netdev - Re: [4.9.10] ip_route_me_harder() reading off-slab

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: <20170217073928.GA25854@breakpoint.cc>
Date:   Fri, 17 Feb 2017 08:39:28 +0100
From:   Florian Westphal <fw@...len.de>
To:     Daniel J Blueman <daniel@...ra.org>
Cc:     Netdev <netdev@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        David Ahern <dsa@...ulusnetworks.com>,
        Jan Beulich <JBeulich@...e.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        netfilter-devel@...r.kernel.org, pablo@...filter.org
Subject: Re: [4.9.10] ip_route_me_harder() reading off-slab

Daniel J Blueman <daniel@...ra.org> wrote:

[ CC nf-devel, pablo ]

> When booting a VM in libvirt/KVM attached to a local bridge and KASAN
> enabled on 4.9.10, we see a stream of KASAN warnings about off-slab
> access [1].
> 
> Let me know if you'd like more debug.

Does this patch help?

Subject: [PATCH nf] netfilter: use skb_to_full_sk in ip_route_me_harder

inet_sk(skb->sk) is illegal in case skb is attached to request socket.

Fixes: ca6fb0651883 ("tcp: attach SYNACK messages to request sockets instead of listener")
Reported by: Daniel J Blueman <daniel@...ra.org>
Signed-off-by: Florian Westphal <fw@...len.de>
---
 net/ipv4/netfilter.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/net/ipv4/netfilter.c b/net/ipv4/netfilter.c
index b3cc1335adbc..c0cc6aa8cfaa 100644
--- a/net/ipv4/netfilter.c
+++ b/net/ipv4/netfilter.c
@@ -23,7 +23,8 @@ int ip_route_me_harder(struct net *net, struct sk_buff *skb, unsigned int addr_t
 	struct rtable *rt;
 	struct flowi4 fl4 = {};
 	__be32 saddr = iph->saddr;
-	__u8 flags = skb->sk ? inet_sk_flowi_flags(skb->sk) : 0;
+	const struct sock *sk = skb_to_full_sk(skb);
+	__u8 flags = sk ? inet_sk_flowi_flags(sk) : 0;
 	struct net_device *dev = skb_dst(skb)->dev;
 	unsigned int hh_len;
 
@@ -40,7 +41,7 @@ int ip_route_me_harder(struct net *net, struct sk_buff *skb, unsigned int addr_t
 	fl4.daddr = iph->daddr;
 	fl4.saddr = saddr;
 	fl4.flowi4_tos = RT_TOS(iph->tos);
-	fl4.flowi4_oif = skb->sk ? skb->sk->sk_bound_dev_if : 0;
+	fl4.flowi4_oif = sk ? sk->sk_bound_dev_if : 0;
 	if (!fl4.flowi4_oif)
 		fl4.flowi4_oif = l3mdev_master_ifindex(dev);
 	fl4.flowi4_mark = skb->mark;
@@ -61,7 +62,7 @@ int ip_route_me_harder(struct net *net, struct sk_buff *skb, unsigned int addr_t
 	    xfrm_decode_session(skb, flowi4_to_flowi(&fl4), AF_INET) == 0) {
 		struct dst_entry *dst = skb_dst(skb);
 		skb_dst_set(skb, NULL);
-		dst = xfrm_lookup(net, dst, flowi4_to_flowi(&fl4), skb->sk, 0);
+		dst = xfrm_lookup(net, dst, flowi4_to_flowi(&fl4), sk, 0);
 		if (IS_ERR(dst))
 			return PTR_ERR(dst);
 		skb_dst_set(skb, dst);
-- 
2.10.2