[Virtio-fs] [PATCH 1/2] overlayfs: ovl_setattr() should clear ATTR_FILE from attr->ia_valid

[Vivek Goyal]

ovl_setattr() can be passed an attr which has ATTR_FILE set and
attr->ia_file is a file pointer to overlay file. This is done
in open(O_TRUNC) path.

We should either replace with attr->ia_file with underlying file object
or clear ATTR_FILE so that underlying filesystem does not end up using
overlayfs file object pointer.

There are no good use cases yet so for now clear ATTR_FILE. fuse seems
to be one user which can use this. But it can work even without this.
So it is not mandatory to pass ATTR_FILE to fuse.

Signed-off-by: Vivek Goyal <vgoyal at redhat.com>
---
 fs/overlayfs/inode.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index b0d42ece4d7c..8d147bc70f0b 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -58,6 +58,11 @@ int ovl_setattr(struct dentry *dentry, struct iattr *attr)
 		if (attr->ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID))
 			attr->ia_valid &= ~ATTR_MODE;
 
+		/* We might have to translate ovl file into underlying file
+		 * object once some use cases are there. For now, simply
+		 * don't let underlying filesystem rely on attr->ia_file */
+		attr->ia_valid &= ~ATTR_FILE;
+
 		inode_lock(upperdentry->d_inode);
 		old_cred = ovl_override_creds(dentry->d_sb);
 		err = notify_change(upperdentry, attr, NULL);
-- 
2.25.3