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 <tejaswit@codeaurora.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
diff --git a/net/ipv4/netfilter/nf_reject_ipv4.c b/net/ipv4/netfilter/nf_reject_ipv4.c
index eeacbda..5cd06ba 100644
--- a/net/ipv4/netfilter/nf_reject_ipv4.c
+++ b/net/ipv4/netfilter/nf_reject_ipv4.c
@@ -132,6 +132,8 @@
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;
