linux-kernel - Re: [PATCH] virtio-mmio: read[wl]()/write[wl] are already little-endian

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <60e83b80-f42b-456a-f37d-b7836e3abe1f@vivier.eu>
Date:   Thu, 11 Mar 2021 16:55:27 +0100
From:   Laurent Vivier <laurent@...ier.eu>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     linux-kernel@...r.kernel.org,
        virtualization@...ts.linux-foundation.org,
        Jason Wang <jasowang@...hat.com>
Subject: Re: [PATCH] virtio-mmio: read[wl]()/write[wl] are already
 little-endian

Le 11/03/2021 à 16:44, Michael S. Tsirkin a écrit :
> On Tue, Mar 09, 2021 at 11:43:13PM +0100, Laurent Vivier wrote:
>> read[wl]()/write[wl] already access memory in little-endian mode.
> 
> But then they convert it to CPU right? We just convert it back ...

Yes, you're right.

But there's a real problem with a big-endian guest using directly virtio-mmio without using virtio-pci.

It seems there is one too many little-endian conversion somewhere, and this has not been detected
before because there is no big-endian guest that uses virtio-mmio directly, and with little-endian
guests the conversion is a no-op. I'm going to have a closer look to the code path... perhaps the
problem is in QEMU not in the kernel.

Thanks,
Laurent