Staging: bcm: Add size maximum size restrictions for IOCTL_IDLE_REQ

In the first alteration, the MAX_CNTL_PKT_SIZE is the
maximum size of the control packet in ->Adapter->txctlpacket[]
which is defined in InitAdapter(). This caps the size of
kmalloc memory allocation. In the second change, this max
cap fixes a potential memory corruption bug when subsequent
memset and memcpy calls are invoked.
Signed-off-by: Kevin McKinney <klmckinney1@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/bcm/Bcmchar.c

@@ -690,6 +690,9 @@ static long bcm_char_ioctl(struct file *filp, UINT cmd, ULONG arg)
 		if (IoBuffer.InputLength < sizeof(struct link_request))
 			return -EINVAL;
 
+		if (IoBuffer.InputLength > MAX_CNTL_PKT_SIZE)
+			return -EINVAL;
+
 		pvBuffer = kmalloc(IoBuffer.InputLength, GFP_KERNEL);
 		if (!pvBuffer)
 			return -ENOMEM;

drivers/staging/bcm/Misc.c

@@ -421,6 +421,10 @@ INT CopyBufferToControlPacket(PMINI_ADAPTER Adapter,/**<Logical Adapter*/
 				pLeader->PLength = pktlen;
 			}
 		}
+
+		if (pktlen + LEADER_SIZE > MAX_CNTL_PKT_SIZE)
+			return -EINVAL;
+
 		memset(ctrl_buff, 0, pktlen+LEADER_SIZE);
 		BCM_DEBUG_PRINT(Adapter,DBG_TYPE_TX, TX_CONTROL, DBG_LVL_ALL, "Copying the Control Packet Buffer with length=%d\n", pLeader->PLength);
 		*(PLEADER)ctrl_buff=*pLeader;