netdev - Re: [PATCH v2 net] sctp: potential read out of bounds in sctp_ulpevent_type

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Message-Id: <20170913.170019.543516362575770735.davem@davemloft.net>
Date:   Wed, 13 Sep 2017 17:00:19 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     dan.carpenter@...cle.com
Cc:     vyasevich@...il.com, nhorman@...driver.com,
        linux-sctp@...r.kernel.org, netdev@...r.kernel.org,
        kernel-janitors@...r.kernel.org
Subject: Re: [PATCH v2 net] sctp: potential read out of bounds in
 sctp_ulpevent_type_enabled()

From: Dan Carpenter <dan.carpenter@...cle.com>
Date: Thu, 14 Sep 2017 02:00:54 +0300

> This code causes a static checker warning because Smatch doesn't trust
> anything that comes from skb->data.  I've reviewed this code and I do
> think skb->data can be controlled by the user here.
> 
> The sctp_event_subscribe struct has 13 __u8 fields and we want to see
> if ours is non-zero.  sn_type can be any value in the 0-USHRT_MAX range.
> We're subtracting SCTP_SN_TYPE_BASE which is 1 << 15 so we could read
> either before the start of the struct or after the end.
> 
> This is a very old bug and it's surprising that it would go undetected
> for so long but my theory is that it just doesn't have a big impact so
> it would be hard to notice.
> 
> Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
> ---
> v2:  Use reverse-christmas-tree local variable ordering.

Applied and queued up for -stable, thanks.