ovl: fix open in stacked overlay

[ 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@gmail.com>
Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Fixes: 4bacc9c9234c ("overlayfs: Make f_path always point to the overlay...")
Cc: David Howells <dhowells@redhat.com>
Cc: <stable@vger.kernel.org> # v4.2+
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index df5c2853c4e58d4354be264d228d7be39127112f..a01ec1836a724953ec97c53f5615a3870ed0bee9 100644 (file)
--- 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);
 }