linux-kernel - Re: [PATCH v2 01/10] vhost-scsi: protect vq->log

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Message-ID: <CACGkMEvDk-GzpVMPJPEJLRSrJjVHFsbXsd7LB9MjNEghbUc5pw@mail.gmail.com>
Date: Tue, 18 Mar 2025 08:47:41 +0800
From: Jason Wang <jasowang@...hat.com>
To: Dongli Zhang <dongli.zhang@...cle.com>
Cc: virtualization@...ts.linux.dev, kvm@...r.kernel.org, 
	netdev@...r.kernel.org, mst@...hat.com, michael.christie@...cle.com, 
	pbonzini@...hat.com, stefanha@...hat.com, eperezma@...hat.com, 
	joao.m.martins@...cle.com, joe.jin@...cle.com, si-wei.liu@...cle.com, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 01/10] vhost-scsi: protect vq->log_used with vq->mutex

On Tue, Mar 18, 2025 at 7:51 AM Dongli Zhang <dongli.zhang@...cle.com> wrote:
>
> The vhost-scsi completion path may access vq->log_base when vq->log_used is
> already set to false.
>
>     vhost-thread                       QEMU-thread
>
> vhost_scsi_complete_cmd_work()
> -> vhost_add_used()
>    -> vhost_add_used_n()
>       if (unlikely(vq->log_used))
>                                       QEMU disables vq->log_used
>                                       via VHOST_SET_VRING_ADDR.
>                                       mutex_lock(&vq->mutex);
>                                       vq->log_used = false now!
>                                       mutex_unlock(&vq->mutex);
>
>                                       QEMU gfree(vq->log_base)
>         log_used()
>         -> log_write(vq->log_base)
>
> Assuming the VMM is QEMU. The vq->log_base is from QEMU userpace and can be
> reclaimed via gfree(). As a result, this causes invalid memory writes to
> QEMU userspace.
>
> The control queue path has the same issue.
>
> Signed-off-by: Dongli Zhang <dongli.zhang@...cle.com>
> ---

Acked-by: Jason Wang <jasowang@...hat.com>

Thanks