smackfs: restrict bytes count in smk_set_cipso()

commit 49ec114 upstream.

Oops, I failed to update subject line.

From 07571157c91b98ce1a4aa70967531e64b78e8346 Mon Sep 17 00:00:00 2001
From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Date: Mon, 12 Apr 2021 22:25:06 +0900
Subject: smackfs: restrict bytes count in smk_set_cipso()

Commit 7ef4c19 ("smackfs: restrict bytes count in smackfs write
functions") missed that count > SMK_CIPSOMAX check applies to only
format == SMK_FIXED24_FMT case.

Reported-by: syzbot <syzbot+77c53db50c9fff774e8e@syzkaller.appspotmail.com>
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

security/smack/smackfs.c

@@ -855,6 +855,8 @@ static ssize_t smk_set_cipso(struct file *file, const char __user *buf,
 	if (format == SMK_FIXED24_FMT &&
 	    (count < SMK_CIPSOMIN || count > SMK_CIPSOMAX))
 		return -EINVAL;
+	if (count > PAGE_SIZE)
+		return -EINVAL;
 
 	data = memdup_user_nul(buf, count);
 	if (IS_ERR(data))