linux-kernel - Re: [PATCH 4.4 60/74] ipv6: fix udpv6 sendmsg crash caused by too small MTU

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <1519069573.3422.63.camel@codethink.co.uk>
Date:   Mon, 19 Feb 2018 20:46:13 +0100
From:   Ben Hutchings <ben.hutchings@...ethink.co.uk>
To:     Mike Maloney <maloney@...gle.com>,
        Eric Dumazet <edumazet@...gle.com>
Cc:     stable@...r.kernel.org, syzbot <syzkaller@...glegroups.com>,
        "David S. Miller" <davem@...emloft.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4.4 60/74] ipv6: fix udpv6 sendmsg crash caused by too
 small MTU

On Mon, 2018-01-29 at 13:57 +0100, Greg Kroah-Hartman wrote:
> 4.4-stable review patch.  If anyone has any objections, please let me know.
> 
> ------------------
> 
> From: Mike Maloney <maloney@...gle.com>
> 
> 
> [ Upstream commit 749439bfac6e1a2932c582e2699f91d329658196 ]
[...]
> --- a/net/ipv6/ip6_output.c
> +++ b/net/ipv6/ip6_output.c
> @@ -1246,14 +1246,16 @@ static int ip6_setup_cork(struct sock *s
>  	v6_cork->tclass = tclass;
>  	if (rt->dst.flags & DST_XFRM_TUNNEL)
>  		mtu = np->pmtudisc >= IPV6_PMTUDISC_PROBE ?
> -		      rt->dst.dev->mtu : dst_mtu(&rt->dst);
> +		      READ_ONCE(rt->dst.dev->mtu) : dst_mtu(&rt->dst);
>  	else
>  		mtu = np->pmtudisc >= IPV6_PMTUDISC_PROBE ?
> -		      rt->dst.dev->mtu : dst_mtu(rt->dst.path);
> +		      READ_ONCE(rt->dst.dev->mtu) : dst_mtu(rt->dst.path);
>  	if (np->frag_size < mtu) {
>  		if (np->frag_size)
>  			mtu = np->frag_size;
>  	}
> +	if (mtu < IPV6_MIN_MTU)
> +		return -EINVAL;

This error path appears to leak a reference to rt->dst.

Ben.

>  	cork->base.fragsize = mtu;
>  	if (dst_allfrag(rt->dst.path))
>  		cork->base.flags |= IPCORK_ALLFRAG;
> 
> 
> 
-- 
Ben Hutchings
Software Developer, Codethink Ltd.