um: adjust size of pid_buf

Linux can have pids up to 4*1024*1024.  To handle such huge numbers
pid_buf needs to be larger.
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/um/drivers/harddog_user.c

@@ -32,7 +32,7 @@ int start_watchdog(int *in_fd_ret, int *out_fd_ret, char *sock)
 {
 	struct dog_data data;
 	int in_fds[2], out_fds[2], pid, n, err;
-	char pid_buf[sizeof("nnnnn\0")], c;
+	char pid_buf[sizeof("nnnnnnn\0")], c;
 	char *pid_args[] = { "/usr/bin/uml_watchdog", "-pid", pid_buf, NULL };
 	char *mconsole_args[] = { "/usr/bin/uml_watchdog", "-mconsole", NULL,
 				  NULL };