udevd: cleanup std{in,our,err} on startup

It occurs, when root-partition has no /dev/console, meaning that kernel
could not open it, and such udevd is started without open filedescriptors
0 1 2. In that case udevd openes its sockets (netlink and control). They
get fds between 0 and 2. Later duping /dev/null to 0 1 2 closes the sockets
and replaces them with /dev/null.

The error condition can also be reproduced by starting udevd with this
command-line:
  udevd --daemon <&- >&- 2>&-

1 files changed, 19 insertions, 11 deletions

diff --git a/udevd.c b/udevd.c
index 23f5fd6980..961ceb587a 100644
--- a/udevd.c
+++ b/udevd.c
@@ -989,6 +989,19 @@ int main(int argc, char *argv[], char *envp[])
 		goto exit;
 	}
 
+	/* make sure std{in,out,err} fd's are in a sane state */
+	fd = open("/dev/null", O_RDWR);
+	if (fd < 0) {
+		fprintf(stderr, "cannot open /dev/null\n");
+		err("cannot open /dev/null");
+	}
+	if (fd > STDIN_FILENO)
+		dup2(fd, STDIN_FILENO);
+	if (write(STDOUT_FILENO, 0, 0) < 0)
+		dup2(fd, STDOUT_FILENO);
+	if (write(STDERR_FILENO, 0, 0) < 0)
+		dup2(fd, STDERR_FILENO);
+
 	/* init sockets to receive events */
 	if (init_udevd_socket() < 0) {
 		if (errno == EADDRINUSE) {
@@ -1064,17 +1077,12 @@ int main(int argc, char *argv[], char *envp[])
 		}
 	}
 
-	/* redirect std fd's */
-	fd = open("/dev/null", O_RDWR);
-	if (fd >= 0) {
-		dup2(fd, STDIN_FILENO);
-		if (!verbose)
-			dup2(fd, STDOUT_FILENO);
-		dup2(fd, STDERR_FILENO);
-		if (fd > STDERR_FILENO)
-			close(fd);
-	} else
-		err("error opening /dev/null: %s", strerror(errno));
+	/* redirect std{out,err} fd's */
+	if (!verbose)
+		dup2(fd, STDOUT_FILENO);
+	dup2(fd, STDERR_FILENO);
+	if (fd > STDERR_FILENO)
+		close(fd);
 
 	/* set scheduling priority for the daemon */
 	setpriority(PRIO_PROCESS, 0, UDEVD_PRIORITY);