bus: add minimal locking around the memfd cache

[elogind.git] / src / libsystemd-bus / sd-bus.c

diff --git a/src/libsystemd-bus/sd-bus.c b/src/libsystemd-bus/sd-bus.c
index 7b937d999973a74d7c673e8f4abe77295d7e9b8e..5e66a31162611ac2d7ae988840aa55950a458320 100644 (file)
--- a/src/libsystemd-bus/sd-bus.c
+++ b/src/libsystemd-bus/sd-bus.c
@@ -26,6 +26,8 @@
 #include <netdb.h>
 #include <sys/poll.h>
 #include <byteswap.h>
+#include <sys/mman.h>
+#include <pthread.h>
 
 #include "util.h"
 #include "macro.h"
@@ -43,6 +45,18 @@
 
 static int bus_poll(sd_bus *bus, bool need_more, uint64_t timeout_usec);
 
+static void bus_close_fds(sd_bus *b) {
+        assert(b);
+
+        if (b->input_fd >= 0)
+                close_nointr_nofail(b->input_fd);
+
+        if (b->output_fd >= 0 && b->output_fd != b->input_fd)
+                close_nointr_nofail(b->output_fd);
+
+        b->input_fd = b->output_fd = -1;
+}
+
 static void bus_free(sd_bus *b) {
         struct filter_callback *f;
         struct object_callback *c;
@@ -50,7 +64,10 @@ static void bus_free(sd_bus *b) {
 
         assert(b);
 
-        sd_bus_close(b);
+        bus_close_fds(b);
+
+        if (b->kdbus_buffer)
+                munmap(b->kdbus_buffer, KDBUS_POOL_SIZE);
 
         free(b->rbuffer);
         free(b->unique_name);
@@ -90,6 +107,8 @@ static void bus_free(sd_bus *b) {
 
         bus_kernel_flush_memfd(b);
 
+        assert_se(pthread_mutex_destroy(&b->memfd_cache_mutex) == 0);
+
         free(b);
 }
 
@@ -103,10 +122,13 @@ int sd_bus_new(sd_bus **ret) {
         if (!r)
                 return -ENOMEM;
 
-        r->n_ref = 1;
+        r->n_ref = REFCNT_INIT;
         r->input_fd = r->output_fd = -1;
         r->message_version = 1;
         r->negotiate_fds = true;
+        r->original_pid = getpid();
+
+        assert_se(pthread_mutex_init(&r->memfd_cache_mutex, NULL) == 0);
 
         /* We guarantee that wqueue always has space for at least one
          * entry */
@@ -129,6 +151,8 @@ int sd_bus_set_address(sd_bus *bus, const char *address) {
                 return -EPERM;
         if (!address)
                 return -EINVAL;
+        if (bus_pid_changed(bus))
+                return -ECHILD;
 
         a = strdup(address);
         if (!a)
@@ -149,6 +173,8 @@ int sd_bus_set_fd(sd_bus *bus, int input_fd, int output_fd) {
                 return -EINVAL;
         if (output_fd < 0)
                 return -EINVAL;
+        if (bus_pid_changed(bus))
+                return -ECHILD;
 
         bus->input_fd = input_fd;
         bus->output_fd = output_fd;
@@ -166,6 +192,8 @@ int sd_bus_set_exec(sd_bus *bus, const char *path, char *const argv[]) {
                 return -EINVAL;
         if (strv_isempty(argv))
                 return -EINVAL;
+        if (bus_pid_changed(bus))
+                return -ECHILD;
 
         p = strdup(path);
         if (!p)
@@ -191,6 +219,8 @@ int sd_bus_set_bus_client(sd_bus *bus, int b) {
                 return -EINVAL;
         if (bus->state != BUS_UNSET)
                 return -EPERM;
+        if (bus_pid_changed(bus))
+                return -ECHILD;
 
         bus->bus_client = !!b;
         return 0;
@@ -201,6 +231,8 @@ int sd_bus_set_negotiate_fds(sd_bus *bus, int b) {
                 return -EINVAL;
         if (bus->state != BUS_UNSET)
                 return -EPERM;
+        if (bus_pid_changed(bus))
+                return -ECHILD;
 
