tree-wide: make sure our control buffers are properly aligned

We always need to make them unions with a "struct cmsghdr" in them, so
that things properly aligned. Otherwise we might end up at an unaligned
address and the counting goes all wrong, possibly making the kernel
refuse our buffers.

Also, let's make sure we initialize the control buffers to zero when
sending, but leave them uninitialized when reading.

Both the alignment and the initialization thing is mentioned in the
cmsg(3) man page.

1 files changed, 3 insertions, 3 deletions

diff --git a/src/udev/udev-ctrl.c b/src/udev/udev-ctrl.c
index d067279f3e..1e51f22e26 100644
--- a/src/udev/udev-ctrl.c
+++ b/src/udev/udev-ctrl.c
@@ -189,12 +189,12 @@ static int udev_ctrl_connection_event_handler(sd_event_source *s, int fd, uint32
         _cleanup_(udev_ctrl_disconnect_and_listen_againp) struct udev_ctrl *uctrl = NULL;
         struct udev_ctrl_msg_wire msg_wire;
         struct iovec iov = IOVEC_MAKE(&msg_wire, sizeof(struct udev_ctrl_msg_wire));
-        char cred_msg[CMSG_SPACE(sizeof(struct ucred))];
+        CMSG_BUFFER_TYPE(CMSG_SPACE(sizeof(struct ucred))) control;
         struct msghdr smsg = {
                 .msg_iov = &iov,
                 .msg_iovlen = 1,
-                .msg_control = cred_msg,
-                .msg_controllen = sizeof(cred_msg),
+                .msg_control = &control,
+                .msg_controllen = sizeof(control),
         };
         struct cmsghdr *cmsg;
         struct ucred *cred;