[PATCH AUTOSEL 3.18 92/98] ovl: fix open in stacked overlay

[Sasha Levin]

From: Miklos Szeredi <miklos@xxxxxxxxxx>

[ Upstream commit 1c8a47df36d72ace8cf78eb6c228aa0f8027d3c2 ]

If two overlayfs filesystems are stacked on top of each other, then we need
recursion in ovl_d_select_inode().

I guess d_backing_inode() is supposed to do that.  But currently it doesn't
and that functionality is open coded in vfs_open().  This is now copied
into ovl_d_select_inode() to fix this regression.

Reported-by: Alban Crequy <alban.crequy@xxxxxxxxx>
Signed-off-by: Miklos Szeredi <miklos@xxxxxxxxxx>
Fixes: 4bacc9c9234c ("overlayfs: Make f_path always point to the overlay...")
Cc: David Howells <dhowells@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # v4.2+
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 fs/overlayfs/inode.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index df5c2853c4e5..a01ec1836a72 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -377,6 +377,9 @@ struct inode *ovl_d_select_inode(struct dentry *dentry, unsigned file_flags)
 		ovl_path_upper(dentry, &realpath);
 	}
 
+	if (realpath.dentry->d_flags & DCACHE_OP_SELECT_INODE)
+		return realpath.dentry->d_op->d_select_inode(realpath.dentry, file_flags);
+
 	return d_backing_inode(realpath.dentry);
 }
 
-- 
2.17.1