[CVE-2010-4529 Maverick] irda: prevent integer underflow in IRLMP_ENUMDEVICES, CVE-2010-4529

[Leann Ogasawara]

The following changes since commit 98e5bbf03976d01a116c000ec141ec7b5325f759:
  Brad Figg (1):
        UBUNTU: Ubuntu-2.6.35-28.50

are available in the git repository at:

  git://kernel.ubuntu.com/ogasawara/ubuntu-maverick.git CVE-2010-4529

Dan Rosenberg (1):
      irda: prevent integer underflow in IRLMP_ENUMDEVICES, CVE-2010-4529

 net/irda/af_irda.c |   16 +++++++++-------
 1 files changed, 9 insertions(+), 7 deletions(-)

>From c67f25c8d3cca155f07f9969112468cee07cdbf9 Mon Sep 17 00:00:00 2001
From: Dan Rosenberg <drosenberg at vsecurity.com>
Date: Wed, 22 Dec 2010 13:58:27 +0000
Subject: [PATCH] irda: prevent integer underflow in IRLMP_ENUMDEVICES, CVE-2010-4529

CVE-2010-4529

BugLink: http://bugs.launchpad.net/bugs/737823

If the user-provided len is less than the expected offset, the
IRLMP_ENUMDEVICES getsockopt will do a copy_to_user() with a very large
size value.  While this isn't be a security issue on x86 because it will
get caught by the access_ok() check, it may leak large amounts of kernel
heap on other architectures.  In any event, this patch fixes it.

Signed-off-by: Dan Rosenberg <drosenberg at vsecurity.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
(backport of upstream commit fdac1e0697356ac212259f2147aa60c72e334861)

Signed-off-by: Leann Ogasawara <leann.ogasawara at canonical.com>
---
 net/irda/af_irda.c |   16 +++++++++-------
 1 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/net/irda/af_irda.c b/net/irda/af_irda.c
index fd55b51..83ef96e 100644
--- a/net/irda/af_irda.c
+++ b/net/irda/af_irda.c
@@ -2278,6 +2278,14 @@ static int __irda_getsockopt(struct socket *sock, int level, int optname,
 
 	switch (optname) {
 	case IRLMP_ENUMDEVICES:
+
+		/* Offset to first device entry */
+		offset = sizeof(struct irda_device_list) -
+			sizeof(struct irda_device_info);
+
+		if (len < offset)
+			return -EINVAL;
+
 		/* Ask lmp for the current discovery log */
 		discoveries = irlmp_get_discoveries(&list.len, self->mask.word,
 						    self->nslots);
@@ -2287,15 +2295,9 @@ static int __irda_getsockopt(struct socket *sock, int level, int optname,
 		err = 0;
 
 		/* Write total list length back to client */
-		if (copy_to_user(optval, &list,
-				 sizeof(struct irda_device_list) -
-				 sizeof(struct irda_device_info)))
+		if (copy_to_user(optval, &list, offset))
 			err = -EFAULT;
 
-		/* Offset to first device entry */
-		offset = sizeof(struct irda_device_list) -
-			sizeof(struct irda_device_info);
-
 		/* Copy the list itself - watch for overflow */
 		if(list.len > 2048)
 		{
-- 
1.7.0.4