[hardy, lucid, lucid/fsl-imx51, maverick, maverick/ti-omap4, natty, natty/ti-omap4 CVE 1/1] Bluetooth: Prevent buffer overflow in l2cap config request

[Andy Whitcroft]

From: Dan Rosenberg <drosenberg at vsecurity.com>

A remote user can provide a small value for the command size field in
the command header of an l2cap configuration request, resulting in an
integer underflow when subtracting the size of the configuration request
header.  This results in copying a very large amount of data via
memcpy() and destroying the kernel heap.  Check for underflow.

Signed-off-by: Dan Rosenberg <drosenberg at vsecurity.com>
Cc: stable <stable at kernel.org>
Signed-off-by: Gustavo F. Padovan <padovan at profusion.mobi>

(backported from commit 7ac28817536797fd40e9646452183606f9e17f71)
CVE-2011-2497
BugLink: http://bugs.launchpad.net/bugs/838423
Signed-off-by: Andy Whitcroft <apw at canonical.com>
---
 net/bluetooth/l2cap.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/net/bluetooth/l2cap.c b/net/bluetooth/l2cap.c
index 0676111..f59b7d5 100644
--- a/net/bluetooth/l2cap.c
+++ b/net/bluetooth/l2cap.c
@@ -1632,7 +1632,7 @@ static inline int l2cap_config_req(struct l2cap_conn *conn, struct l2cap_cmd_hdr
 
 	/* Reject if config buffer is too small. */
 	len = cmd_len - sizeof(*req);
-	if (l2cap_pi(sk)->conf_len + len > sizeof(l2cap_pi(sk)->conf_req)) {
+	if (len < 0 || l2cap_pi(sk)->conf_len + len > sizeof(l2cap_pi(sk)->conf_req)) {
 		l2cap_send_cmd(conn, cmd->ident, L2CAP_CONF_RSP,
 				l2cap_build_conf_rsp(sk, rsp,
 					L2CAP_CONF_REJECT, flags), rsp);
-- 
1.7.4.1