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authorJunwei Hu <hujunwei4@huawei.com>2019-04-02 19:38:04 +0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2019-04-17 08:36:44 +0200
commite33684f9bc4c2bf01c4b6e63048e79b830cacbe1 (patch)
parent9b7984e8ff3b2c9e8685ffee04097ba927347f39 (diff)
ipv6: Fix dangling pointer when ipv6 fragment
[ Upstream commit ef0efcd3bd3fd0589732b67fb586ffd3c8705806 ] At the beginning of ip6_fragment func, the prevhdr pointer is obtained in the ip6_find_1stfragopt func. However, all the pointers pointing into skb header may change when calling skb_checksum_help func with skb->ip_summed = CHECKSUM_PARTIAL condition. The prevhdr pointe will be dangling if it is not reloaded after calling __skb_linearize func in skb_checksum_help func. Here, I add a variable, nexthdr_offset, to evaluate the offset, which does not changes even after calling __skb_linearize func. Fixes: 405c92f7a541 ("ipv6: add defensive check for CHECKSUM_PARTIAL skbs in ip_fragment") Signed-off-by: Junwei Hu <hujunwei4@huawei.com> Reported-by: Wenhao Zhang <zhangwenhao8@huawei.com> Reported-by: syzbot+e8ce541d095e486074fc@syzkaller.appspotmail.com Reviewed-by: Zhiqiang Liu <liuzhiqiang26@huawei.com> Acked-by: Martin KaFai Lau <kafai@fb.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
1 files changed, 3 insertions, 1 deletions
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index b723987761be..11407dd6bc7c 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -592,7 +592,7 @@ int ip6_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
inet6_sk(skb->sk) : NULL;
struct ipv6hdr *tmp_hdr;
struct frag_hdr *fh;
- unsigned int mtu, hlen, left, len;
+ unsigned int mtu, hlen, left, len, nexthdr_offset;
int hroom, troom;
__be32 frag_id;
int ptr, offset = 0, err = 0;
@@ -603,6 +603,7 @@ int ip6_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
goto fail;
hlen = err;
nexthdr = *prevhdr;
+ nexthdr_offset = prevhdr - skb_network_header(skb);
mtu = ip6_skb_dst_mtu(skb);
@@ -637,6 +638,7 @@ int ip6_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
(err = skb_checksum_help(skb)))
goto fail;
+ prevhdr = skb_network_header(skb) + nexthdr_offset;
hroom = LL_RESERVED_SPACE(rt->dst.dev);
if (skb_has_frag_list(skb)) {
int first_len = skb_pagelen(skb);