linux-kernel - Re: [syzbot] WARNING in smk_set

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Date:   Mon, 12 Apr 2021 22:28:15 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
To:     casey@...aufler-ca.com
Cc:     jmorris@...ei.org, linux-kernel@...r.kernel.org, serge@...lyn.com,
        linux-security-module@...r.kernel.org,
        syzbot <syzbot+77c53db50c9fff774e8e@...kaller.appspotmail.com>,
        syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] WARNING in smk_set_cipso (2)

Commit 7ef4c19d245f3dc2 ("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@...kaller.appspotmail.com>
Signed-off-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
---
 security/smack/smackfs.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/security/smack/smackfs.c b/security/smack/smackfs.c
index 22ded2c26089..1ad7d0d1ea62 100644
--- a/security/smack/smackfs.c
+++ b/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))
-- 
2.18.4