[PATCH stable v5.4 1/2] ICMPv6: Add ICMPv6 Parameter Problem, code 3 definition

[PATCH stable v5.4 1/2] ICMPv6: Add ICMPv6 Parameter Problem, code 3 definition

[Aviraj CJ]

From: Hangbin Liu <liuhangbin@gmail.com>

commit b59e286be280fa3c2e94a0716ddcee6ba02bc8ba upstream.

Based on RFC7112, Section 6:

   IANA has added the following "Type 4 - Parameter Problem" message to
   the "Internet Control Message Protocol version 6 (ICMPv6) Parameters"
   registry:

      CODE     NAME/DESCRIPTION
       3       IPv6 First Fragment has incomplete IPv6 Header Chain

Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Aviraj CJ <acj@cisco.com>
---
 include/uapi/linux/icmpv6.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/include/uapi/linux/icmpv6.h b/include/uapi/linux/icmpv6.h
index 2622b5a3e616..9a31ea2ad1cf 100644
--- a/include/uapi/linux/icmpv6.h
+++ b/include/uapi/linux/icmpv6.h
@@ -137,6 +137,7 @@ struct icmp6hdr {
 #define ICMPV6_HDR_FIELD		0
 #define ICMPV6_UNK_NEXTHDR		1
 #define ICMPV6_UNK_OPTION		2
+#define ICMPV6_HDR_INCOMP		3
 
 /*
  *	constants for (set|get)sockopt
-- 
2.26.2.Cisco

[PATCH stable v5.4 2/2] IPv6: reply ICMP error if the first fragment don't include all headers

[Aviraj CJ]

From: Hangbin Liu <liuhangbin@gmail.com>

commit 2efdaaaf883a143061296467913c01aa1ff4b3ce upstream.

Based on RFC 8200, Section 4.5 Fragment Header:

  -  If the first fragment does not include all headers through an
     Upper-Layer header, then that fragment should be discarded and
     an ICMP Parameter Problem, Code 3, message should be sent to
     the source of the fragment, with the Pointer field set to zero.

Checking each packet header in IPv6 fast path will have performance impact,
so I put the checking in ipv6_frag_rcv().

As the packet may be any kind of L4 protocol, I only checked some common
protocols' header length and handle others by (offset + 1) > skb->len.
Also use !(frag_off & htons(IP6_OFFSET)) to catch atomic fragments
(fragmented packet with only one fragment).

When send ICMP error message, if the 1st truncated fragment is ICMP message,
icmp6_send() will break as is_ineligible() return true. So I added a check
in is_ineligible() to let fragment packet with nexthdr ICMP but no ICMP header
return false.

Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Aviraj CJ <acj@cisco.com>
---
 net/ipv6/icmp.c       |  8 +++++++-
 net/ipv6/reassembly.c | 33 ++++++++++++++++++++++++++++++++-
 2 files changed, 39 insertions(+), 2 deletions(-)

diff --git a/net/ipv6/icmp.c b/net/ipv6/icmp.c
index 7d3a3894f785..e9bb89131e02 100644
--- a/net/ipv6/icmp.c
+++ b/net/ipv6/icmp.c
@@ -158,7 +158,13 @@ static bool is_ineligible(const struct sk_buff *skb)
 		tp = skb_header_pointer(skb,
 			ptr+offsetof(struct icmp6hdr, icmp6_type),
 			sizeof(_type), &_type);
-		if (!tp || !(*tp & ICMPV6_INFOMSG_MASK))
+
+		/* Based on RFC 8200, Section 4.5 Fragment Header, return
+		 * false if this is a fragment packet with no icmp header info.
+		 */
+		if (!tp && frag_off != 0)
+			return false;
+		else if (!tp || !(*tp & ICMPV6_INFOMSG_MASK))
 			return true;
 	}
 	return false;
diff --git a/net/ipv6/reassembly.c b/net/ipv6/reassembly.c
index 1f5d4d196dcc..c8cf1bbad74a 100644
--- a/net/ipv6/reassembly.c
+++ b/net/ipv6/reassembly.c
@@ -42,6 +42,8 @@
 #include <linux/skbuff.h>
 #include <linux/slab.h>
 #include <linux/export.h>
+#include <linux/tcp.h>
+#include <linux/udp.h>
 
