linux-kernel - Re: [RFC PATCH 04/13] vfio/mdev: remove the usage of the list iterator after the loop

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Date:   Fri, 18 Feb 2022 11:12:16 -0400
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Jakob Koschel <jakobkoschel@...il.com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Arnd Bergman <arnd@...db.de>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Kees Cook <keescook@...omium.org>,
        Mike Rapoport <rppt@...nel.org>,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        Brian Johannesmeyer <bjohannesmeyer@...il.com>,
        Cristiano Giuffrida <c.giuffrida@...nl>,
        "Bos, H.J." <h.j.bos@...nl>
Subject: Re: [RFC PATCH 04/13] vfio/mdev: remove the usage of the list
 iterator after the loop

On Thu, Feb 17, 2022 at 07:48:20PM +0100, Jakob Koschel wrote:
> It is unsafe to assume that tmp != mdev can only evaluate to false
> if the break within the list iterator is hit.
> 
> When the break is not hit, tmp is set to an address derived from the
> head element. If mdev would match with that value of tmp it would allow
> continuing beyond the safety check even if mdev was never found within
> the list

I think due to other construction this is not actually possible, but I
guess it is technically correct

This seems like just a straight up style fix with nothing to do with
speculative execution though. Why not just send it as a proper patch?

Jason