Linux-libre 4.4.3-gnu

1 files changed, 13 insertions, 0 deletions

diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index 4060ffde8..b29036aa8 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -42,6 +42,19 @@ int ovl_setattr(struct dentry *dentry, struct iattr *attr)
 	int err;
 	struct dentry *upperdentry;
 
+	/*
+	 * Check for permissions before trying to copy-up.  This is redundant
+	 * since it will be rechecked later by ->setattr() on upper dentry.  But
+	 * without this, copy-up can be triggered by just about anybody.
+	 *
+	 * We don't initialize inode->size, which just means that
+	 * inode_newsize_ok() will always check against MAX_LFS_FILESIZE and not
+	 * check for a swapfile (which this won't be anyway).
+	 */
+	err = inode_change_ok(dentry->d_inode, attr);
+	if (err)
+		return err;
+
 	err = ovl_want_write(dentry);
 	if (err)
 		goto out;