Dapper CVE: bio: take care not overflow page count when mapping/copying user data

[Tim Gardner]

The following changes since commit 352701fdc50086ac0db65862e16dc8b20918d174:
  Steve Conklin (1):
        UBUNTU: Ubuntu-2.6.15-55.93

are available in the git repository at:

  git://kernel.ubuntu.com/rtg/ubuntu-dapper.git CVE-2010-4162

Tim Gardner (1):
      bio: take care not overflow page count when mapping/copying user data, CVE-2010-4162

 fs/bio.c |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)

>From e6326904fee89c475f6875f3787931601ac14a33 Mon Sep 17 00:00:00 2001
From: Tim Gardner <tim.gardner at canonical.com>
Date: Fri, 18 Feb 2011 12:57:38 -0700
Subject: [PATCH] bio: take care not overflow page count when mapping/copying user data, CVE-2010-4162

BugLink: http://bugs.launchpad.net/bugs/721441

CVE-2010-4162

backport of commit cb4644cac4a2797afc847e6c92736664d4b0ea34 upstream.

If the iovec is being set up in a way that causes uaddr + PAGE_SIZE
to overflow, we could end up attempting to map a huge number of
pages. Check for this invalid input type.

Reported-by: Dan Rosenberg <drosenberg at vsecurity.com>
Signed-off-by: Jens Axboe <jaxboe at fusionio.com>
Signed-off-by: Greg Kroah-Hartman <gregkh at suse.de>
Signed-off-by: Tim Gardner <tim.gardner at canonical.com>
---
 fs/bio.c |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)

diff --git a/fs/bio.c b/fs/bio.c
index 460554b..f776d0a 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -574,6 +574,12 @@ static struct bio *__bio_map_user_iov(request_queue_t *q,
 		unsigned long end = (uaddr + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
 		unsigned long start = uaddr >> PAGE_SHIFT;
 
+		/*
+		 * Overflow, abort
+		 */
+		if (end < start)
+			return ERR_PTR(-EINVAL);
+
 		nr_pages += end - start;
 		/*
 		 * transfer and buffer must be aligned to at least hardsector
-- 
1.7.0.4