logind: automatically remove SysV + POSIX IPC objects when the users owning them fully log out

1 files changed, 360 insertions, 0 deletions

diff --git a/src/shared/clean-ipc.c b/src/shared/clean-ipc.c
new file mode 100644
index 0000000000..ddd42cc2b2
--- /dev/null
+++ b/src/shared/clean-ipc.c
@@ -0,0 +1,360 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+  This file is part of systemd.
+
+  Copyright 2014 Lennart Poettering
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  systemd is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <sys/ipc.h>
+#include <sys/shm.h>
+#include <sys/sem.h>
+#include <sys/msg.h>
+#include <sys/stat.h>
+#include <sys/mman.h>
+#include <fcntl.h>
+#include <dirent.h>
+#include <mqueue.h>
+
+#include "util.h"
+#include "strv.h"
+#include "clean-ipc.h"
+
+static int clean_sysvipc_shm(uid_t delete_uid) {
+        _cleanup_fclose_ FILE *f = NULL;
+        char line[LINE_MAX];
+        bool first = true;
+        int ret = 0;
+
+        f = fopen("/proc/sysvipc/shm", "re");
+        if (!f) {
+                if (errno == ENOENT)
+                        return 0;
+
+                log_warning("Failed to open /proc/sysvipc/shm: %m");
+                return -errno;
+        }
+
+        FOREACH_LINE(line, f, goto fail) {
+                unsigned n_attached;
+                pid_t cpid, lpid;
+                uid_t uid, cuid;
+                gid_t gid, cgid;
+                int shmid;
+
+                if (first) {
+                        first = false;
+                        continue;
+                }
+
+                truncate_nl(line);
+
+                if (sscanf(line, "%*i %i %*o %*u " PID_FMT " " PID_FMT " %u " UID_FMT " " GID_FMT " " UID_FMT " " GID_FMT,
+                           &shmid, &cpid, &lpid, &n_attached, &uid, &gid, &cuid, &cgid) != 8)
+                        continue;
+
+                if (n_attached > 0)
+                        continue;
+
+                if (uid != delete_uid)
+                        continue;
+
+                if (shmctl(shmid, IPC_RMID, NULL) < 0) {
+
+                        /* Ignore entries that are already deleted */
+                        if (errno == EIDRM || errno == EINVAL)
+                                continue;
+
+                        log_warning("Failed to remove SysV shared memory segment %i: %m", shmid);
+                        ret = -errno;
+                }
+        }
+
+        return ret;
+
+fail:
+        log_warning("Failed to read /proc/sysvipc/shm: %m");
+        return -errno;
+}
+
+static int clean_sysvipc_sem(uid_t delete_uid) {
+        _cleanup_fclose_ FILE *f = NULL;
+        char line[LINE_MAX];
+        bool first = true;
+        int ret = 0;
+
+        f = fopen("/proc/sysvipc/sem", "re");
+        if (!f) {
+                if (errno == ENOENT)
+                        return 0;
+
+                log_warning("Failed to open /proc/sysvipc/sem: %m");
+                return -errno;
+        }
+
+        FOREACH_LINE(line, f, goto fail) {
+                uid_t uid, cuid;
+                gid_t gid, cgid;
+                int semid;
+
+                if (first) {
+                        first = false;
+                        continue;
+                }
+
+                truncate_nl(line);
+
+                if (sscanf(line, "%*i %i %*o %*u " UID_FMT " " GID_FMT " " UID_FMT " " GID_FMT,
+                           &semid, &uid, &gid, &cuid, &cgid) != 5)
+                        continue;
+
+                if (uid != delete_uid)
+                        continue;
+
+                if (semctl(semid, 0, IPC_RMID) < 0) {
+
+                        /* Ignore entries that are already deleted */
+                        if (errno == EIDRM || errno == EINVAL)
+                                continue;
+
+                        log_warning("Failed to remove SysV semaphores object %i: %m", semid);
+                        ret = -errno;
+                }
+        }
+
+        return ret;
+
+fail:
+        log_warning("Failed to read /proc/sysvipc/sem: %m");
+        return -errno;
+}
+
+static int clean_sysvipc_msg(uid_t delete_uid) {
+        _cleanup_fclose_ FILE *f = NULL;
+        char line[LINE_MAX];
+        bool first = true;
+        int ret = 0;
+
+        f = fopen("/proc/sysvipc/msg", "re");
+        if (!f) {
+                if (errno == ENOENT)
+                        return 0;
+
+                log_warning("Failed to open /proc/sysvipc/msg: %m");
+                return -errno;
+        }
+
+        FOREACH_LINE(line, f, goto fail) {
+                uid_t uid, cuid;
+                gid_t gid, cgid;
+                pid_t cpid, lpid;
+                int msgid;
+
+                if (first) {
+                        first = false;
+                        continue;
+                }
+
+                truncate_nl(line);
+
+                if (sscanf(line, "%*i %i %*o %*u %*u " PID_FMT " " PID_FMT " " UID_FMT " " GID_FMT " " UID_FMT " " GID_FMT,
+                           &msgid, &cpid, &lpid, &uid, &gid, &cuid, &cgid) != 7)
+                        continue;
+
+                if (uid != delete_uid)
+                        continue;
+
+                if (msgctl(msgid, IPC_RMID, NULL) < 0) {
+
+                        /* Ignore entries that are already deleted */
+                        if (errno == EIDRM || errno == EINVAL)
+                                continue;
+
+                        log_warning("Failed to remove SysV message queue %i: %m", msgid);
+                        ret = -errno;
+                }
+        }
+
+        return ret;
+
+fail:
+        log_warning("Failed to read /proc/sysvipc/msg: %m");
+        return -errno;
+}
+
+static int clean_posix_shm_internal(DIR *dir, uid_t uid) {
+        struct dirent *de;
+        int ret = 0, r;
+
+        assert(dir);
+
+        FOREACH_DIRENT(de, dir, goto fail) {
+                struct stat st;
+
+                if (STR_IN_SET(de->d_name, "..", "."))