         bus->negotiate_fds = !!b;
         return 0;
@@ -213,6 +245,8 @@ int sd_bus_set_server(sd_bus *bus, int b, sd_id128_t server_id) {
                 return -EINVAL;
         if (bus->state != BUS_UNSET)
                 return -EPERM;
+        if (bus_pid_changed(bus))
+                return -ECHILD;
 
         bus->is_server = !!b;
         bus->server_id = server_id;
@@ -224,6 +258,8 @@ int sd_bus_set_anonymous(sd_bus *bus, int b) {
                 return -EINVAL;
         if (bus->state != BUS_UNSET)
                 return -EPERM;
+        if (bus_pid_changed(bus))
+                return -ECHILD;
 
         bus->anonymous_auth = !!b;
         return 0;
@@ -812,6 +848,8 @@ int sd_bus_start(sd_bus *bus) {
                 return -EINVAL;
         if (bus->state != BUS_UNSET)
                 return -EPERM;
+        if (bus_pid_changed(bus))
+                return -ECHILD;
 
         bus->state = BUS_OPENING;
 
@@ -921,22 +959,29 @@ fail:
 void sd_bus_close(sd_bus *bus) {
         if (!bus)
                 return;
+        if (bus->state == BUS_CLOSED)
+                return;
+        if (bus_pid_changed(bus))
+                return;
 
-        if (bus->input_fd >= 0)
-                close_nointr_nofail(bus->input_fd);
-        if (bus->output_fd >= 0 && bus->output_fd != bus->input_fd)
-                close_nointr_nofail(bus->output_fd);
+        bus->state = BUS_CLOSED;
 
-        bus->input_fd = bus->output_fd = -1;
+        if (!bus->is_kernel)
+                bus_close_fds(bus);
+
+        /* We'll leave the fd open in case this is a kernel bus, since
+         * there might still be memblocks around that reference this
+         * bus, and they might need to invoke the
+         * KDBUS_CMD_MSG_RELEASE ioctl on the fd when they are
+         * freed. */
 }
 
 sd_bus *sd_bus_ref(sd_bus *bus) {
         if (!bus)
                 return NULL;
 
-        assert(bus->n_ref > 0);
+        assert_se(REFCNT_INC(bus->n_ref) >= 2);
 
-        bus->n_ref++;
         return bus;
 }
 
@@ -944,10 +989,7 @@ sd_bus *sd_bus_unref(sd_bus *bus) {
         if (!bus)
                 return NULL;
 
-        assert(bus->n_ref > 0);
-        bus->n_ref--;
-
-        if (bus->n_ref <= 0)
+        if (REFCNT_DEC(bus->n_ref) <= 0)
                 bus_free(bus);
 
         return NULL;
@@ -956,8 +998,10 @@ sd_bus *sd_bus_unref(sd_bus *bus) {
 int sd_bus_is_open(sd_bus *bus) {
         if (!bus)
                 return -EINVAL;
+        if (bus_pid_changed(bus))
+                return -ECHILD;
 
-        return bus->state != BUS_UNSET && bus->input_fd >= 0;
+        return BUS_IS_OPEN(bus->state);
 }
 
 int sd_bus_can_send(sd_bus *bus, char type) {
@@ -965,8 +1009,10 @@ int sd_bus_can_send(sd_bus *bus, char type) {
 
         if (!bus)
                 return -EINVAL;
-        if (bus->output_fd < 0)
+        if (bus->state == BUS_UNSET)
                 return -ENOTCONN;
+        if (bus_pid_changed(bus))
+                return -ECHILD;
 
         if (type == SD_BUS_TYPE_UNIX_FD) {
                 if (!bus->negotiate_fds)
@@ -989,6 +1035,8 @@ int sd_bus_get_server_id(sd_bus *bus, sd_id128_t *server_id) {
                 return -EINVAL;
         if (!server_id)
                 return -EINVAL;
+        if (bus_pid_changed(bus))
+                return -ECHILD;
 
         r = bus_ensure_running(bus);
         if (r < 0)
@@ -1016,9 +1064,6 @@ static int dispatch_wqueue(sd_bus *bus) {
         assert(bus);
         assert(bus->state == BUS_RUNNING || bus->state == BUS_HELLO);
 
