inet: add RCU protection to inet->opt

We lack proper synchronization to manipulate inet->opt ip_options

Problem is ip_make_skb() calls ip_setup_cork() and
ip_setup_cork() possibly makes a copy of ipc->opt (struct ip_options),
without any protection against another thread manipulating inet->opt.

Another thread can change inet->opt pointer and free old one under us.

Use RCU to protect inet->opt (changed to inet->inet_opt).

Instead of handling atomic refcounts, just copy ip_options when
necessary, to avoid cache line dirtying.

We cant insert an rcu_head in struct ip_options since its included in
skb->cb[], so this patch is large because I had to introduce a new
ip_options_rcu structure.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 11 insertions, 12 deletions

diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
index 74e35e5..cfeca3c 100644
--- a/net/ipv4/icmp.c
+++ b/net/ipv4/icmp.c
@@ -108,8 +108,7 @@ struct icmp_bxm {
 		__be32	       times[3];
 	} data;
 	int head_len;
-	struct ip_options replyopts;
-	unsigned char  optbuf[40];
+	struct ip_options_data replyopts;
 };
 
 /* An array of errno for error messages from dest unreach. */
@@ -333,7 +332,7 @@ static void icmp_reply(struct icmp_bxm *icmp_param, struct sk_buff *skb)
 	struct inet_sock *inet;
 	__be32 daddr;
 
-	if (ip_options_echo(&icmp_param->replyopts, skb))
+	if (ip_options_echo(&icmp_param->replyopts.opt.opt, skb))
 		return;
 
 	sk = icmp_xmit_lock(net);
@@ -347,10 +346,10 @@ static void icmp_reply(struct icmp_bxm *icmp_param, struct sk_buff *skb)
 	daddr = ipc.addr = rt->rt_src;
 	ipc.opt = NULL;
 	ipc.tx_flags = 0;
-	if (icmp_param->replyopts.optlen) {
-		ipc.opt = &icmp_param->replyopts;
-		if (ipc.opt->srr)
-			daddr = icmp_param->replyopts.faddr;
+	if (icmp_param->replyopts.opt.opt.optlen) {
+		ipc.opt = &icmp_param->replyopts.opt;
+		if (ipc.opt->opt.srr)
+			daddr = icmp_param->replyopts.opt.opt.faddr;
 	}
 	{
 		struct flowi4 fl4 = {
@@ -379,8 +378,8 @@ static struct rtable *icmp_route_lookup(struct net *net, struct sk_buff *skb_in,
 					struct icmp_bxm *param)
 {
 	struct flowi4 fl4 = {
-		.daddr = (param->replyopts.srr ?
-			  param->replyopts.faddr : iph->saddr),
+		.daddr = (param->replyopts.opt.opt.srr ?
+			  param->replyopts.opt.opt.faddr : iph->saddr),
 		.saddr = saddr,
 		.flowi4_tos = RT_TOS(tos),
 		.flowi4_proto = IPPROTO_ICMP,
@@ -581,7 +580,7 @@ void icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info)
 					   IPTOS_PREC_INTERNETCONTROL) :
 					  iph->tos;
 
-	if (ip_options_echo(&icmp_param.replyopts, skb_in))
+	if (ip_options_echo(&icmp_param.replyopts.opt.opt, skb_in))
 		goto out_unlock;
 
 
@@ -597,7 +596,7 @@ void icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info)
 	icmp_param.offset = skb_network_offset(skb_in);
 	inet_sk(sk)->tos = tos;
 	ipc.addr = iph->saddr;
-	ipc.opt = &icmp_param.replyopts;
+	ipc.opt = &icmp_param.replyopts.opt;
 	ipc.tx_flags = 0;
 
 	rt = icmp_route_lookup(net, skb_in, iph, saddr, tos,
@@ -613,7 +612,7 @@ void icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info)
 	room = dst_mtu(&rt->dst);
 	if (room > 576)
 		room = 576;
-	room -= sizeof(struct iphdr) + icmp_param.replyopts.optlen;
+	room -= sizeof(struct iphdr) + icmp_param.replyopts.opt.opt.optlen;
 	room -= sizeof(struct icmphdr);
 
 	icmp_param.data_len = skb_in->len - icmp_param.offset;