[PATCH v4 5/6] ovl: remove privs in ovl_copyfile()

[Christian Brauner <brauner@xxxxxxxxxx>]

From: Amir Goldstein <amir73il@xxxxxxxxx>

Underlying fs doesn't remove privs because copy_range/remap_range are
called with privileged mounter credentials.

This fixes some failures in fstest generic/673.

Fixes: 8ede205541ff ("ovl: add reflink/copyfile/dedup support")
Acked-by: Miklos Szeredi <mszeredi@xxxxxxxxxx>
Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
---

Notes:
    /* v2 */
    Acked-by: Miklos Szeredi <miklos@xxxxxxxxxx>
    
    /* v3 */
    unchanged
    
    /* v4 */
    unchanged

 fs/overlayfs/file.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
index a1a22f58ba18..755a11c63596 100644
--- a/fs/overlayfs/file.c
+++ b/fs/overlayfs/file.c
@@ -567,14 +567,23 @@ static loff_t ovl_copyfile(struct file *file_in, loff_t pos_in,
 	const struct cred *old_cred;
 	loff_t ret;
 
+	inode_lock(inode_out);
+	if (op != OVL_DEDUPE) {
+		/* Update mode */
+		ovl_copyattr(inode_out);
+		ret = file_remove_privs(file_out);
+		if (ret)
+			goto out_unlock;
+	}
+
 	ret = ovl_real_fdget(file_out, &real_out);
 	if (ret)
-		return ret;
+		goto out_unlock;
 
 	ret = ovl_real_fdget(file_in, &real_in);
 	if (ret) {
 		fdput(real_out);
-		return ret;
+		goto out_unlock;
 	}
 
 	old_cred = ovl_override_creds(file_inode(file_out)->i_sb);
@@ -603,6 +612,9 @@ static loff_t ovl_copyfile(struct file *file_in, loff_t pos_in,
 	fdput(real_in);
 	fdput(real_out);
 
+out_unlock:
+	inode_unlock(inode_out);
+
 	return ret;
 }
 
-- 
2.34.1