From: Herbert Xu <herbert@gondor.apana.org.au>
Date: Thu, 20 Dec 2018 21:20:10 +0800
Subject: ipv6: frags: Fix bogus skb->sk in reassembled packets
Patch-mainline: v4.20
Git-commit: d15f5ac8deea936d3adf629421a66a88b42b8a2f
References: CVE-2018-5391 bsc#1103097

It was reported that IPsec would crash when it encounters an IPv6
reassembled packet because skb->sk is non-zero and not a valid
pointer.

This is because skb->sk is now a union with ip_defrag_offset.

This patch fixes this by resetting skb->sk when exiting from
the reassembly code.

Reported-by: Xiumei Mu <xmu@redhat.com>
Fixes: 219badfaade9 ("ipv6: frags: get rid of ip6frag_skb_cb/...")
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Michal Kubecek <mkubecek@suse.cz>

---
 net/ipv6/reassembly.c | 1 +
 1 file changed, 1 insertion(+)

--- a/net/ipv6/reassembly.c
+++ b/net/ipv6/reassembly.c
@@ -383,6 +383,7 @@ static int ip6_frag_reasm(struct frag_queue *fq, struct sk_buff *prev,
 		if (skb_try_coalesce(head, fp, &headstolen, &delta)) {
 			kfree_skb_partial(fp, headstolen);
 		} else {
+			fp->sk = NULL;
 			if (!skb_shinfo(head)->frag_list)
 				skb_shinfo(head)->frag_list = fp;
 			head->data_len += fp->len;