Staging: bcm: Check correct user provided length and fix error code returned

bcm driver copies a buffer length provided by userpace without checking it.

RxCntrlMsgBitMask is of type unsigned long so only makes sense to copy
sizeof(unsigned long) bytes.

Also, copy_from_user() returns the number of bytes that could not be copied.
The driver is returning that value as error code instead of -EFAULT.

This patch solves both issues.
Signed-off-by: Javier Martinez Canillas <martinez.javier@gmail.com>
Cc: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/bcm/Bcmchar.c

@@ -2024,6 +2024,12 @@ static long bcm_char_ioctl(struct file *filp, UINT cmd, ULONG arg)
 				if(Status)
 				{
 					BCM_DEBUG_PRINT(Adapter,DBG_TYPE_OTHERS, OSAL_DBG, DBG_LVL_ALL,"copy of Ioctl buffer is failed from user space");
+					Status = -EFAULT;
+					break;
+				}
+
+				if (IoBuffer.InputLength != sizeof(unsigned long)) {
+					Status = -EINVAL;
 					break;
 				}
 
@@ -2031,6 +2037,7 @@ static long bcm_char_ioctl(struct file *filp, UINT cmd, ULONG arg)
 				if(Status)
 				{
 					BCM_DEBUG_PRINT(Adapter,DBG_TYPE_OTHERS, OSAL_DBG, DBG_LVL_ALL,"copy of control bit mask failed from user space");
+					Status = -EFAULT;
 					break;
 				}
 				BCM_DEBUG_PRINT(Adapter,DBG_TYPE_OTHERS, OSAL_DBG, DBG_LVL_ALL,"\n Got user defined cntrl msg bit mask :%lx", RxCntrlMsgBitMask);