[PATCH V2 4/4] net/colo.c: fix segmentation fault when packet is not parsed correctly

[Zhang Chen]

When COLO use only one vnet_hdr_support parameter between
filter-redirector and filter-mirror(or colo-compare), COLO will crash
with segmentation fault. Back track as follow:

Thread 1 "qemu-system-x86" received signal SIGSEGV, Segmentation fault.
0x0000555555cb200b in eth_get_l2_hdr_length (p=0x0)
    at /home/tao/project/COLO/colo-qemu/include/net/eth.h:296
296         uint16_t proto = be16_to_cpu(PKT_GET_ETH_HDR(p)->h_proto);
(gdb) bt
0  0x0000555555cb200b in eth_get_l2_hdr_length (p=0x0)
    at /home/tao/project/COLO/colo-qemu/include/net/eth.h:296
1  0x0000555555cb22b4 in parse_packet_early (pkt=0x555556a44840) at
net/colo.c:49
2  0x0000555555cb2b91 in is_tcp_packet (pkt=0x555556a44840) at
net/filter-rewriter.c:63

So wrong vnet_hdr_len will cause pkt->data become NULL. Add check to
raise error and add trace-events to track vnet_hdr_len.

Signed-off-by: Tao Xu <tao3.xu@intel.com>
Signed-off-by: Zhang Chen <chen.zhang@intel.com>
Reviewed-by: Li Zhijian <lizhijian@fujitsu.com>
---
 net/colo.c       | 9 ++++++++-
 net/trace-events | 1 +
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/net/colo.c b/net/colo.c
index 694f3c93ef..6b0ff562ad 100644
--- a/net/colo.c
+++ b/net/colo.c
@@ -46,7 +46,14 @@ int parse_packet_early(Packet *pkt)
     static const uint8_t vlan[] = {0x81, 0x00};
     uint8_t *data = pkt->data + pkt->vnet_hdr_len;
     uint16_t l3_proto;
-    ssize_t l2hdr_len = eth_get_l2_hdr_length(data);
+    ssize_t l2hdr_len;
+
+    if (data == NULL) {
+        trace_colo_proxy_main_vnet_info("This packet is not parsed correctly, "
+                                        "pkt->vnet_hdr_len", 
pkt->vnet_hdr_len);
+        return 1;
+    }
+    l2hdr_len = eth_get_l2_hdr_length(data);
 
     if (pkt->size < ETH_HLEN + pkt->vnet_hdr_len) {
         trace_colo_proxy_main("pkt->size < ETH_HLEN");
diff --git a/net/trace-events b/net/trace-events
index d7a17256cc..6af927b4b9 100644
--- a/net/trace-events
+++ b/net/trace-events
@@ -9,6 +9,7 @@ vhost_user_event(const char *chr, int event) "chr: %s got 
event: %d"
 
 # colo.c
 colo_proxy_main(const char *chr) ": %s"
+colo_proxy_main_vnet_info(const char *sta, int size) ": %s = %d"
 
 # colo-compare.c
 colo_compare_main(const char *chr) ": %s"
-- 
2.25.1