Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Wenwen Wang <wang6495@umn.edu>,
        "David S. Miller" <davem@davemloft.net>
Subject: [PATCH 4.9 141/171] net: socket: fix a missing-check bug
Date:   Thu,  8 Nov 2018 13:51:51 -0800
Message-Id: <20181108215137.187831317@linuxfoundation.org>
In-Reply-To: <20181108215127.257643509@linuxfoundation.org>
References: <20181108215127.257643509@linuxfoundation.org>
User-Agent: quilt/0.65
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

4.9-stable review patch.  If anyone has any objections, please let me know.

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

From: Wenwen Wang <wang6495@umn.edu>

[ Upstream commit b6168562c8ce2bd5a30e213021650422e08764dc ]

In ethtool_ioctl(), the ioctl command 'ethcmd' is checked through a switch
statement to see whether it is necessary to pre-process the ethtool
structure, because, as mentioned in the comment, the structure
ethtool_rxnfc is defined with padding. If yes, a user-space buffer 'rxnfc'
is allocated through compat_alloc_user_space(). One thing to note here is
that, if 'ethcmd' is ETHTOOL_GRXCLSRLALL, the size of the buffer 'rxnfc' is
partially determined by 'rule_cnt', which is actually acquired from the
user-space buffer 'compat_rxnfc', i.e., 'compat_rxnfc->rule_cnt', through
get_user(). After 'rxnfc' is allocated, the data in the original user-space
buffer 'compat_rxnfc' is then copied to 'rxnfc' through copy_in_user(),
including the 'rule_cnt' field. However, after this copy, no check is
re-enforced on 'rxnfc->rule_cnt'. So it is possible that a malicious user
race to change the value in the 'compat_rxnfc->rule_cnt' between these two
copies. Through this way, the attacker can bypass the previous check on
'rule_cnt' and inject malicious data. This can cause undefined behavior of
the kernel and introduce potential security risk.

This patch avoids the above issue via copying the value acquired by
get_user() to 'rxnfc->rule_cn', if 'ethcmd' is ETHTOOL_GRXCLSRLALL.

Signed-off-by: Wenwen Wang <wang6495@umn.edu>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/socket.c |   11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

--- a/net/socket.c
+++ b/net/socket.c
@@ -2774,9 +2774,14 @@ static int ethtool_ioctl(struct net *net
 		    copy_in_user(&rxnfc->fs.ring_cookie,
 				 &compat_rxnfc->fs.ring_cookie,
 				 (void __user *)(&rxnfc->fs.location + 1) -
-				 (void __user *)&rxnfc->fs.ring_cookie) ||
-		    copy_in_user(&rxnfc->rule_cnt, &compat_rxnfc->rule_cnt,
-				 sizeof(rxnfc->rule_cnt)))
+				 (void __user *)&rxnfc->fs.ring_cookie))
+			return -EFAULT;
+		if (ethcmd == ETHTOOL_GRXCLSRLALL) {
+			if (put_user(rule_cnt, &rxnfc->rule_cnt))
+				return -EFAULT;
+		} else if (copy_in_user(&rxnfc->rule_cnt,
+					&compat_rxnfc->rule_cnt,
+					sizeof(rxnfc->rule_cnt)))
 			return -EFAULT;
 	}