-        if (bus->output_fd < 0)
-                return -ENOTCONN;
-
         while (bus->wqueue_size > 0) {
 
                 if (bus->is_kernel)
@@ -1063,9 +1108,6 @@ static int dispatch_rqueue(sd_bus *bus, sd_bus_message **m) {
         assert(m);
         assert(bus->state == BUS_RUNNING || bus->state == BUS_HELLO);
 
-        if (bus->input_fd < 0)
-                return -ENOTCONN;
-
         if (bus->rqueue_size > 0) {
                 /* Dispatch a queued message */
 
@@ -1101,12 +1143,12 @@ int sd_bus_send(sd_bus *bus, sd_bus_message *m, uint64_t *serial) {
 
         if (!bus)
                 return -EINVAL;
-        if (bus->state == BUS_UNSET)
-                return -ENOTCONN;
-        if (bus->output_fd < 0)
+        if (!BUS_IS_OPEN(bus->state))
                 return -ENOTCONN;
         if (!m)
                 return -EINVAL;
+        if (bus_pid_changed(bus))
+                return -ECHILD;
 
         if (m->n_fds > 0) {
                 r = sd_bus_can_send(bus, SD_BUS_TYPE_UNIX_FD);
@@ -1214,9 +1256,7 @@ int sd_bus_send_with_reply(
 
         if (!bus)
                 return -EINVAL;
-        if (bus->state == BUS_UNSET)
-                return -ENOTCONN;
-        if (bus->output_fd < 0)
+        if (!BUS_IS_OPEN(bus->state))
                 return -ENOTCONN;
         if (!m)
                 return -EINVAL;
@@ -1226,6 +1266,8 @@ int sd_bus_send_with_reply(
                 return -EINVAL;
         if (m->header->flags & SD_BUS_MESSAGE_NO_REPLY_EXPECTED)
                 return -EINVAL;
+        if (bus_pid_changed(bus))
+                return -ECHILD;
 
         r = hashmap_ensure_allocated(&bus->reply_callbacks, uint64_hash_func, uint64_compare_func);
         if (r < 0)
@@ -1281,6 +1323,8 @@ int sd_bus_send_with_reply_cancel(sd_bus *bus, uint64_t serial) {
                 return -EINVAL;
         if (serial == 0)
                 return -EINVAL;
+        if (bus_pid_changed(bus))
+                return -ECHILD;
 
         c = hashmap_remove(bus->reply_callbacks, &serial);
         if (!c)
@@ -1298,11 +1342,8 @@ int bus_ensure_running(sd_bus *bus) {
 
         assert(bus);
 
-        if (bus->input_fd < 0)
+        if (bus->state == BUS_UNSET || bus->state == BUS_CLOSED)
                 return -ENOTCONN;
-        if (bus->state == BUS_UNSET)
-                return -ENOTCONN;
-
         if (bus->state == BUS_RUNNING)
                 return 1;
 
@@ -1335,9 +1376,7 @@ int sd_bus_send_with_reply_and_block(
 
         if (!bus)
                 return -EINVAL;
-        if (bus->output_fd < 0)
-                return -ENOTCONN;
-        if (bus->state == BUS_UNSET)
+        if (!BUS_IS_OPEN(bus->state))
                 return -ENOTCONN;
         if (!m)
                 return -EINVAL;
@@ -1347,6 +1386,8 @@ int sd_bus_send_with_reply_and_block(
                 return -EINVAL;
         if (bus_error_is_dirty(error))
                 return -EINVAL;
+        if (bus_pid_changed(bus))
+                return -ECHILD;
 
