xfs: lift cursor copy in/out into xfs_ioc_attr_list

Lift the common code to copy the cursor from and to user space into
xfs_ioc_attr_list.  Note that this means we copy in twice now as
the cursor is in the middle of the conaining structure, but we never
touch the memory for the original copy.  Doing so keeps the cursor
handling isolated in the common helper.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Chandan Rajendra <chandanrlinux@gmail.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

fs/xfs/xfs_ioctl.c

@@ -355,9 +355,10 @@ xfs_ioc_attr_list(
 	void __user			*ubuf,
 	int				bufsize,
 	int				flags,
-	struct attrlist_cursor_kern	*cursor)
+	struct xfs_attrlist_cursor __user *ucursor)
 {
 	struct xfs_attr_list_context	context;
+	struct attrlist_cursor_kern	cursor;
 	struct xfs_attrlist		*alist;
 	void				*buffer;
 	int				error;
@@ -377,10 +378,12 @@ xfs_ioc_attr_list(
 	/*
 	 * Validate the cursor.
 	 */
-	if (cursor->pad1 || cursor->pad2)
+	if (copy_from_user(&cursor, ucursor, sizeof(cursor)))
+		return -EFAULT;
+	if (cursor.pad1 || cursor.pad2)
 		return -EINVAL;
-	if ((cursor->initted == 0) &&
-	    (cursor->hashval || cursor->blkno || cursor->offset))
+	if ((cursor.initted == 0) &&
+	    (cursor.hashval || cursor.blkno || cursor.offset))
 		return -EINVAL;
 
 	buffer = kmem_zalloc_large(bufsize, 0);
@@ -392,7 +395,7 @@ xfs_ioc_attr_list(
 	 */
 	memset(&context, 0, sizeof(context));
 	context.dp = dp;
-	context.cursor = cursor;
+	context.cursor = &cursor;
 	context.resynch = 1;
 	context.flags = flags;
 	context.buffer = buffer;
@@ -409,7 +412,8 @@ xfs_ioc_attr_list(
 	if (error)
 		goto out_free;
 
-	if (copy_to_user(ubuf, buffer, bufsize))
+	if (copy_to_user(ubuf, buffer, bufsize) ||
+	    copy_to_user(ucursor, &cursor, sizeof(cursor)))
 		error = -EFAULT;
 out_free:
 	kmem_free(buffer);
@@ -419,33 +423,23 @@ xfs_ioc_attr_list(
 STATIC int
 xfs_attrlist_by_handle(
 	struct file		*parfilp,
-	void			__user *arg)
+	struct xfs_fsop_attrlist_handlereq __user *p)
 {
-	int			error = -ENOMEM;
-	attrlist_cursor_kern_t	*cursor;
-	struct xfs_fsop_attrlist_handlereq __user	*p = arg;
-	xfs_fsop_attrlist_handlereq_t al_hreq;
+	struct xfs_fsop_attrlist_handlereq al_hreq;
 	struct dentry		*dentry;
+	int			error = -ENOMEM;
 
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
-	if (copy_from_user(&al_hreq, arg, sizeof(xfs_fsop_attrlist_handlereq_t)))
+	if (copy_from_user(&al_hreq, p, sizeof(al_hreq)))
 		return -EFAULT;
 
 	dentry = xfs_handlereq_to_dentry(parfilp, &al_hreq.hreq);
 	if (IS_ERR(dentry))
 		return PTR_ERR(dentry);
 
-	cursor = (attrlist_cursor_kern_t *)&al_hreq.pos;
 	error = xfs_ioc_attr_list(XFS_I(d_inode(dentry)), al_hreq.buffer,
-				  al_hreq.buflen, al_hreq.flags, cursor);
-	if (error)
-		goto out_dput;
-
-	if (copy_to_user(&p->pos, cursor, sizeof(attrlist_cursor_kern_t)))
-		error = -EFAULT;
-
-out_dput:
+				  al_hreq.buflen, al_hreq.flags, &p->pos);
 	dput(dentry);
 	return error;
 }

fs/xfs/xfs_ioctl.h

@@ -40,7 +40,7 @@ int xfs_ioc_attrmulti_one(struct file *parfilp, struct inode *inode,
 		uint32_t opcode, void __user *uname, void __user *value,
 		uint32_t *len, uint32_t flags);
 int xfs_ioc_attr_list(struct xfs_inode *dp, void __user *ubuf, int bufsize,
-	int flags, struct attrlist_cursor_kern *cursor);
+	int flags, struct xfs_attrlist_cursor __user *ucursor);
 
 extern struct dentry *
 xfs_handle_to_dentry(

fs/xfs/xfs_ioctl32.c

@@ -352,35 +352,24 @@ xfs_compat_handlereq_to_dentry(
 STATIC int
 xfs_compat_attrlist_by_handle(
 	struct file		*parfilp,
-	void			__user *arg)
+	compat_xfs_fsop_attrlist_handlereq_t __user *p)
 {
-	int			error;
-	attrlist_cursor_kern_t	*cursor;
-	compat_xfs_fsop_attrlist_handlereq_t __user *p = arg;
 	compat_xfs_fsop_attrlist_handlereq_t al_hreq;
 	struct dentry		*dentry;
+	int			error;
 
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
-	if (copy_from_user(&al_hreq, arg,
-			   sizeof(compat_xfs_fsop_attrlist_handlereq_t)))
+	if (copy_from_user(&al_hreq, p, sizeof(al_hreq)))
 		return -EFAULT;
 
 	dentry = xfs_compat_handlereq_to_dentry(parfilp, &al_hreq.hreq);
 	if (IS_ERR(dentry))
 		return PTR_ERR(dentry);
 
-	cursor = (attrlist_cursor_kern_t *)&al_hreq.pos;
 	error = xfs_ioc_attr_list(XFS_I(d_inode(dentry)),
 			compat_ptr(al_hreq.buffer), al_hreq.buflen,
-			al_hreq.flags, cursor);
-	if (error)
-		goto out_dput;
-
-	if (copy_to_user(&p->pos, cursor, sizeof(attrlist_cursor_kern_t)))
-		error = -EFAULT;
-
-out_dput:
+			al_hreq.flags, &p->pos);
 	dput(dentry);
 	return error;
 }