[ovs-dev] [PATCH branch-2.9] conntrack: Fix ICMPv4 error data L4 length check.

Vishal Deep Ajmera vishal.deep.ajmera at ericsson.com
Mon Sep 23 06:44:40 UTC 2019


From: Darrell Ball <dlu998 at gmail.com>

The ICMPv4 error data L4 length check was found to be too strict for TCP,
expecting a minimum of 20 rather than 8 bytes.  This worked by
hapenstance for other inner protocols.  The approach is to explicitly
handle the ICMPv4 error data L4 length check and to do this for all
supported inner protocols in the same way.  Making the code common
between protocols also allows the existing ICMPv4 related UDP tests to
cover TCP and ICMP inner protocol cases.
Note that ICMPv6 does not have an 8 byte limit for error L4 data.

Fixes: a489b16854b5 ("conntrack: New userspace connection tracker.")
CC: Daniele Di Proietto <diproiettod at ovn.org>
Reported-at: https://mail.openvswitch.org/pipermail/ovs-dev/2019-August/361949.html
Reported-by: Vishal Deep Ajmera <vishal.deep.ajmera at ericsson.com>
Signed-off-by: Vishal Deep Ajmera <vishal.deep.ajmera at ericsson.com>
Co-authored-by: Vishal Deep Ajmera <vishal.deep.ajmera at ericsson.com>
Signed-off-by: Darrell Ball <dlu998 at gmail.com>
Signed-off-by: Ben Pfaff <blp at ovn.org>
(cherry picked from commit 6c2a93064afe8d812e4506880d1fd8f96108f92a)
---
 lib/conntrack.c | 41 ++++++++++++++++++++++++-----------------
 lib/packets.h   |  3 +++
 2 files changed, 27 insertions(+), 17 deletions(-)

diff --git a/lib/conntrack.c b/lib/conntrack.c
index 48c54d3..d874551 100644
--- a/lib/conntrack.c
+++ b/lib/conntrack.c
@@ -1712,9 +1712,10 @@ check_l4_icmp6(const struct conn_key *key, const void *data, size_t size,
 }
 
 static inline bool
-extract_l4_tcp(struct conn_key *key, const void *data, size_t size)
+extract_l4_tcp(struct conn_key *key, const void *data, size_t size,
+               size_t *chk_len)
 {
-    if (OVS_UNLIKELY(size < TCP_HEADER_LEN)) {
+    if (OVS_UNLIKELY(size < (chk_len ? *chk_len : TCP_HEADER_LEN))) {
         return false;
     }
 
@@ -1727,9 +1728,10 @@ extract_l4_tcp(struct conn_key *key, const void *data, size_t size)
 }
 
 static inline bool
-extract_l4_udp(struct conn_key *key, const void *data, size_t size)
+extract_l4_udp(struct conn_key *key, const void *data, size_t size,
+               size_t *chk_len)
 {
-    if (OVS_UNLIKELY(size < UDP_HEADER_LEN)) {
+    if (OVS_UNLIKELY(size < (chk_len ? *chk_len : UDP_HEADER_LEN))) {
         return false;
     }
 
@@ -1743,7 +1745,7 @@ extract_l4_udp(struct conn_key *key, const void *data, size_t size)
 
 static inline bool extract_l4(struct conn_key *key, const void *data,
                               size_t size, bool *related, const void *l3,
-                              bool validate_checksum);
+                              bool validate_checksum, size_t *chk_len);
 
 static uint8_t
 reverse_icmp_type(uint8_t type)
@@ -1775,9 +1777,9 @@ reverse_icmp_type(uint8_t type)
  * possible */
 static inline int
 extract_l4_icmp(struct conn_key *key, const void *data, size_t size,
-                bool *related)
+                bool *related, size_t *chk_len)
 {
-    if (OVS_UNLIKELY(size < ICMP_HEADER_LEN)) {
+    if (OVS_UNLIKELY(size < (chk_len ? *chk_len : ICMP_HEADER_LEN))) {
         return false;
     }
 
