Merge patch series "coredump: add coredump socket"

Christian Brauner <brauner@kernel.org> says:

Coredumping currently supports two modes:

(1) Dumping directly into a file somewhere on the filesystem.
(2) Dumping into a pipe connected to a usermode helper process
    spawned as a child of the system_unbound_wq or kthreadd.

For simplicity I'm mostly ignoring (1). There's probably still some
users of (1) out there but processing coredumps in this way can be
considered adventurous especially in the face of set*id binaries.

The most common option should be (2) by now. It works by allowing
userspace to put a string into /proc/sys/kernel/core_pattern like:

        |/usr/lib/systemd/systemd-coredump %P %u %g %s %t %c %h

The "|" at the beginning indicates to the kernel that a pipe must be
used. The path following the pipe indicator is a path to a binary that
will be spawned as a usermode helper process. Any additional parameters
pass information about the task that is generating the coredump to the
binary that processes the coredump.

In the example core_pattern shown above systemd-coredump is spawned as a
usermode helper. There's various conceptual consequences of this
(non-exhaustive list):

- systemd-coredump is spawned with file descriptor number 0 (stdin)
  connected to the read-end of the pipe. All other file descriptors are
  closed. That specifically includes 1 (stdout) and 2 (stderr). This has
  already caused bugs because userspace assumed that this cannot happen
  (Whether or not this is a sane assumption is irrelevant.).

- systemd-coredump will be spawned as a child of system_unbound_wq. So
  it is not a child of any userspace process and specifically not a
  child of PID 1. It cannot be waited upon and is in a weird hybrid
  upcall which are difficult for userspace to control correctly.

- systemd-coredump is spawned with full kernel privileges. This
  necessitates all kinds of weird privilege dropping excercises in
  userspace to make this safe.

- A new usermode helper has to be spawned for each crashing process.

This series adds a new mode:

(3) Dumping into an AF_UNIX socket.

Userspace can set /proc/sys/kernel/core_pattern to:

        @/path/to/coredump.socket

The "@" at the beginning indicates to the kernel that an AF_UNIX
coredump socket will be used to process coredumps.

The coredump socket must be located in the initial mount namespace.
When a task coredumps it opens a client socket in the initial network
namespace and connects to the coredump socket.

- The coredump server should use SO_PEERPIDFD to get a stable handle on
  the connected crashing task. The retrieved pidfd will provide a stable
  reference even if the crashing task gets SIGKILLed while generating
  the coredump.

- By setting core_pipe_limit non-zero userspace can guarantee that the
  crashing task cannot be reaped behind it's back and thus process all
  necessary information in /proc/<pid>. The SO_PEERPIDFD can be used to
  detect whether /proc/<pid> still refers to the same process.

  The core_pipe_limit isn't used to rate-limit connections to the
  socket. This can simply be done via AF_UNIX socket directly.

- The pidfd for the crashing task will contain information how the task
  coredumps. The PIDFD_GET_INFO ioctl gained a new flag
  PIDFD_INFO_COREDUMP which can be used to retreive the coredump
  information.

  If the coredump gets a new coredump client connection the kernel
  guarantees that PIDFD_INFO_COREDUMP information is available.
  Currently the following information is provided in the new
  @coredump_mask extension to struct pidfd_info:

  * PIDFD_COREDUMPED is raised if the task did actually coredump.
  * PIDFD_COREDUMP_SKIP	is raised if the task skipped coredumping (e.g.,
    undumpable).
  * PIDFD_COREDUMP_USER	is raised if this is a regular coredump and
    doesn't need special care by the coredump server.
  * PIDFD_COREDUMP_ROOT is raised if the generated coredump should be
    treated as sensitive and the coredump server should restrict access
    to the generated coredump to sufficiently privileged users.

- The coredump server should mark itself as non-dumpable.

- A container coredump server in a separate network namespace can simply
  bind to another well-know address and systemd-coredump fowards
  coredumps to the container.

- Coredumps could in the future also be handled via per-user/session
  coredump servers that run only with that users privileges.

  The coredump server listens on the coredump socket and accepts a
  new coredump connection. It then retrieves SO_PEERPIDFD for the
  client, inspects uid/gid and hands the accepted client to the users
  own coredump handler which runs with the users privileges only
  (It must of coure pay close attention to not forward crashing suid
  binaries.).

The new coredump socket will allow userspace to not have to rely on
usermode helpers for processing coredumps and provides a safer way to
handle them instead of relying on super privileged coredumping helpers.

This will also be significantly more lightweight since no fork()+exec()
for the usermodehelper is required for each crashing process. The
coredump server in userspace can just keep a worker pool.

* patches from https://lore.kernel.org/20250516-work-coredump-socket-v8-0-664f3caf2516@kernel.org:
  selftests/coredump: add tests for AF_UNIX coredumps
  selftests/pidfd: add PIDFD_INFO_COREDUMP infrastructure
  coredump: validate socket name as it is written
  coredump: show supported coredump modes
  pidfs, coredump: add PIDFD_INFO_COREDUMP
  coredump: add coredump socket
  coredump: reflow dump helpers a little
  coredump: massage do_coredump()
  coredump: massage format_corename()

Link: https://lore.kernel.org/20250516-work-coredump-socket-v8-0-664f3caf2516@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>

