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

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Message-Id: <11471341548341163@sas2-7b909973f402.qloud-c.yandex.net>
Date:   Thu, 24 Jan 2019 17:46:03 +0300
From:   Nazarov Sergey <s-nazarov@...dex.ru>
To:     Paul Moore <paul@...l-moore.com>
Cc:     "linux-security-module@...r.kernel.org" 
        <linux-security-module@...r.kernel.org>,
        "selinux@...r.kernel.org" <selinux@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Casey Schaufler <casey@...aufler-ca.com>
Subject: Re: Kernel memory corruption in CIPSO labeled TCP packets processing.

22.01.2019, 20:48, "Paul Moore" <paul@...l-moore.com>:
>
> Yes, exactly. If you don't pass the skb it shouldn't attempt to call
> icmp_send() in case of error.
>
> --
> paul moore
> www.paul-moore.com

You are right, sorry. We can do that without ip_options_compile modification.
Simplified patch 2:
---
 net/ipv4/cipso_ipv4.c |   18 ++++++++++++++++--
 1 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/cipso_ipv4.c b/net/ipv4/cipso_ipv4.c
index 777fa3b..a4ed0a4 100644
--- a/net/ipv4/cipso_ipv4.c
+++ b/net/ipv4/cipso_ipv4.c
@@ -1735,13 +1735,27 @@ 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;
 
+       /* 
+        * We might be called above the IP layer,
+        * so we can not use icmp_send and IPCB here.
+        */
+
+       memset(opt, 0, sizeof(struct ip_options));
+       opt->optlen = ip_hdr(skb)->ihl*4 - sizeof(struct iphdr);
+       memcpy(opt->__data, (unsigned char *)&(ip_hdr(skb)[1]), opt->optlen);
+       if (ip_options_compile(dev_net(skb->dev), opt, 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);
 }
 
 /**