From 3ba3458fb9c050718b95275a3310b74415e767e2 Mon Sep 17 00:00:00 2001 From: Jakub Sitnicki Date: Tue, 5 Apr 2016 18:41:08 +0200 Subject: [PATCH] ipv6: Count in extension headers in skb->network_header When sending a UDPv6 message longer than MTU, account for the length of fragmentable IPv6 extension headers in skb->network_header offset. Same as we do in alloc_new_skb path in __ip6_append_data(). This ensures that later on __ip6_make_skb() will make space in headroom for fragmentable extension headers: /* move skb->data to ip header from ext header */ if (skb->data < skb_network_header(skb)) __skb_pull(skb, skb_network_offset(skb)); Prevents a splat due to skb_under_panic: skbuff: skb_under_panic: text:ffffffff8143397b len:2126 put:14 \ head:ffff880005bacf50 data:ffff880005bacf4a tail:0x48 end:0xc0 dev:lo ------------[ cut here ]------------ kernel BUG at net/core/skbuff.c:104! invalid opcode: 0000 [#1] KASAN CPU: 0 PID: 160 Comm: reproducer Not tainted 4.6.0-rc2 #65 [...] Call Trace: [] skb_push+0x79/0x80 [] eth_header+0x2b/0x100 [] neigh_resolve_output+0x210/0x310 [] ip6_finish_output2+0x4a7/0x7c0 [] ip6_output+0x16a/0x280 [] ip6_local_out+0xb1/0xf0 [] ip6_send_skb+0x45/0xd0 [] udp_v6_send_skb+0x246/0x5d0 [] udpv6_sendmsg+0xa6e/0x1090 [...] Reported-by: Ji Jianwen Signed-off-by: Jakub Sitnicki Acked-by: Hannes Frederic Sowa Signed-off-by: David S. Miller --- net/ipv6/ip6_output.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c index 9428345d3a07..bc972e7152c7 100644 --- a/net/ipv6/ip6_output.c +++ b/net/ipv6/ip6_output.c @@ -1090,8 +1090,8 @@ static inline int ip6_ufo_append_data(struct sock *sk, int getfrag(void *from, char *to, int offset, int len, int odd, struct sk_buff *skb), void *from, int length, int hh_len, int fragheaderlen, - int transhdrlen, int mtu, unsigned int flags, - const struct flowi6 *fl6) + int exthdrlen, int transhdrlen, int mtu, + unsigned int flags, const struct flowi6 *fl6) { struct sk_buff *skb; @@ -1116,7 +1116,7 @@ static inline int ip6_ufo_append_data(struct sock *sk, skb_put(skb, fragheaderlen + transhdrlen); /* initialize network header pointer */ - skb_reset_network_header(skb); + skb_set_network_header(skb, exthdrlen); /* initialize protocol header pointer */ skb->transport_header = skb->network_header + fragheaderlen; @@ -1358,7 +1358,7 @@ emsgsize: (rt->dst.dev->features & NETIF_F_UFO) && (sk->sk_type == SOCK_DGRAM) && !udp_get_no_check6_tx(sk)) { err = ip6_ufo_append_data(sk, queue, getfrag, from, length, - hh_len, fragheaderlen, + hh_len, fragheaderlen, exthdrlen, transhdrlen, mtu, flags, fl6); if (err) goto error;