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/journal/journald-stream.c b/src/journal/journald-stream.c
index 202ac3cda2..4dadbd62be 100644
--- a/src/journal/journald-stream.c
+++ b/src/journal/journald-stream.c
@@ -489,7 +489,7 @@ static int stdout_stream_scan(StdoutStream *s, bool force_flush) {
 }
 
 static int stdout_stream_process(sd_event_source *es, int fd, uint32_t revents, void *userdata) {
-        uint8_t buf[CMSG_SPACE(sizeof(struct ucred))];
+        CMSG_BUFFER_TYPE(CMSG_SPACE(sizeof(struct ucred))) control;
         StdoutStream *s = userdata;
         struct ucred *ucred;
         struct iovec iovec;
@@ -500,8 +500,8 @@ static int stdout_stream_process(sd_event_source *es, int fd, uint32_t revents,
         struct msghdr msghdr = {
                 .msg_iov = &iovec,
                 .msg_iovlen = 1,
-                .msg_control = buf,
-                .msg_controllen = sizeof(buf),
+                .msg_control = &control,
+                .msg_controllen = sizeof(control),
         };
 
         assert(s);