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

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Date:   Tue, 11 May 2021 09:07:01 -0700
From:   Casey Schaufler <casey@...aufler-ca.com>
To:     Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
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,
        Casey Schaufler <casey@...aufler-ca.com>
Subject: Re: [syzbot] WARNING in smk_set_cipso (2)

On 4/12/2021 6:28 AM, Tetsuo Handa wrote:
> 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>

Added to smack-next. Thank you.

> ---
>  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))