sd-bus: rework how we initialize struct sockaddr_un

Let's use structured initialization, but more importantly, let's
increase salen by 1, if we reference AF_UNIX sockets in the file system,
so that they also contain the trailing NUL byte. This is what unix(7)
suggests to do, hence follow it.

1 files changed, 15 insertions, 7 deletions

diff --git a/src/libsystemd/sd-bus/sd-bus.c b/src/libsystemd/sd-bus/sd-bus.c
index d6c0095161..85558d9c05 100644
--- a/src/libsystemd/sd-bus/sd-bus.c
+++ b/src/libsystemd/sd-bus/sd-bus.c
@@ -733,17 +733,25 @@ static int parse_unix_address(sd_bus *b, const char **p, char **guid) {
                 if (l >= sizeof(b->sockaddr.un.sun_path)) /* We insist on NUL termination */
                         return -E2BIG;
 
-                b->sockaddr.un.sun_family = AF_UNIX;
-                strncpy(b->sockaddr.un.sun_path, path, sizeof(b->sockaddr.un.sun_path));
-                b->sockaddr_size = offsetof(struct sockaddr_un, sun_path) + l;
-        } else if (abstract) {
+                b->sockaddr.un = (struct sockaddr_un) {
+                        .sun_family = AF_UNIX,
+                };
+
+                memcpy(b->sockaddr.un.sun_path, path, l);
+                b->sockaddr_size = offsetof(struct sockaddr_un, sun_path) + l + 1;
+
+        } else {
+                assert(abstract);
+
                 l = strlen(abstract);
                 if (l >= sizeof(b->sockaddr.un.sun_path) - 1) /* We insist on NUL termination */
                         return -E2BIG;
 
-                b->sockaddr.un.sun_family = AF_UNIX;
-                b->sockaddr.un.sun_path[0] = 0;
-                strncpy(b->sockaddr.un.sun_path+1, abstract, sizeof(b->sockaddr.un.sun_path)-1);
+                b->sockaddr.un = (struct sockaddr_un) {
+                        .sun_family = AF_UNIX,
+                };
+
+                memcpy(b->sockaddr.un.sun_path+1, abstract, l);
                 b->sockaddr_size = offsetof(struct sockaddr_un, sun_path) + 1 + l;
         }