Re: Kernel memory corruption in CIPSO labeled TCP packets processing.

[Nazarov Sergey <s-nazarov@yandex.ru>]

18.01.2019, 20:17, "Paul Moore" <paul@paul-moore.com>:
> Yes, this is extra overhead, but it is in an error path so I'm not
> overly concerned about the performance impact on the given connection.
>
> I will admit that it isn't an ideal solution from a LSM/NetLabel
> perspective, but historically the netdev folks have not been overly
> receptive to changes which negatively impact the core network stack
> regardless of how important it may be for the LSMs. If we could
> modify icmp_send() so that it works regardless of the caller's
> location in the stack, that would be great, I'm just not sure it would
> be deemed acceptable. I suggested the approach I did because I think
> that has the best chance of getting merged.
>
> Regardless, I would encourage you to put together a patch and post it
> for review, I think that's the best way to get a response. If you
> aren't able, or aren't comfortable, submitting a patch please let me
> know.
> --
> paul moore
> www.paul-moore.com

May be something like that?

[PATCH 1/2] Add IP options parameter to icmp_send
---
 include/net/icmp.h    |    9 ++++++++-
 net/ipv4/icmp.c       |    7 ++++---
 2 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/include/net/icmp.h b/include/net/icmp.h
index 6ac3a5b..e0f709d 100644
--- a/include/net/icmp.h
+++ b/include/net/icmp.h
@@ -22,6 +22,7 @@
 
 #include <net/inet_sock.h>
 #include <net/snmp.h>
+#include <net/ip.h>
 
 struct icmp_err {
   int		errno;
@@ -39,7 +40,13 @@ struct icmp_err {
 struct sk_buff;
 struct net;
 
-void icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info);
+void __icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info,
+		 const struct ip_options *opt);
+static inline void icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info)
+{
+	__icmp_send(skb_in, type, code, info, &IPCB(skb_in)->opt);
+}
+
 int icmp_rcv(struct sk_buff *skb);
 int icmp_err(struct sk_buff *skb, u32 info);
 int icmp_init(void);
diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
index 065997f..3f24414 100644
--- a/net/ipv4/icmp.c
+++ b/net/ipv4/icmp.c
@@ -570,7 +570,8 @@ static void icmp_reply(struct icmp_bxm *icmp_param, struct sk_buff *skb)
  *			MUST reply to only the first fragment.
  */
 
-void icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info)
+void __icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info,
+		 const struct ip_options *opt)
 {
 	struct iphdr *iph;
 	int room;
@@ -691,7 +692,7 @@ void icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info)
 					  iph->tos;
 	mark = IP4_REPLY_MARK(net, skb_in->mark);
 
-	if (ip_options_echo(net, &icmp_param.replyopts.opt.opt, skb_in))
+	if (__ip_options_echo(net, &icmp_param.replyopts.opt.opt, skb_in, opt))
 		goto out_unlock;
 
 
@@ -742,7 +743,7 @@ void icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info)
 	local_bh_enable();
 out:;
 }
-EXPORT_SYMBOL(icmp_send);
+EXPORT_SYMBOL(__icmp_send);
 
 
 static void icmp_socket_deliver(struct sk_buff *skb, u32 info)

---
[PATCH 2/2] Extract IP options in cipso_v4_error
---
 include/net/ip.h      |    2 ++
 net/ipv4/cipso_ipv4.c |   11 +++++++++--
 net/ipv4/ip_options.c |   22 +++++++++++++++++-----
 3 files changed, 28 insertions(+), 7 deletions(-)

diff --git a/include/net/ip.h b/include/net/ip.h
index 8866bfc..f0e8d06 100644
--- a/include/net/ip.h
+++ b/include/net/ip.h
@@ -667,6 +667,8 @@ static inline int ip_options_echo(struct net *net, struct ip_options *dopt,
 }
 
 void ip_options_fragment(struct sk_buff *skb);
+int __ip_options_compile(struct net *net, struct ip_options *opt,
+			 struct sk_buff *skb, __be32 *info);
 int ip_options_compile(struct net *net, struct ip_options *opt,
 		       struct sk_buff *skb);
 int ip_options_get(struct net *net, struct ip_options_rcu **optp,
diff --git a/net/ipv4/cipso_ipv4.c b/net/ipv4/cipso_ipv4.c
index 777fa3b..86599e9 100644
--- a/net/ipv4/cipso_ipv4.c
+++ b/net/ipv4/cipso_ipv4.c
@@ -1735,13 +1735,20 @@ int cipso_v4_validate(const struct sk_buff *skb, unsigned char **option)
  */
 void cipso_v4_error(struct sk_buff *skb, int error, u32 gateway)
 {
+	unsigned char optbuf[sizeof(struct ip_options) + 40];
+	struct ip_options *opt = (struct ip_options *)optbuf;
+
 	if (ip_hdr(skb)->protocol == IPPROTO_ICMP || error != -EACCES)
 		return;
 
+	opt->optlen = ip_hdr(skb)->ihl*4 - sizeof(struct iphdr);
+	if (__ip_options_compile(dev_net(skb->dev), opt, skb, NULL))
+		return;
+
 	if (gateway)
-		icmp_send(skb, ICMP_DEST_UNREACH, ICMP_NET_ANO, 0);
+		__icmp_send(skb, ICMP_DEST_UNREACH, ICMP_NET_ANO, 0, opt);
 	else
-		icmp_send(skb, ICMP_DEST_UNREACH, ICMP_HOST_ANO, 0);
+		__icmp_send(skb, ICMP_DEST_UNREACH, ICMP_HOST_ANO, 0, opt);
 }
 
 /**
diff --git a/net/ipv4/ip_options.c b/net/ipv4/ip_options.c
index ed194d4..32a3504 100644
--- a/net/ipv4/ip_options.c
+++ b/net/ipv4/ip_options.c
@@ -251,8 +251,9 @@ static void spec_dst_fill(__be32 *spec_dst, struct sk_buff *skb)
  * If opt == NULL, then skb->data should point to IP header.
  */
 
-int ip_options_compile(struct net *net,
-		       struct ip_options *opt, struct sk_buff *skb)
+int __ip_options_compile(struct net *net,
+			 struct ip_options *opt, struct sk_buff *skb,
+			 __be32 *info)
 {
 	__be32 spec_dst = htonl(INADDR_ANY);
 	unsigned char *pp_ptr = NULL;
@@ -468,11 +469,22 @@ int ip_options_compile(struct net *net,
 		return 0;
 
 error:
-	if (skb) {
-		icmp_send(skb, ICMP_PARAMETERPROB, 0, htonl((pp_ptr-iph)<<24));
-	}
+	if (info)
+		*info = htonl((pp_ptr-iph)<<24);
 	return -EINVAL;
 }
+
+int ip_options_compile(struct net *net,
+		       struct ip_options *opt, struct sk_buff *skb)
+{
+	int ret;
+	__be32 info;
+
+	ret = __ip_options_compile(net, opt, skb, &info);
+	if (ret != 0 && skb)
+		icmp_send(skb, ICMP_PARAMETERPROB, 0, info);
+	return ret;
+}
 EXPORT_SYMBOL(ip_options_compile);
 
 /*

---