staging: exfat: Use kmemdup in exfat_symlink()

Use kmemdup rather than duplicating its implementation
Signed-off-by: NYueHaibing <yuehaibing@huawei.com>
Link: https://lore.kernel.org/r/20190905030047.88401-1-yuehaibing@huawei.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/exfat/exfat_super.c

@@ -2706,12 +2706,11 @@ static int exfat_symlink(struct inode *dir, struct dentry *dentry,
 	inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
 	/* timestamp is already written, so mark_inode_dirty() is unneeded. */
 
-	EXFAT_I(inode)->target = kmalloc(len+1, GFP_KERNEL);
+	EXFAT_I(inode)->target = kmemdup(target, len + 1, GFP_KERNEL);
 	if (!EXFAT_I(inode)->target) {
 		err = -ENOMEM;
 		goto out;
 	}
-	memcpy(EXFAT_I(inode)->target, target, len+1);
 
 	dentry->d_time = GET_IVERSION(dentry->d_parent->d_inode);
 	d_instantiate(dentry, inode);