         r = bus_ensure_running(bus);
         if (r < 0)
@@ -1453,10 +1494,12 @@ int sd_bus_send_with_reply_and_block(
 int sd_bus_get_fd(sd_bus *bus) {
         if (!bus)
                 return -EINVAL;
-        if (bus->input_fd < 0)
+        if (!BUS_IS_OPEN(bus->state))
                 return -ENOTCONN;
         if (bus->input_fd != bus->output_fd)
                 return -EPERM;
+        if (bus_pid_changed(bus))
+                return -ECHILD;
 
         return bus->input_fd;
 }
@@ -1466,10 +1509,10 @@ int sd_bus_get_events(sd_bus *bus) {
 
         if (!bus)
                 return -EINVAL;
-        if (bus->state == BUS_UNSET)
-                return -ENOTCONN;
-        if (bus->input_fd < 0)
+        if (!BUS_IS_OPEN(bus->state))
                 return -ENOTCONN;
+        if (bus_pid_changed(bus))
+                return -ECHILD;
 
         if (bus->state == BUS_OPENING)
                 flags |= POLLOUT;
@@ -1497,10 +1540,10 @@ int sd_bus_get_timeout(sd_bus *bus, uint64_t *timeout_usec) {
                 return -EINVAL;
         if (!timeout_usec)
                 return -EINVAL;
-        if (bus->state == BUS_UNSET)
-                return -ENOTCONN;
-        if (bus->input_fd < 0)
+        if (!BUS_IS_OPEN(bus->state))
                 return -ENOTCONN;
+        if (bus_pid_changed(bus))
+                return -ECHILD;
 
         if (bus->state == BUS_AUTHENTICATING) {
                 *timeout_usec = bus->auth_timeout;
@@ -1996,8 +2039,8 @@ int sd_bus_process(sd_bus *bus, sd_bus_message **ret) {
 
         if (!bus)
                 return -EINVAL;
-        if (bus->input_fd < 0)
-                return -ENOTCONN;
+        if (bus_pid_changed(bus))
+                return -ECHILD;
 
         /* We don't allow recursively invoking sd_bus_process(). */
         if (bus->processing)
@@ -2006,6 +2049,7 @@ int sd_bus_process(sd_bus *bus, sd_bus_message **ret) {
         switch (bus->state) {
 
         case BUS_UNSET:
+        case BUS_CLOSED:
                 return -ENOTCONN;
 
         case BUS_OPENING:
@@ -2046,7 +2090,7 @@ static int bus_poll(sd_bus *bus, bool need_more, uint64_t timeout_usec) {
 
         assert(bus);
 
-        if (bus->input_fd < 0)
+        if (!BUS_IS_OPEN(bus->state))
                 return -ENOTCONN;
 
         e = sd_bus_get_events(bus);
@@ -2092,10 +2136,11 @@ int sd_bus_wait(sd_bus *bus, uint64_t timeout_usec) {
 
         if (!bus)
                 return -EINVAL;
-        if (bus->state == BUS_UNSET)
-                return -ENOTCONN;
-        if (bus->input_fd < 0)
+        if (!BUS_IS_OPEN(bus->state))
                 return -ENOTCONN;
+        if (bus_pid_changed(bus))
+                return -ECHILD;
+
         if (bus->rqueue_size > 0)
                 return 0;
 
@@ -2107,10 +2152,10 @@ int sd_bus_flush(sd_bus *bus) {
 
         if (!bus)
                 return -EINVAL;
-        if (bus->state == BUS_UNSET)
-                return -ENOTCONN;
-        if (bus->output_fd < 0)
+        if (!BUS_IS_OPEN(bus->state))
                 return -ENOTCONN;
+        if (bus_pid_changed(bus))
+                return -ECHILD;
 
         r = bus_ensure_running(bus);
         if (r < 0)
@@ -2140,6 +2185,8 @@ int sd_bus_add_filter(sd_bus *bus, sd_bus_message_handler_t callback, void *user
                 return -EINVAL;
         if (!callback)
                 return -EINVAL;
+        if (bus_pid_changed(bus))
+                return -ECHILD;
 
         f = new0(struct filter_callback, 1);
         if (!f)
@@ -2159,6 +2206,8 @@ int sd_bus_remove_filter(sd_bus *bus, sd_bus_message_handler_t callback, void *u
                 return -EINVAL;
         if (!callback)
                 return -EINVAL;
+        if (bus_pid_changed(bus))
+                return -ECHILD;
 
