tree-wide: use recvmsg_safe() at various places

Let's be extra careful whenever we return from recvmsg() and see
MSG_CTRUNC set. This generally means we ran into a programming error, as
we didn't size the control buffer large enough. It's an error condition
we should at least log about, or propagate up. Hence do that.

This is particularly important when receiving fds, since for those the
control data can be of any size. In particular on stream sockets that's
nasty, because if we miss an fd because of control data truncation we
cannot recover, we might not even realize that we are one off.

(Also, when failing early, if there's any chance the socket might be
AF_UNIX let's close all received fds, all the time. We got this right
most of the time, but there were a few cases missing. God, UNIX is hard
to use)

1 files changed, 4 insertions, 6 deletions

diff --git a/src/udev/udev-ctrl.c b/src/udev/udev-ctrl.c
index b8c0d83a02..d067279f3e 100644
--- a/src/udev/udev-ctrl.c
+++ b/src/udev/udev-ctrl.c
@@ -212,13 +212,11 @@ static int udev_ctrl_connection_event_handler(sd_event_source *s, int fd, uint32
         if (size == 0)
                 return 0; /* Client disconnects? */
 
-        size = recvmsg(fd, &smsg, 0);
-        if (size < 0) {
-                if (errno != EINTR)
-                        return log_error_errno(errno, "Failed to receive ctrl message: %m");
-
+        size = recvmsg_safe(fd, &smsg, 0);
+        if (size == -EINTR)
                 return 0;
-        }
+        if (size < 0)
+                return log_error_errno(size, "Failed to receive ctrl message: %m");
 
         cmsg_close_all(&smsg);