linux-kernel - Re: [PULL] vhost: cleanups and fixes

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Date:   Thu, 1 Nov 2018 16:06:19 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     mst@...hat.com, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        bijan.mottahedeh@...cle.com, gedwards@....com, joe@...ches.com,
        lenaic@...ard.fr, liang.z.li@...el.com, mhocko@...nel.org,
        mhocko@...e.com, stefanha@...hat.com, wei.w.wang@...el.com
Subject: Re: [PULL] vhost: cleanups and fixes

On Thu, Nov 1, 2018 at 4:00 PM Kees Cook <keescook@...omium.org> wrote:
>
> +       memset(&rsp, 0, sizeof(rsp));
> +       rsp.response = VIRTIO_SCSI_S_FUNCTION_REJECTED;
> +       resp = vq->iov[out].iov_base;
> +       ret = __copy_to_user(resp, &rsp, sizeof(rsp));
>
> Is it actually safe to trust that iov_base has passed an earlier
> access_ok() check here? Why not just use copy_to_user() instead?

Good point.

We really should have removed those double-underscore things ages ago.

Also, apart from the address, what about the size? Wouldn't it be
better to use copy_to_iter() rather than implement it badly by hand?

               Linus