linux-kernel - Re: [PATCH 01/11] media: tm6000: fix potential Spectre variant 1

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Message-ID: <20180515141655.idzuh2jfdkuu5grs@mwanda>
Date:   Tue, 15 May 2018 17:16:55 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Mauro Carvalho Chehab <mchehab+samsung@...nel.org>
Cc:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 01/11] media: tm6000: fix potential Spectre variant 1

On Tue, May 15, 2018 at 08:59:53AM -0300, Mauro Carvalho Chehab wrote:
> Em Mon, 14 May 2018 22:31:37 -0500
> "Gustavo A. R. Silva" <gustavo@...eddedor.com> escreveu:
> 
> > Hi Mauro,
> > 
> > On 04/26/2018 06:42 PM, Mauro Carvalho Chehab wrote:
> > 
> > >>
> > >> I noticed you changed the status of this series from rejected to new.
> > > 
> > > Yes.
> > > 
> > >> Also, there are other similar issues in media/pci/
> > > 
> > > Well, the issues will be there everywhere on all media drivers.
> > > 
> > > I marked your patches because I need to study it carefully, after
> > > Peter's explanations. My plan is to do it next week. Still not
> > > sure if the approach you took is the best one or not.
> > > 
> > > As I said, one possibility is to change the way v4l2-core handles
> > > VIDIOC_ENUM_foo ioctls, but that would be make harder to -stable
> > > backports.
> > > 
> > > I need a weekend to sleep on it.
> > > 
> > 
> > I'm curious about how you finally resolved to handle these issues.
> > 
> > I noticed Smatch is no longer reporting them.
> 
> There was no direct fix for it, but maybe this patch has something
> to do with the smatch error report cleanup:
> 
> commit 3ad3b7a2ebaefae37a7eafed0779324987ca5e56
> Author: Sami Tolvanen <samitolvanen@...gle.com>
> Date:   Tue May 8 13:56:12 2018 -0400
> 
>     media: v4l2-ioctl: replace IOCTL_INFO_STD with stub functions
>     
>     This change removes IOCTL_INFO_STD and adds stub functions where
>     needed using the DEFINE_V4L_STUB_FUNC macro. This fixes indirect call
>     mismatches with Control-Flow Integrity, caused by calling standard
>     ioctls using a function pointer that doesn't match the function type.
>     
>     Signed-off-by: Sami Tolvanen <samitolvanen@...gle.com>
>     Signed-off-by: Hans Verkuil <hansverk@...co.com>
>     Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@...nel.org>
> 

Possibly...  There was an ancient bug in Smatch's function pointer
handling.  I just pushed a fix for it now so the warning is there on
linux-next.

regards,
dan carpenter