Add more check to make code more safely.

Signed-off-by: Eric Dong <eric.dong@intel.com>
Reviewed-by: Ouyang Qian  <ouyang.qian@intel.com>

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@13903 6f19259b-4bc3-4df7-8a09-765794883524

MdeModulePkg/Universal/Network/Ip4Dxe/Ip4Icmp.c

@@ -240,6 +240,7 @@ Ip4IcmpReplyEcho (
   // update is omitted.
   //
   Icmp                = (IP4_ICMP_QUERY_HEAD *) NetbufGetByte (Data, 0, NULL);
+  ASSERT (Icmp != NULL);
   Icmp->Head.Type     = ICMP_ECHO_REPLY;
   Icmp->Head.Checksum = 0;
   Icmp->Head.Checksum = (UINT16) (~NetblockChecksum ((UINT8 *) Icmp, Data->TotalSize));

MdeModulePkg/Universal/Network/Ip4Dxe/Ip4Input.c

@@ -849,7 +849,8 @@ Ip4AccpetFrame (
     goto DROP;
   }
 
-  Head      = (IP4_HEAD *) NetbufGetByte (Packet, 0, NULL); 
+  Head      = (IP4_HEAD *) NetbufGetByte (Packet, 0, NULL);
+  ASSERT (Head != NULL);
   OptionLen = (Head->HeadLen << 2) - IP4_MIN_HEADLEN;
   if (OptionLen > 0) {
     Option = (UINT8 *) (Head + 1);
@@ -899,6 +900,7 @@ Ip4AccpetFrame (
   // is transfered to the packet process logic.
   //
     Head = (IP4_HEAD *) NetbufGetByte (Packet, 0, NULL);
+    ASSERT (Head != NULL);
     Status = Ip4PreProcessPacket (
                IpSb,
                &Packet,

MdeModulePkg/Universal/Network/Mtftp4Dxe/Mtftp4Support.c

@@ -465,6 +465,7 @@ Mtftp4SendPacket (
   // to the connected port
   //
   Value = *((UINT16 *) NetbufGetByte (Packet, 0, NULL));
+  ASSERT (Value != NULL);
   OpCode = NTOHS (Value);
 
   if ((OpCode == EFI_MTFTP4_OPCODE_RRQ) || 
@@ -522,6 +523,7 @@ Mtftp4Retransmit (
   // Set the requests to the listening port, other packets to the connected port
   //
   Value = *(UINT16 *) NetbufGetByte (Instance->LastPacket, 0, NULL);
+  ASSERT (Value != NULL);
   OpCode = NTOHS (Value);
 
   if ((OpCode == EFI_MTFTP4_OPCODE_RRQ) || (OpCode == EFI_MTFTP4_OPCODE_DIR) ||

MdeModulePkg/Universal/Network/Tcp4Dxe/Tcp4Input.c

@@ -710,6 +710,7 @@ TcpInput (
   Tcb     = NULL;
 
   Head    = (TCP_HEAD *) NetbufGetByte (Nbuf, 0, NULL);
+  ASSERT (Head != NULL);
   Len     = Nbuf->TotalSize - (Head->HeadLen << 2);
 
   if ((Head->HeadLen < 5) || (Len < 0) ||
@@ -1422,6 +1423,7 @@ TcpIcmpInput (
   BOOLEAN          IcmpErrNotify;
 
   Head = (TCP_HEAD *) NetbufGetByte (Nbuf, 0, NULL);
+  ASSERT (Head != NULL);
   Tcb = TcpLocateTcb (
           Head->DstPort,
           Dst,

MdeModulePkg/Universal/Network/Tcp4Dxe/Tcp4Misc.c

@@ -592,6 +592,7 @@ TcpFormatNetbuf (
 
   Seg       = TCPSEG_NETBUF (Nbuf);
   Head      = (TCP_HEAD *) NetbufGetByte (Nbuf, 0, NULL);
+  ASSERT (Head != NULL);
   Nbuf->Tcp = Head;
 
   Seg->Seq  = NTOHL (Head->Seq);

MdeModulePkg/Universal/Network/Udp4Dxe/Udp4Impl.c

@@ -1612,6 +1612,7 @@ Udp4Demultiplex (
   // Get the datagram header from the packet buffer.
   //
   Udp4Header = (EFI_UDP_HEADER *) NetbufGetByte (Packet, 0, NULL);
+  ASSERT (Udp4Header != NULL);
 
   if (Udp4Header->Checksum != 0) {
     //
@@ -1799,6 +1800,7 @@ Udp4IcmpHandler (
   UDP4_INSTANCE_DATA     *Instance;
 
   Udp4Header = (EFI_UDP_HEADER *) NetbufGetByte (Packet, 0, NULL);
+  ASSERT (Udp4Header != NULL);
 
   CopyMem (&Udp4Session.SourceAddress, &NetSession->Source, sizeof (EFI_IPv4_ADDRESS));
   CopyMem (&Udp4Session.DestinationAddress, &NetSession->Dest, sizeof (EFI_IPv4_ADDRESS));