bus: add minimal locking around the memfd cache

We want to allow clients to process an sd_bus_message on a different
thread than it was received on. Since unreffing a bus message might
readd some of its memfds to the memfd cache add some minimal locking
around the cache.

1 files changed, 5 insertions, 0 deletions

diff --git a/src/libsystemd-bus/sd-bus.c b/src/libsystemd-bus/sd-bus.c
index fd19ff32b0..5e66a31162 100644
--- a/src/libsystemd-bus/sd-bus.c
+++ b/src/libsystemd-bus/sd-bus.c
@@ -27,6 +27,7 @@
 #include <sys/poll.h>
 #include <byteswap.h>
 #include <sys/mman.h>
+#include <pthread.h>
 
 #include "util.h"
 #include "macro.h"
@@ -106,6 +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);
 }
 
@@ -125,6 +128,8 @@ int sd_bus_new(sd_bus **ret) {
         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 */
         r->wqueue = new(sd_bus_message*, 1);