early init: fix error handling when opening /dev/console

The comment says "this should never fail", but it definitely can fail
when you have odd initial boot filesystems, or kernel configurations.

So get the error handling right: filp_open() returns an error pointer.
Reported-by: NJesse Barnes <jsbarnes@google.com>
Reported-by: Nyouling 257 <youling257@gmail.com>
Fixes: 8243186f ("fs: remove ksys_dup()")
Cc: Dominik Brodowski <linux@dominikbrodowski.net>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

init/main.c

@@ -1163,7 +1163,7 @@ void console_on_rootfs(void)
 
 	/* Open /dev/console in kernelspace, this should never fail */
 	file = filp_open("/dev/console", O_RDWR, 0);
-	if (!file)
+	if (IS_ERR(file))
 		goto err_out;
 
 	/* create stdin/stdout/stderr, this should never fail */