From: Pablo Neira Ayuso <pablo@netfilter.org>
To: phil.turnbull@oracle.com
Cc: netfilter-devel@vger.kernel.org,
Patrick McHardy <kaber@trash.net>,
Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>,
"David S. Miller" <davem@davemloft.net>,
"open list:NETFILTER ({IP,IP6,ARP,EB,NF}TABLES)"
<coreteam@netfilter.org>,
"open list:NETWORKING [GENERAL]" <netdev@vger.kernel.org>,
open list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH nf] netfilter: nfnetlink: correctly validate length of batch messages
Date: Mon, 15 Feb 2016 20:27:12 +0100 [thread overview]
Message-ID: <20160215192712.GA4116@salvia> (raw)
In-Reply-To: <1454438205-13147-1-git-send-email-phil.turnbull@oracle.com>
On Tue, Feb 02, 2016 at 01:36:45PM -0500, phil.turnbull@oracle.com wrote:
> From: Phil Turnbull <phil.turnbull@oracle.com>
>
> If nlh->nlmsg_len is zero then an infinite loop is triggered because
> 'skb_pull(skb, msglen);' pulls zero bytes.
>
> The calculation in nlmsg_len() underflows if 'nlh->nlmsg_len <
> NLMSG_HDRLEN' which bypasses the length validation and will later
> trigger an out-of-bound read.
>
> If the length validation does fail then the malformed batch message is
> copied back to userspace. However, we cannot do this because the
> nlh->nlmsg_len can be invalid. This leads to an out-of-bounds read in
> netlink_ack:
>
> [ 41.455421] ==================================================================
> [ 41.456431] BUG: KASAN: slab-out-of-bounds in memcpy+0x1d/0x40 at addr ffff880119e79340
> [ 41.456431] Read of size 4294967280 by task a.out/987
> [ 41.456431] =============================================================================
> [ 41.456431] BUG kmalloc-512 (Not tainted): kasan: bad access detected
> [ 41.456431] -----------------------------------------------------------------------------
> ...
> [ 41.456431] Bytes b4 ffff880119e79310: 00 00 00 00 d5 03 00 00 b0 fb fe ff 00 00 00 00 ................
> [ 41.456431] Object ffff880119e79320: 20 00 00 00 10 00 05 00 00 00 00 00 00 00 00 00 ...............
> [ 41.456431] Object ffff880119e79330: 14 00 0a 00 01 03 fc 40 45 56 11 22 33 10 00 05 .......@EV."3...
> [ 41.456431] Object ffff880119e79340: f0 ff ff ff 88 99 aa bb 00 14 00 0a 00 06 fe fb ................
> ^^ start of batch nlmsg with
> nlmsg_len=4294967280
> ...
> [ 41.456431] Memory state around the buggy address:
> [ 41.456431] ffff880119e79400: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> [ 41.456431] ffff880119e79480: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> [ 41.456431] >ffff880119e79500: 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc fc
> [ 41.456431] ^
> [ 41.456431] ffff880119e79580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> [ 41.456431] ffff880119e79600: fc fc fc fc fc fc fc fc fc fc fb fb fb fb fb fb
> [ 41.456431] ==================================================================
>
> Fix this with better validation of nlh->nlmsg_len and by setting
> NFNL_BATCH_FAILURE if any batch message fails length validation.
>
> CAP_NET_ADMIN is required to trigger the bugs.
Applied, thanks.
prev parent reply other threads:[~2016-02-15 19:27 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-02 18:36 [PATCH nf] netfilter: nfnetlink: correctly validate length of batch messages phil.turnbull
2016-02-15 19:27 ` Pablo Neira Ayuso [this message]
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