From: Neil Horman <nhorman@tuxdriver.com>
To: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Vlad Yasevich <vyasevich@gmail.com>,
"David S. Miller" <davem@davemloft.net>,
linux-sctp@vger.kernel.org, netdev@vger.kernel.org,
kernel-janitors@vger.kernel.org
Subject: Re: [PATCH net] sctp: potential read out of bounds in sctp_ulpevent_type_enabled()
Date: Wed, 13 Sep 2017 10:28:55 -0400 [thread overview]
Message-ID: <20170913142855.GA4320@hmswarspite.think-freely.org> (raw)
In-Reply-To: <20170913092028.idzvduj7ran4li6b@mwanda>
On Wed, Sep 13, 2017 at 12:20:28PM +0300, Dan Carpenter wrote:
> 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@oracle.com>
> ---
> I'm not terribly familiar with sctp and this is a static checker fix.
> Please review it carefully.
>
> diff --git a/include/net/sctp/ulpevent.h b/include/net/sctp/ulpevent.h
> index 1060494ac230..e6873176bea7 100644
> --- a/include/net/sctp/ulpevent.h
> +++ b/include/net/sctp/ulpevent.h
> @@ -154,7 +154,11 @@ static inline int sctp_ulpevent_type_enabled(__u16 sn_type,
> struct sctp_event_subscribe *mask)
> {
> char *amask = (char *) mask;
> - return amask[sn_type - SCTP_SN_TYPE_BASE];
> + int offset = sn_type - SCTP_SN_TYPE_BASE;
> +
> + if (offset >= sizeof(struct sctp_event_subscribe))
> + return 0;
> + return amask[offset];
> }
Acked-by: Neil Horman <nhorman@tuxdriver.com>
>
> /* Given an event subscription, is this event enabled? */
> --
> To unsubscribe from this list: send the line "unsubscribe linux-sctp" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
>
next prev parent reply other threads:[~2017-09-13 14:29 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-13 9:20 [PATCH net] sctp: potential read out of bounds in sctp_ulpevent_type_enabled() Dan Carpenter
2017-09-13 14:28 ` Neil Horman [this message]
2017-09-13 16:25 ` David Miller
2017-09-13 23:00 ` [PATCH v2 " Dan Carpenter
2017-09-14 0:00 ` David Miller
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20170913142855.GA4320@hmswarspite.think-freely.org \
--to=nhorman@tuxdriver.com \
--cc=dan.carpenter@oracle.com \
--cc=davem@davemloft.net \
--cc=kernel-janitors@vger.kernel.org \
--cc=linux-sctp@vger.kernel.org \
--cc=netdev@vger.kernel.org \
--cc=vyasevich@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox