linux-kernel - [03/21] dccp: handle invalid feature options length

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Date:	Thu, 19 May 2011 11:23:33 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Dan Rosenberg <drosenberg@...curity.com>,
	Gerrit Renker <gerrit@....abdn.ac.uk>,
	"David S. Miller" <davem@...emloft.net>
Subject: [03/21] dccp: handle invalid feature options length

2.6.32-longterm review patch.  If anyone has any objections, please let us know.

------------------

From: Dan Rosenberg <drosenberg@...curity.com>

commit a294865978b701e4d0d90135672749531b9a900d upstream.

A length of zero (after subtracting two for the type and len fields) for
the DCCPO_{CHANGE,CONFIRM}_{L,R} options will cause an underflow due to
the subtraction.  The subsequent code may read past the end of the
options value buffer when parsing.  I'm unsure of what the consequences
of this might be, but it's probably not good.

Signed-off-by: Dan Rosenberg <drosenberg@...curity.com>
Acked-by: Gerrit Renker <gerrit@....abdn.ac.uk>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 net/dccp/options.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/net/dccp/options.c
+++ b/net/dccp/options.c
@@ -131,6 +131,8 @@ int dccp_parse_options(struct sock *sk,
 		case DCCPO_CHANGE_L ... DCCPO_CONFIRM_R:
 			if (pkt_type == DCCP_PKT_DATA)      /* RFC 4340, 6 */
 				break;
+			if (len == 0)
+				goto out_invalid_option;
 			rc = dccp_feat_parse_options(sk, dreq, mandatory, opt,
 						    *value, value + 1, len - 1);
 			if (rc)

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