From 7400bb4b5800831581a82f71700af6a5e815c3c8 Mon Sep 17 00:00:00 2001 From: Tejaswi Tanikella Date: Mon, 23 Oct 2017 11:46:03 +0530 Subject: [PATCH] netfilter: nf_reject_ipv4: Fix use-after-free in send_reset niph is not updated after pskb_expand_head changes the skb head. It still points to the freed data, which is then used to update tot_len and checksum. This could cause use-after-free poison crash. Update niph, if ip_route_me_harder does not fail. This only affects the interaction with REJECT targets and br_netfilter. Signed-off-by: Tejaswi Tanikella Signed-off-by: Pablo Neira Ayuso --- net/ipv4/netfilter/nf_reject_ipv4.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/net/ipv4/netfilter/nf_reject_ipv4.c b/net/ipv4/netfilter/nf_reject_ipv4.c index eeacbdaf7cdf..5cd06ba3535d 100644 --- a/net/ipv4/netfilter/nf_reject_ipv4.c +++ b/net/ipv4/netfilter/nf_reject_ipv4.c @@ -132,6 +132,8 @@ void nf_send_reset(struct net *net, struct sk_buff *oldskb, int hook) if (ip_route_me_harder(net, nskb, RTN_UNSPEC)) goto free_nskb; + niph = ip_hdr(nskb); + /* "Never happens" */ if (nskb->len > dst_mtu(skb_dst(nskb))) goto free_nskb; -- 2.20.1