+                        continue;
+
+                if (fstatat(dirfd(dir), de->d_name, &st, AT_SYMLINK_NOFOLLOW) < 0) {
+                        if (errno == ENOENT)
+                                continue;
+
+                        log_warning("Failed to stat() POSIX shared memory segment %s: %m", de->d_name);
+                        ret = -errno;
+                        continue;
+                }
+
+                if (st.st_uid != uid)
+                        continue;
+
+                if (S_ISDIR(st.st_mode)) {
+                        _cleanup_closedir_ DIR *kid;
+
+                        kid = xopendirat(dirfd(dir), de->d_name, O_NOFOLLOW|O_NOATIME);
+                        if (!kid) {
+                                if (errno != ENOENT) {
+                                        log_warning("Failed to enter shared memory directory %s: %m", de->d_name);
+                                        ret = -errno;
+                                }
+                        } else {
+                                r = clean_posix_shm_internal(kid, uid);
+                                if (r < 0)
+                                        ret = r;
+                        }
+
+                        if (unlinkat(dirfd(dir), de->d_name, AT_REMOVEDIR) < 0) {
+
+                                if (errno == ENOENT)
+                                        continue;
+
+                                log_warning("Failed to remove POSIX shared memory directory %s: %m", de->d_name);
+                                ret = -errno;
+                        }
+                } else {
+
+                        if (unlinkat(dirfd(dir), de->d_name, 0) < 0) {
+
+                                if (errno == ENOENT)
+                                        continue;
+
+                                log_warning("Failed to remove POSIX shared memory segment %s: %m", de->d_name);
+                                ret = -errno;
+                        }
+                }
+        }
+
+        return ret;
+
+fail:
+        log_warning("Failed to read /dev/shm: %m");
+        return -errno;
+}
+
+static int clean_posix_shm(uid_t uid) {
+        _cleanup_closedir_ DIR *dir = NULL;
+
+        dir = opendir("/dev/shm");
+        if (!dir) {
+                if (errno == ENOENT)
+                        return 0;
+
+                log_warning("Failed to open /dev/shm: %m");
+                return -errno;
+        }
+
+        return clean_posix_shm_internal(dir, uid);
+}
+
+static int clean_posix_mq(uid_t uid) {
+        _cleanup_closedir_ DIR *dir = NULL;
+        struct dirent *de;
+        int ret = 0;
+
+        dir = opendir("/dev/mqueue");
+        if (!dir) {
+                if (errno == ENOENT)
+                        return 0;
+
+                log_warning("Failed to open /dev/mqueue: %m");
+                return -errno;
+        }
+
+        FOREACH_DIRENT(de, dir, goto fail) {
+                struct stat st;
+                char fn[1+strlen(de->d_name)+1];
+
+                if (STR_IN_SET(de->d_name, "..", "."))
+                        continue;
+
+                if (fstatat(dirfd(dir), de->d_name, &st, AT_SYMLINK_NOFOLLOW) < 0) {
+                        if (errno == ENOENT)
+                                continue;
+
+                        log_warning("Failed to stat() MQ segment %s: %m", de->d_name);
+                        ret = -errno;
+                        continue;
+                }
+
+                if (st.st_uid != uid)
+                        continue;
+
+                fn[0] = '/';
+                strcpy(fn+1, de->d_name);
+
+                if (mq_unlink(fn) < 0) {
+                        if (errno == ENOENT)
+                                continue;
+
+                        log_warning("Failed to unlink POSIX message queue %s: %m", fn);
+                        ret = -errno;
+                }
+        }
+
+        return ret;
+
+fail:
+        log_warning("Failed to read /dev/mqueue: %m");
+        return -errno;
+}
+
+int clean_ipc(uid_t uid) {
+        int ret = 0, r;
+
+        /* Refuse to clean IPC of the root user */
+        if (uid == 0)
+                return 0;
+
+        r = clean_sysvipc_shm(uid);
+        if (r < 0)
+                ret = r;
+
+        r = clean_sysvipc_sem(uid);
+        if (r < 0)
+                ret = r;
+
+        r = clean_sysvipc_msg(uid);
+        if (r < 0)
+                ret = r;
+
+        r = clean_posix_shm(uid);
+        if (r < 0)
+                ret = r;
+
+        r = clean_posix_mq(uid);
+        if (r < 0)
+                ret = r;
+
+        return ret;
+}