staging: for dgrp, let nd_ps_desc always NUL terminated string within MAX_DESC_LEN length

Use strlcpy instead of strncpy to let nd_ps_desc always NUL terminated.

Change nd_ps_desc in nd_struct struct to MAX_DESC_LEN to avoid the
confusion (the related length checking also need be changed to
MAX_DESC_LEN - 1).

Signed-off-by: Chen Gang <gang.chen@asianux.com>
Acked-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/dgrp/dgrp_dpa_ops.c

@@ -392,7 +392,7 @@ static long dgrp_dpa_ioctl(struct file *file, unsigned int cmd,
 		getnode.nd_rx_byte = nd->nd_rx_byte;
 
 		memset(&getnode.nd_ps_desc, 0, MAX_DESC_LEN);
-		strncpy(getnode.nd_ps_desc, nd->nd_ps_desc, MAX_DESC_LEN);
+		strlcpy(getnode.nd_ps_desc, nd->nd_ps_desc, MAX_DESC_LEN);
 
 		if (copy_to_user(uarg, &getnode, sizeof(struct digi_node)))
 			return -EFAULT;

drivers/staging/dgrp/dgrp_net_ops.c

@@ -3083,7 +3083,7 @@ check_query:
 						nd->nd_hw_ver = (b[8] << 8) | b[9];
 						nd->nd_sw_ver = (b[10] << 8) | b[11];
 						nd->nd_hw_id = b[6];
-						desclen = ((plen - 12) > MAX_DESC_LEN) ? MAX_DESC_LEN :
+						desclen = (plen - 12 > MAX_DESC_LEN - 1) ? MAX_DESC_LEN - 1 :
 							plen - 12;
 
 						if (desclen <= 0) {

drivers/staging/dgrp/drp.h

@@ -674,7 +674,7 @@ struct nd_struct {
 	ushort	     nd_hw_ver;		  /* HW version returned from PS   */
 	ushort	     nd_sw_ver;		  /* SW version returned from PS   */
 	uint	     nd_hw_id;		  /* HW ID returned from PS	   */
-	u8	  nd_ps_desc[MAX_DESC_LEN+1];  /* Description from PS	*/
+	u8	  nd_ps_desc[MAX_DESC_LEN];  /* Description from PS	*/
 	uint	     nd_vpd_len;		/* VPD len, if any */
 	u8	     nd_vpd[VPDSIZE];		/* VPD, if any */