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authorHangbin Liu <liuhangbin@gmail.com>2020-10-27 20:33:13 +0800
committerJakub Kicinski <kuba@kernel.org>2020-10-31 13:16:02 -0700
commit2efdaaaf883a143061296467913c01aa1ff4b3ce (patch)
treece049de5cdd1d34f469b09032eee45a3e762585a /net
parentb59e286be280fa3c2e94a0716ddcee6ba02bc8ba (diff)
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IPv6: reply ICMP error if the first fragment don't include all headers
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>
Diffstat (limited to 'net')
-rw-r--r--net/ipv6/icmp.c8
-rw-r--r--net/ipv6/reassembly.c33
2 files changed, 39 insertions, 2 deletions
diff --git a/net/ipv6/icmp.c b/net/ipv6/icmp.c
index ec448b71bf9a..8956144ea65e 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) {