         LIST_FOREACH(callbacks, f, bus->filter_callbacks) {
                 if (f->callback == callback && f->userdata == userdata) {
@@ -2188,6 +2237,8 @@ static int bus_add_object(
                 return -EINVAL;
         if (!callback)
                 return -EINVAL;
+        if (bus_pid_changed(bus))
+                return -ECHILD;
 
         r = hashmap_ensure_allocated(&bus->object_callbacks, string_hash_func, string_compare_func);
         if (r < 0)
@@ -2233,6 +2284,8 @@ static int bus_remove_object(
                 return -EINVAL;
         if (!callback)
                 return -EINVAL;
+        if (bus_pid_changed(bus))
+                return -ECHILD;
 
         c = hashmap_get(bus->object_callbacks, path);
         if (!c)
@@ -2273,6 +2326,8 @@ int sd_bus_add_match(sd_bus *bus, const char *match, sd_bus_message_handler_t ca
                 return -EINVAL;
         if (!match)
                 return -EINVAL;
+        if (bus_pid_changed(bus))
+                return -ECHILD;
 
         if (bus->bus_client) {
                 r = bus_add_match_internal(bus, match);
@@ -2300,6 +2355,8 @@ int sd_bus_remove_match(sd_bus *bus, const char *match, sd_bus_message_handler_t
                 return -EINVAL;
         if (!match)
                 return -EINVAL;
+        if (bus_pid_changed(bus))
+                return -ECHILD;
 
         if (bus->bus_client)
                 r = bus_remove_match_internal(bus, match);
@@ -2327,6 +2384,10 @@ int sd_bus_emit_signal(
 
         if (!bus)
                 return -EINVAL;
+        if (!BUS_IS_OPEN(bus->state))
+                return -ENOTCONN;
+        if (bus_pid_changed(bus))
+                return -ECHILD;
 
         r = sd_bus_message_new_signal(bus, path, interface, member, &m);
         if (r < 0)
@@ -2357,6 +2418,10 @@ int sd_bus_call_method(
 
         if (!bus)
                 return -EINVAL;
+        if (!BUS_IS_OPEN(bus->state))
+                return -ENOTCONN;
+        if (bus_pid_changed(bus))
+                return -ECHILD;
 
         r = sd_bus_message_new_method_call(bus, destination, path, interface, member, &m);
         if (r < 0)
@@ -2388,6 +2453,10 @@ int sd_bus_reply_method_return(
                 return -EPERM;
         if (call->header->type != SD_BUS_MESSAGE_TYPE_METHOD_CALL)
                 return -EINVAL;
+        if (!BUS_IS_OPEN(bus->state))
+                return -ENOTCONN;
+        if (bus_pid_changed(bus))
+                return -ECHILD;
 
         if (call->header->flags & SD_BUS_MESSAGE_NO_REPLY_EXPECTED)
                 return 0;
@@ -2423,6 +2492,10 @@ int sd_bus_reply_method_error(
                 return -EINVAL;
         if (!sd_bus_error_is_set(e))
                 return -EINVAL;
+        if (!BUS_IS_OPEN(bus->state))
+                return -ENOTCONN;
+        if (bus_pid_changed(bus))
+                return -ECHILD;
 
         if (call->header->flags & SD_BUS_MESSAGE_NO_REPLY_EXPECTED)
                 return 0;
@@ -2433,3 +2506,12 @@ int sd_bus_reply_method_error(
 
         return sd_bus_send(bus, m, NULL);
 }
+
+bool bus_pid_changed(sd_bus *bus) {
+        assert(bus);
+
+        /* We don't support people creating a bus connection and
+         * keeping it around over a fork(). Let's complain. */
+
+        return bus->original_pid != getpid();
+}