linux-kernel - Re: [PATCH v2 01/20] NFS: Avoid cross-structure casting

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Date:   Sun, 28 May 2017 00:53:13 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     kernel-hardening@...ts.openwall.com,
        Laura Abbott <labbott@...hat.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 01/20] NFS: Avoid cross-structure casting

On Fri, May 26, 2017 at 01:17:05PM -0700, Kees Cook wrote:
> 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 <keescook@...omium.org>
> Acked-by: Trond Myklebust <trond.myklebust@...marydata.com>

Looks good:

Reviewed-by: Christoph Hellwig <hch@....de>

And I think we should get this (and the other cast patches) in ASAP,
independent of the fat of the randstruct plugin.