linux-kernel - Re: [PATCH v2 07/15] vsock/virtio: fix DMA alignment for event

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: Windows password security audit tool. GUI, reports in PDF.

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

Message-ID: <aV-4mPQYn3MUW10A@sgarzare-redhat>
Date: Thu, 8 Jan 2026 15:04:07 +0100
From: Stefano Garzarella <sgarzare@...hat.com>
To: "Michael S. Tsirkin" <mst@...hat.com>
Cc: linux-kernel@...r.kernel.org, Cong Wang <xiyou.wangcong@...il.com>, 
	Jonathan Corbet <corbet@....net>, Olivia Mackall <olivia@...enic.com>, 
	Herbert Xu <herbert@...dor.apana.org.au>, Jason Wang <jasowang@...hat.com>, 
	Paolo Bonzini <pbonzini@...hat.com>, Stefan Hajnoczi <stefanha@...hat.com>, 
	Eugenio Pérez <eperezma@...hat.com>, "James E.J. Bottomley" <James.Bottomley@...senpartnership.com>, 
	"Martin K. Petersen" <martin.petersen@...cle.com>, Gerd Hoffmann <kraxel@...hat.com>, 
	Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, Marek Szyprowski <m.szyprowski@...sung.com>, 
	Robin Murphy <robin.murphy@....com>, "David S. Miller" <davem@...emloft.net>, 
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>, 
	Petr Tesarik <ptesarik@...e.com>, Leon Romanovsky <leon@...nel.org>, 
	Jason Gunthorpe <jgg@...pe.ca>, Bartosz Golaszewski <brgl@...nel.org>, linux-doc@...r.kernel.org, 
	linux-crypto@...r.kernel.org, virtualization@...ts.linux.dev, linux-scsi@...r.kernel.org, 
	iommu@...ts.linux.dev, kvm@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH v2 07/15] vsock/virtio: fix DMA alignment for event_list

On Mon, Jan 05, 2026 at 03:23:17AM -0500, Michael S. Tsirkin wrote:
>On non-cache-coherent platforms, when a structure contains a buffer
>used for DMA alongside fields that the CPU writes to, cacheline sharing
>can cause data corruption.
>
>The event_list array is used for DMA_FROM_DEVICE operations via
>virtqueue_add_inbuf(). The adjacent event_run and guest_cid fields are
>written by the CPU while the buffer is available, so mapped for the
>device. If these share cachelines with event_list, CPU writes can
>corrupt DMA data.
>
>Add __dma_from_device_group_begin()/end() annotations to ensure event_list
>is isolated in its own cachelines.
>
>Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
>---
> net/vmw_vsock/virtio_transport.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
>diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c
>index 8c867023a2e5..bb94baadfd8b 100644
>--- a/net/vmw_vsock/virtio_transport.c
>+++ b/net/vmw_vsock/virtio_transport.c
>@@ -17,6 +17,7 @@
> #include <linux/virtio_ids.h>
> #include <linux/virtio_config.h>
> #include <linux/virtio_vsock.h>
>+#include <linux/dma-mapping.h>
> #include <net/sock.h>
> #include <linux/mutex.h>
> #include <net/af_vsock.h>
>@@ -59,8 +60,9 @@ struct virtio_vsock {
> 	 */
> 	struct mutex event_lock;
> 	bool event_run;
>+	__dma_from_device_group_begin();
> 	struct virtio_vsock_event event_list[8];
>-
>+	__dma_from_device_group_end();

Can we keep the blank line before `guest_cid` so that the comment before 
this section makes sense? (regarding the lock required to access these 
fields)

Thanks,
Stefano

> 	u32 guest_cid;
> 	bool seqpacket_allow;
>
>-- 
>MST
>