Return-Path: Received: from mail-pf0-f180.google.com ([209.85.192.180]:33345 "EHLO mail-pf0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754853AbdDEP3Q (ORCPT ); Wed, 5 Apr 2017 11:29:16 -0400 Received: by mail-pf0-f180.google.com with SMTP id s16so9066934pfs.0 for ; Wed, 05 Apr 2017 08:29:16 -0700 (PDT) Date: Wed, 5 Apr 2017 08:29:14 -0700 From: Kees Cook To: linux-kernel@vger.kernel.org Cc: NeilBrown , Trond Myklebust , Anna Schumaker , linux-nfs@vger.kernel.org Subject: [PATCH v2] NFS: Avoid cross-structure casting Message-ID: <20170405152914.GA57260@beast> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-nfs-owner@vger.kernel.org List-ID: When the call to nfs_devname() fails, the error path attempts to retain the error via the mnt variable, but this requires a cast across very different types (char * to struct vfsmount *), which the upcoming structure layout randomization plugin flags as being potentially dangerous in the face of randomization. This is a false positive, but what this code actually wants to do is retain the error value, so this patch explicitly sets it, instead of using what seems to be an unexpected cast. Signed-off-by: Kees Cook --- v2: duh, use ERR_CAST. thanks neilb! --- fs/nfs/namespace.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/fs/nfs/namespace.c b/fs/nfs/namespace.c index 786f17580582..8ca5d147124d 100644 --- a/fs/nfs/namespace.c +++ b/fs/nfs/namespace.c @@ -259,9 +259,10 @@ struct vfsmount *nfs_do_submount(struct dentry *dentry, struct nfs_fh *fh, if (page == NULL) goto out; devname = nfs_devname(dentry, page, PAGE_SIZE); - mnt = (struct vfsmount *)devname; - if (IS_ERR(devname)) + if (IS_ERR(devname)) { + mnt = ERR_CAST(devname); goto free_page; + } mnt = nfs_do_clone_mount(NFS_SB(dentry->d_sb), devname, &mountdata); free_page: free_page((unsigned long)page); -- 2.7.4 -- Kees Cook Pixel Security