selftests/coredump: add tests for AF_UNIX coredumps
authorChristian Brauner <brauner@kernel.org>
Fri, 16 May 2025 11:25:36 +0000 (13:25 +0200)
committerChristian Brauner <brauner@kernel.org>
Wed, 21 May 2025 11:59:12 +0000 (13:59 +0200)
Add a simple test for generating coredumps via AF_UNIX sockets.

Link: https://lore.kernel.org/20250516-work-coredump-socket-v8-9-664f3caf2516@kernel.org
Acked-by: Luca Boccassi <luca.boccassi@gmail.com>
Reviewed-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
tools/testing/selftests/coredump/stackdump_test.c

index fe3c728..9984413 100644 (file)
@@ -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