 #include <net/sock.h>
 #include <net/snmp.h>
@@ -322,7 +324,9 @@ static int ipv6_frag_rcv(struct sk_buff *skb)
 	struct frag_queue *fq;
 	const struct ipv6hdr *hdr = ipv6_hdr(skb);
 	struct net *net = dev_net(skb_dst(skb)->dev);
-	int iif;
+	__be16 frag_off;
+	int iif, offset;
+	u8 nexthdr;
 
 	if (IP6CB(skb)->flags & IP6SKB_FRAGMENTED)
 		goto fail_hdr;
@@ -351,6 +355,33 @@ static int ipv6_frag_rcv(struct sk_buff *skb)
 		return 1;
 	}
 
+	/* RFC 8200, Section 4.5 Fragment Header:
+	 * If the first fragment does not include all headers through an
+	 * Upper-Layer header, then that fragment should be discarded and
+	 * an ICMP Parameter Problem, Code 3, message should be sent to
+	 * the source of the fragment, with the Pointer field set to zero.
+	 */
+	nexthdr = hdr->nexthdr;
+	offset = ipv6_skip_exthdr(skb, skb_transport_offset(skb), &nexthdr, &frag_off);
+	if (offset >= 0) {
+		/* Check some common protocols' header */
+		if (nexthdr == IPPROTO_TCP)
+			offset += sizeof(struct tcphdr);
+		else if (nexthdr == IPPROTO_UDP)
+			offset += sizeof(struct udphdr);
+		else if (nexthdr == IPPROTO_ICMPV6)
+			offset += sizeof(struct icmp6hdr);
+		else
+			offset += 1;
+
+		if (!(frag_off & htons(IP6_OFFSET)) && offset > skb->len) {
+			__IP6_INC_STATS(net, __in6_dev_get_safely(skb->dev),
+					IPSTATS_MIB_INHDRERRORS);
+			icmpv6_param_prob(skb, ICMPV6_HDR_INCOMP, 0);
+			return -1;
+		}
+	}
+
 	iif = skb->dev ? skb->dev->ifindex : 0;
 	fq = fq_find(net, fhdr->identification, hdr, iif);
 	if (fq) {
-- 
2.26.2.Cisco

Re: [PATCH stable v5.4 2/2] IPv6: reply ICMP error if the first fragment don't include all headers

[Greg KH]

On Sat, Jan 30, 2021 at 05:24:52PM +0530, Aviraj CJ wrote:
> From: Hangbin Liu <liuhangbin@gmail.com>
> 
> commit 2efdaaaf883a143061296467913c01aa1ff4b3ce upstream.
> 
> Based on RFC 8200, Section 4.5 Fragment Header:
> 
>   -  If the first fragment does not include all headers through an
>      Upper-Layer header, then that fragment should be discarded and
>      an ICMP Parameter Problem, Code 3, message should be sent to
>      the source of the fragment, with the Pointer field set to zero.
> 
> Checking each packet header in IPv6 fast path will have performance impact,
> so I put the checking in ipv6_frag_rcv().
> 
> As the packet may be any kind of L4 protocol, I only checked some common
> protocols' header length and handle others by (offset + 1) > skb->len.
> Also use !(frag_off & htons(IP6_OFFSET)) to catch atomic fragments
> (fragmented packet with only one fragment).
> 
> When send ICMP error message, if the 1st truncated fragment is ICMP message,
> icmp6_send() will break as is_ineligible() return true. So I added a check
> in is_ineligible() to let fragment packet with nexthdr ICMP but no ICMP header
> return false.
> 
> Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
> Signed-off-by: Jakub Kicinski <kuba@kernel.org>
> Signed-off-by: Aviraj CJ <acj@cisco.com>
> ---
>  net/ipv6/icmp.c       |  8 +++++++-
>  net/ipv6/reassembly.c | 33 ++++++++++++++++++++++++++++++++-
>  2 files changed, 39 insertions(+), 2 deletions(-)

Both now queued up, thanks.

greg k-h