Date:   Fri, 7 Oct 2022 07:17:41 +0200
From:   Juergen Gross <jgross@...e.com>
To:     "M. Vefa Bicakci" <m.v.b@...box.com>,
        xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org
Cc:     Stefano Stabellini <sstabellini@...nel.org>,
        Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>,
        Demi Marie Obenour <demi@...isiblethingslab.com>,
        Gerd Hoffmann <kraxel@...hat.com>
Subject: Re: [PATCH v2 0/2] xen/gntdev: Fixes for leaks and VMA splitting

On 03.10.22 00:20, M. Vefa Bicakci wrote:
> Hi all,
> 
> First of all, sorry for the delay!
> 
> These patches continue the code review for the following patches:
>    https://lore.kernel.org/xen-devel/20220912040002.198191-1-m.v.b@runbox.com/t/#u
> 
> The original description of the patch set is as follows:
> 
>    "The changes in this patch series intend to fix the Xen grant device
>    driver, so that grant mapping leaks caused by partially failed grant
>    mapping operations are avoided with the first patch, and so that the
>    splitting of VMAs does not result in incorrectly unmapped grant pages
>    with the second patch. The second patch also prevents a similar issue
>    in a double-mapping scenario, where mmap() is used with MAP_FIXED to
>    map grants over an existing mapping created with the same grants, and
>    where grant pages are unmapped incorrectly as well."
> 
> A summary of the changes from v1 is as follows:
> - Addressed Juergen's code review comment regarding the first patch.
> - Amended the description of the second patch to note that the described
>    issues are encountered with PV domains.
> 
> Verification notes:
> 
> - I have tested these commits on top of Linux v5.15.70 and v5.15.71, and
>    I verified that they compile successfully on top of the tag
>    "next-20220930", which corresponds to the base commit ID included at
>    the bottom of this e-mail.
> 
> - My tests consist of using a kernel with Qubes OS v4.1's patches and
>    these patches on my main computer for day-to-day tasks, in conjunction
>    with Qubes OS's version of the Xen hypervisor v4.14.5, with the latter
>    custom-compiled with CONFIG_DEBUG.
> 
> - I used a test program that verifies the following scenarios with an
>    unprivileged paravirtualized (PV) Xen domain:
> 
>    - A program mmap()s two pages from another Xen domain and munmap()s
>      the pages one by one. This used to result in implicit unmap errors
>      to be reported by Xen and a general protection fault to be triggered
>      by Xen in the affected domain, but now works as expected.
>    - A program mmap()s two pages from another Xen domain and then
>      attempts to remap (via MAP_FIXED) the same mapping again over the
>      same virtual address. This used to result in similar issues
>      (implicit unmap errors and general protection fault), but now is
>      rejected by the kernel.
>    - A program mmap()s two pages from another Xen domain and then
>      attempts to mmap() the same mapping again to a different virtual
>      address, by passing NULL as mmap()'s first argument. This used to be
>      rejected by the kernel, and it continues to be rejected by the
>      kernel.
> 
> - Unprivileged PVH Xen domains were also sanity tested with the same
>    test program. I should note that PVH domains worked as expected
>    without these patches too.
> 
> - Finally, I have verified that the original "g.e. 0x1234 still pending"
>    issue does not appear after rapidly resizing GUI windows in Qubes OS
>    v4.1.

Series pushed to xen/tip.git for-linus-6.1


Juergen


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