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Date: Mon, 27 Feb 2017 22:41:48 +0800 From: Daniel J Blueman <daniel@...ra.org> To: Florian Westphal <fw@...len.de> 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 On 17 February 2017 at 15:39, Florian Westphal <fw@...len.de> wrote: > 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); Apologies for the delays; this also addresses the issue just fine. Tested-by: Daniel J Blueman <daniel@...ra.org> Dan -- Daniel J Blueman
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