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

11 files changed, 464 insertions, 2 deletions

diff --git a/.gitignore b/.gitignore
index 2e17c72aba..74792b3a15 100644
--- a/.gitignore
+++ b/.gitignore
@@ -148,6 +148,7 @@
 /test-id128
 /test-inhibit
 /test-install
+/test-ipcrm
 /test-job-type
 /test-journal
 /test-journal-enum
diff --git a/Makefile.am b/Makefile.am
index 8dcbaca3d6..311ff09d4e 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -795,7 +795,9 @@ libsystemd_shared_la_SOURCES = \
 	src/shared/bus-label.h \
 	src/shared/gpt.h \
 	src/shared/generator.h \
-	src/shared/generator.c
+	src/shared/generator.c \
+	src/shared/clean-ipc.h \
+	src/shared/clean-ipc.c
 
 nodist_libsystemd_shared_la_SOURCES = \
 	src/shared/errno-from-name.h \
@@ -1176,7 +1178,8 @@ manual_tests += \
 	test-cgroup \
 	test-install \
 	test-watchdog \
-	test-log
+	test-log \
+	test-ipcrm
 
 tests += \
 	test-job-type \
@@ -1392,6 +1395,13 @@ test_log_SOURCES = \
 test_log_LDADD = \
 	libsystemd-core.la
 
+test_ipcrm_SOURCES = \
+	src/test/test-ipcrm.c
+
+test_ipcrm_LDADD = \
+	libsystemd-shared.la \
+	-lrt
+
 test_ellipsize_SOURCES = \
 	src/test/test-ellipsize.c
 
diff --git a/man/logind.conf.xml b/man/logind.conf.xml
index ce8f5097cc..99140917ac 100644
--- a/man/logind.conf.xml
+++ b/man/logind.conf.xml
@@ -317,6 +317,26 @@
                                 to.</para></listitem>
                         </varlistentry>
 
+                        <varlistentry>
+                                <term><varname>RemoveIPC=</varname></term>
+
+                                <listitem><para>Controls whether
+                                System V and POSIX IPC objects
+                                belonging to the user shall be removed
+                                when she or he fully logs out. Takes a
+                                boolean argument. If enabled the user
+                                may not consume IPC resources after
+                                the last of his sessions
+                                terminated. This covers System V
+                                semaphores, shared memory and message
+                                queues, as well as POSIX shared memory
+                                and message queues. Note that IPC
+                                objects of the root user are excluded
+                                from the effect of this
+                                setting. Defaults to
+                                on.</para></listitem>
+                        </varlistentry>
+
                 </variablelist>
         </refsect1>
 
diff --git a/src/login/logind-gperf.gperf b/src/login/logind-gperf.gperf
index d870f88cd8..006f7286c5 100644
--- a/src/login/logind-gperf.gperf
+++ b/src/login/logind-gperf.gperf
@@ -31,3 +31,4 @@ Login.LidSwitchIgnoreInhibited,    config_parse_bool,          0, offsetof(Manag
 Login.IdleAction,                  config_parse_handle_action, 0, offsetof(Manager, idle_action)
 Login.IdleActionSec,               config_parse_sec,           0, offsetof(Manager, idle_action_usec)
 Login.RuntimeDirectorySize,        config_parse_tmpfs_size,    0, offsetof(Manager, runtime_dir_size)
+Login.RemoveIPC,                   config_parse_bool,          0, offsetof(Manager, remove_ipc)
diff --git a/src/login/logind-user.c b/src/login/logind-user.c
index 9bbe879571..961cbcb27b 100644
--- a/src/login/logind-user.c
+++ b/src/login/logind-user.c
@@ -35,6 +35,7 @@
 #include "bus-util.h"
 #include "bus-error.h"
 #include "conf-parser.h"
+#include "clean-ipc.h"
 #include "logind-user.h"
 
 User* user_new(Manager *m, uid_t uid, gid_t gid, const char *name) {
@@ -572,6 +573,13 @@ int user_finalize(User *u) {
         if (k < 0)
                 r = k;
 
+        /* Clean SysV + POSIX IPC objects */
+        if (u->manager->remove_ipc) {
+                k = clean_ipc(u->uid);
+                if (k < 0)
+                        r = k;
+        }
+
         unlink(u->state_file);
         user_add_to_gc_queue(u);
 
diff --git a/src/login/logind.c b/src/login/logind.c
index 2d734ff26f..8ba8a9155b 100644
--- a/src/login/logind.c
+++ b/src/login/logind.c
@@ -49,6 +49,7 @@ Manager *manager_new(void) {
 
         m->n_autovts = 6;
         m->reserve_vt = 6;
+        m->remove_ipc = true;
         m->inhibit_delay_max = 5 * USEC_PER_SEC;
         m->handle_power_key = HANDLE_POWEROFF;
         m->handle_suspend_key = HANDLE_SUSPEND;
diff --git a/src/login/logind.conf b/src/login/logind.conf
index ddc23b8aca..79f96ec05b 100644
--- a/src/login/logind.conf
+++ b/src/login/logind.conf
@@ -25,3 +25,4 @@
 #IdleAction=ignore
 #IdleActionSec=30min
 #RuntimeDirectorySize=10%
+#RemoveIPC=yes
diff --git a/src/login/logind.h b/src/login/logind.h
index 533554d4bb..31353eff02 100644
--- a/src/login/logind.h
+++ b/src/login/logind.h
@@ -120,6 +120,8 @@ struct Manager {
         bool hibernate_key_ignore_inhibited;
         bool lid_switch_ignore_inhibited;
 
+        bool remove_ipc;
+
         Hashmap *polkit_registry;
 
         sd_event_source *lid_switch_ignore_event_source;
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;
+}
diff --git a/src/shared/clean-ipc.h b/src/shared/clean-ipc.h
new file mode 100644
index 0000000000..2de57fad26
--- /dev/null
+++ b/src/shared/clean-ipc.h
@@ -0,0 +1,26 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+#pragma once
+
+/***
+  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/types.h>
+
+int clean_ipc(uid_t uid);
diff --git a/src/test/test-ipcrm.c b/src/test/test-ipcrm.c
new file mode 100644
index 0000000000..4944bf6ad9
--- /dev/null
+++ b/src/test/test-ipcrm.c
@@ -0,0 +1,32 @@
+/*-*- 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 "util.h"
+#include "clean-ipc.h"
+
+int main(int argc, char *argv[]) {
+        uid_t uid;
+
+        assert_se(argc == 2);
+        assert_se(parse_uid(argv[1], &uid) >= 0);
+
+        return clean_ipc(uid) < 0 ? EXIT_FAILURE : EXIT_SUCCESS;
+}