Staging: exfat: Avoid use of strcpy

Use strscpy instead of strcpy in exfat_core.c, and add a check
for length that will return already known FFS_INVALIDPATH.
Suggested-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Sandro Volery <sandro@volery.com>
Reviewed-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/20190912082559.GA5043@volerySigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/exfat/exfat_core.c

@@ -2961,11 +2961,9 @@ s32 resolve_path(struct inode *inode, char *path, struct chain_t *p_dir,
 	struct fs_info_t *p_fs = &(EXFAT_SB(sb)->fs_info);
 	struct file_id_t *fid = &(EXFAT_I(inode)->fid);
 
-	if (strlen(path) >= (MAX_NAME_LENGTH * MAX_CHARSET_SIZE))
+	if (strscpy(name_buf, path, sizeof(name_buf)) < 0)
 		return FFS_INVALIDPATH;
 
-	strcpy(name_buf, path);
-
 	nls_cstring_to_uniname(sb, p_uniname, name_buf, &lossy);
 	if (lossy)
 		return FFS_INVALIDPATH;