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netfilter: nf_reject_ipv4: Fix use-after-free in send_reset

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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 <tejaswit@codeaurora.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Tejaswi Tanikella 2017-10-23 11:46:03 +05:30 committed by Pablo Neira Ayuso
parent 0414c78f14
commit 7400bb4b58
1 changed files with 2 additions and 0 deletions
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2
net/ipv4/netfilter/nf_reject_ipv4.c
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@ -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;