2 files changed, 488 insertions, 1 deletions

diff --git a/tools/testing/selftests/coredump/stackdump_test.c b/tools/testing/selftests/coredump/stackdump_test.c
index fe3c728cd6be..9984413be9f0 100644
--- a/tools/testing/selftests/coredump/stackdump_test.c
+++ b/tools/testing/selftests/coredump/stackdump_test.c
@@ -1,14 +1,20 @@
 // SPDX-License-Identifier: GPL-2.0
 
 #include <fcntl.h>
+#include <inttypes.h>
 #include <libgen.h>
 #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 +41,7 @@ static void crashing_child(void)
 FIXTURE(coredump)
 {
 	char original_core_pattern[256];
+	pid_t pid_coredump_server;
 };
 
 FIXTURE_SETUP(coredump)
@@ -44,6 +51,7 @@ 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 +69,17 @@ 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);
+	}
+	unlink("/tmp/coredump.file");
+	unlink("/tmp/coredump.socket");
+
 	file = fopen("/proc/sys/kernel/core_pattern", "w");
 	if (!file) {
 		reason = "Unable to open core_pattern";
@@ -154,4 +169,454 @@ 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;
+	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");
+
+	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;
+
+		close(ipc_sockets[0]);
+
+		fd_server = socket(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0);
+		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);
+		}
+
+		if (write_nointr(ipc_sockets[1], "1", 1) < 0) {
+			close(fd_server);
+			close(ipc_sockets[1]);
+			_exit(EXIT_FAILURE);
+		}
+
+		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);
+		}
+
+		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);
+		}
+
+		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 (!(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.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);
+		}
+
+		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);
+		}
+
+		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)
+				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);
+			}
+		}
+
+		close(fd_coredump);
+		close(fd_server);
+		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_detect_userspace_client)
+{
+	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;
+	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);
+
+	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_server, fd_coredump, fd_peer_pidfd, fd_core_file;
+		socklen_t fd_peer_pidfd_len;
+
+		close(ipc_sockets[0]);
+
+		fd_server = socket(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0);
+		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);
+		}
+
+		if (write_nointr(ipc_sockets[1], "1", 1) < 0) {
+			close(fd_server);
+			close(ipc_sockets[1]);
+			_exit(EXIT_FAILURE);
+		}
+
+		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);
+		}
+
+		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);
+		}
+
+		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 (!(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.coredump_mask & PIDFD_COREDUMPED) {
+			fprintf(stderr, "Received unexpected connection from coredumping task\n");
+			close(fd_coredump);
+			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);
+	}
+	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) {
+		int fd_socket;
+		ssize_t ret;
+
+		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);
+	}
+
+	pidfd = sys_pidfd_open(pid, 0);
+	ASSERT_GE(pidfd, 0);
+
+	waitpid(pid, &status, 0);
+	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_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);
+
+	ASSERT_NE(stat("/tmp/coredump.file", &st), 0);
+	ASSERT_EQ(errno, ENOENT);
+}
+
+TEST_F(coredump, socket_enoent)
+{
+	int pidfd, ret, status;
+	FILE *file;
+	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);
+
+	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));
+}
+
+TEST_F(coredump, socket_no_listener)
+{
+	int pidfd, ret, status;
+	FILE *file;
+	pid_t pid, pid_coredump_server;
+	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");
+
+	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;
+
+		close(ipc_sockets[0]);
+
+		fd_server = socket(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0);
+		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);
+		}
+
+		if (write_nointr(ipc_sockets[1], "1", 1) < 0) {
+			close(fd_server);
+			close(ipc_sockets[1]);
+			_exit(EXIT_FAILURE);
+		}
+
+		close(fd_server);
+		close(ipc_sockets[1]);
+		_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_FALSE(WCOREDUMP(status));
+
+	waitpid(pid_coredump_server, &status, 0);
+	self->pid_coredump_server = -ESRCH;
+	ASSERT_TRUE(WIFEXITED(status));
+	ASSERT_EQ(WEXITSTATUS(status), 0);
+}
+
 TEST_HARNESS_MAIN
diff --git a/tools/testing/selftests/pidfd/pidfd.h b/tools/testing/selftests/pidfd/pidfd.h
index 55bcf81a2b9a..efd74063126e 100644
--- a/tools/testing/selftests/pidfd/pidfd.h
+++ b/tools/testing/selftests/pidfd/pidfd.h
@@ -131,6 +131,26 @@
 #define PIDFD_INFO_EXIT			(1UL << 3) /* Always returned if available, even if not requested */
 #endif
 
+#ifndef PIDFD_INFO_COREDUMP
+#define PIDFD_INFO_COREDUMP	(1UL << 4)
+#endif
+
+#ifndef PIDFD_COREDUMPED
+#define PIDFD_COREDUMPED	(1U << 0) /* Did crash and... */
+#endif
+
+#ifndef PIDFD_COREDUMP_SKIP
+#define PIDFD_COREDUMP_SKIP	(1U << 1) /* coredumping generation was skipped. */
+#endif
+
+#ifndef PIDFD_COREDUMP_USER
+#define PIDFD_COREDUMP_USER	(1U << 2) /* coredump was done as the user. */
+#endif
+
+#ifndef PIDFD_COREDUMP_ROOT
+#define PIDFD_COREDUMP_ROOT	(1U << 3) /* coredump was done as root. */
+#endif
+
 #ifndef PIDFD_THREAD
 #define PIDFD_THREAD O_EXCL
 #endif
@@ -150,6 +170,8 @@ struct pidfd_info {
 	__u32 fsuid;
 	__u32 fsgid;
 	__s32 exit_code;
+	__u32 coredump_mask;
+	__u32 __spare1;
 };
 
 /*