@@ -1828,8 +1830,9 @@ extract_l4_icmp(struct conn_key *key, const void *data, size_t size,
         key->src = inner_key.src;
         key->dst = inner_key.dst;
         key->nw_proto = inner_key.nw_proto;
+        size_t check_len = ICMP_ERROR_DATA_L4_LEN;
 
-        ok = extract_l4(key, l4, tail - l4, NULL, l3, false);
+        ok = extract_l4(key, l4, tail - l4, NULL, l3, false, &check_len);
         if (ok) {
             conn_key_reverse(key);
             *related = true;
@@ -1916,7 +1919,7 @@ extract_l4_icmp6(struct conn_key *key, const void *data, size_t size,
         key->dst = inner_key.dst;
         key->nw_proto = inner_key.nw_proto;
 
-        ok = extract_l4(key, l4, tail - l4, NULL, l3, false);
+        ok = extract_l4(key, l4, tail - l4, NULL, l3, false, NULL);
         if (ok) {
             conn_key_reverse(key);
             *related = true;
@@ -1941,26 +1944,29 @@ extract_l4_icmp6(struct conn_key *key, const void *data, size_t size,
  * an ICMP or ICMP6 header.
  *
  * If 'related' is NULL, it means that we're already parsing a header nested
- * in an ICMP error.  In this case, we skip checksum and length validation. */
+ * in an ICMP error.  In this case, we skip the checksum and some length
+ * validations. */
 static inline bool
 extract_l4(struct conn_key *key, const void *data, size_t size, bool *related,
-           const void *l3, bool validate_checksum)
+           const void *l3, bool validate_checksum, size_t *chk_len)
 {
     if (key->nw_proto == IPPROTO_TCP) {
         return (!related || check_l4_tcp(key, data, size, l3,
-                validate_checksum)) && extract_l4_tcp(key, data, size);
+                validate_checksum))
+               && extract_l4_tcp(key, data, size, chk_len);
     } else if (key->nw_proto == IPPROTO_UDP) {
         return (!related || check_l4_udp(key, data, size, l3,
-                validate_checksum)) && extract_l4_udp(key, data, size);
+                validate_checksum))
+               && extract_l4_udp(key, data, size, chk_len);
     } else if (key->dl_type == htons(ETH_TYPE_IP)
                && key->nw_proto == IPPROTO_ICMP) {
         return (!related || check_l4_icmp(data, size, validate_checksum))
-               && extract_l4_icmp(key, data, size, related);
+               && extract_l4_icmp(key, data, size, related, chk_len);
     } else if (key->dl_type == htons(ETH_TYPE_IPV6)
                && key->nw_proto == IPPROTO_ICMPV6) {
         return (!related || check_l4_icmp6(key, data, size, l3,
-                validate_checksum)) && extract_l4_icmp6(key, data, size,
-                related);
+                validate_checksum))
+               && extract_l4_icmp6(key, data, size, related);
     } else {
         return false;
     }
@@ -2039,7 +2045,8 @@ conn_key_extract(struct conntrack *ct, struct dp_packet *pkt, ovs_be16 dl_type,
             bool  hwol_good_l4_csum = dp_packet_l4_checksum_valid(pkt);
             /* Validate the checksum only when hwol is not supported. */
             if (extract_l4(&ctx->key, l4, dp_packet_l4_size(pkt),
-                           &ctx->icmp_related, l3, !hwol_good_l4_csum)) {
+                           &ctx->icmp_related, l3, !hwol_good_l4_csum,
+                           NULL)) {
                 ctx->hash = conn_key_hash(&ctx->key, ct->hash_basis);
                 return true;
             }
diff --git a/lib/packets.h b/lib/packets.h
index 69caa78..5c3a8a7 100644
--- a/lib/packets.h
+++ b/lib/packets.h
@@ -741,6 +741,9 @@ struct icmp_header {
 };
 BUILD_ASSERT_DECL(ICMP_HEADER_LEN == sizeof(struct icmp_header));
 
+/* ICMPV4 */
+#define ICMP_ERROR_DATA_L4_LEN 8
+
 #define IGMP_HEADER_LEN 8
 struct igmp_header {
     uint8_t igmp_type;
-- 
1.9.1



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