		close(fd_peer_pidfd);
+	if (fd_coredump >= 0)
+		close(fd_coredump);
+	_exit(exit_code);
+}
+
+TEST_F_TIMEOUT(coredump, socket_multiple_crashing_coredumps_epoll_workers, 500)
+{
+	int pidfd[NUM_CRASHING_COREDUMPS], status[NUM_CRASHING_COREDUMPS];
+	pid_t pid[NUM_CRASHING_COREDUMPS], pid_coredump_server, worker_pids[NUM_CRASHING_COREDUMPS];
+	struct pidfd_info info = {};
+	int ipc_sockets[2];
+	char c;
+
+	ASSERT_TRUE(set_core_pattern("@@/tmp/coredump.socket"));
+	ASSERT_EQ(socketpair(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0, ipc_sockets), 0);
+
+	pid_coredump_server = fork();
+	ASSERT_GE(pid_coredump_server, 0);
+	if (pid_coredump_server == 0) {
+		int fd_server = -1, exit_code = EXIT_FAILURE, n_conns = 0;
+		fd_server = -1;
+		exit_code = EXIT_FAILURE;
+		n_conns = 0;
+		close(ipc_sockets[0]);
+		fd_server = create_and_listen_unix_socket("/tmp/coredump.socket");
+		if (fd_server < 0)
+			goto out;
+
+		if (write_nointr(ipc_sockets[1], "1", 1) < 0)
+			goto out;
+		close(ipc_sockets[1]);
+
+		while (n_conns < NUM_CRASHING_COREDUMPS) {
+			int fd_coredump = -1, fd_peer_pidfd = -1, fd_core_file = -1;
+			struct coredump_req req = {};
+			fd_coredump = accept4(fd_server, NULL, NULL, SOCK_CLOEXEC);
+			if (fd_coredump < 0) {
+				if (errno == EAGAIN || errno == EWOULDBLOCK)
+					continue;
+				goto out;
+			}
+			fd_peer_pidfd = get_peer_pidfd(fd_coredump);
+			if (fd_peer_pidfd < 0)
+				goto out;
+			if (!get_pidfd_info(fd_peer_pidfd, &info))
+				goto out;
+			if (!(info.mask & PIDFD_INFO_COREDUMP) || !(info.coredump_mask & PIDFD_COREDUMPED))
+				goto out;
+			if (!read_coredump_req(fd_coredump, &req))
+				goto out;
+			if (!check_coredump_req(&req, COREDUMP_ACK_SIZE_VER0,
+						COREDUMP_KERNEL | COREDUMP_USERSPACE |
+						COREDUMP_REJECT | COREDUMP_WAIT))
+				goto out;
+			if (!send_coredump_ack(fd_coredump, &req, COREDUMP_KERNEL | COREDUMP_WAIT, 0))
+				goto out;
+			if (!read_marker(fd_coredump, COREDUMP_MARK_REQACK))
+				goto out;
+			fd_core_file = open_coredump_tmpfile(self->fd_tmpfs_detached);
+			if (fd_core_file < 0)
+				goto out;
+			pid_t worker = fork();
+			if (worker == 0) {
+				close(fd_server);
+				process_coredump_worker(fd_coredump, fd_peer_pidfd, fd_core_file);
+			}
+			worker_pids[n_conns] = worker;
+			if (fd_coredump >= 0)
+				close(fd_coredump);
+			if (fd_peer_pidfd >= 0)
+				close(fd_peer_pidfd);
+			if (fd_core_file >= 0)
+				close(fd_core_file);
+			n_conns++;
+		}
+		exit_code = EXIT_SUCCESS;
+out:
+		if (fd_server >= 0)
+			close(fd_server);
+
+		// Reap all worker processes
+		for (int i = 0; i < n_conns; i++) {
+			int wstatus;
+			if (waitpid(worker_pids[i], &wstatus, 0) < 0) {
+				fprintf(stderr, "Failed to wait for worker %d: %m\n", worker_pids[i]);
+			} else if (WIFEXITED(wstatus) && WEXITSTATUS(wstatus) != EXIT_SUCCESS) {
+				fprintf(stderr, "Worker %d exited with error code %d\n", worker_pids[i], WEXITSTATUS(wstatus));
+				exit_code = EXIT_FAILURE;
+			}
+		}
+
+		_exit(exit_code);
+	}
+	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);
+
+	for (int i = 0; i < NUM_CRASHING_COREDUMPS; i++) {
+		pid[i] = fork();
+		ASSERT_GE(pid[i], 0);
+		if (pid[i] == 0)
+			crashing_child();
+		pidfd[i] = sys_pidfd_open(pid[i], 0);
+		ASSERT_GE(pidfd[i], 0);
+	}
+
+	for (int i = 0; i < NUM_CRASHING_COREDUMPS; i++) {
+		ASSERT_GE(waitpid(pid[i], &status[i], 0), 0);
+		ASSERT_TRUE(WIFSIGNALED(status[i]));
+		ASSERT_TRUE(WCOREDUMP(status[i]));
+	}
+
+	for (int i = 0; i < NUM_CRASHING_COREDUMPS; i++) {
+		info.mask = PIDFD_INFO_EXIT | PIDFD_INFO_COREDUMP;
+		ASSERT_EQ(ioctl(pidfd[i], PIDFD_GET_INFO, &info), 0);
+		ASSERT_GT((info.mask & PIDFD_INFO_COREDUMP), 0);
+		ASSERT_GT((info.coredump_mask & PIDFD_COREDUMPED), 0);
+	}
+
+	wait_and_check_coredump_server(pid_coredump_server, _metadata, self);
+}
+
+TEST_F(coredump, socket_invalid_paths)
+{
+	ASSERT_FALSE(set_core_pattern("@ /tmp/coredump.socket"));
+	ASSERT_FALSE(set_core_pattern("@/tmp/../coredump.socket"));
+	ASSERT_FALSE(set_core_pattern("@../coredump.socket"));
+	ASSERT_FALSE(set_core_pattern("@/tmp/coredump.socket/.."));
+	ASSERT_FALSE(set_core_pattern("@.."));
+
+	ASSERT_FALSE(set_core_pattern("@@ /tmp/coredump.socket"));
+	ASSERT_FALSE(set_core_pattern("@@/tmp/../coredump.socket"));
+	ASSERT_FALSE(set_core_pattern("@@../coredump.socket"));
+	ASSERT_FALSE(set_core_pattern("@@/tmp/coredump.socket/.."));
+	ASSERT_FALSE(set_core_pattern("@@.."));
+
+	ASSERT_FALSE(set_core_pattern("@@@/tmp/coredump.socket"));
 }
 
 TEST_HARNESS_MAIN