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Date:   Mon, 13 Sep 2021 09:48:14 +0200
From:   Stefano Garzarella <sgarzare@redhat.com>
To:     Jason Wang <jasowang@redhat.com>
Cc:     mst@redhat.com, david.kaplan@amd.com, konrad.wilk@oracle.com,
        f.hetzelt@tu-berlin.de, linux-kernel@vger.kernel.org,
        virtualization@lists.linux-foundation.org,
        Stefan Hajnoczi <stefanha@redhat.com>,
        Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: [PATCH 1/9] virtio-blk: validate num_queues during probe
Message-ID: <20210913074814.wcrrisaomlhvtmo5@steredhat>
References: <20210913055353.35219-1-jasowang@redhat.com>
 <20210913055353.35219-2-jasowang@redhat.com>
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On Mon, Sep 13, 2021 at 01:53:45PM +0800, Jason Wang wrote:
>If an untrusted device neogitates BLK_F_MQ but advertises a zero
>num_queues, the driver may end up trying to allocating zero size
>buffers where ZERO_SIZE_PTR is returned which may pass the checking
>against the NULL. This will lead unexpected results.
>
>Fixing this by using single queue if num_queues is zero.
>
>Cc: Paolo Bonzini <pbonzini@redhat.com>
>Cc: Stefan Hajnoczi <stefanha@redhat.com>
>Signed-off-by: Jason Wang <jasowang@redhat.com>
>---
> drivers/block/virtio_blk.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
>diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
>index e574fbf5e6df..f130d12df4b9 100644
>--- a/drivers/block/virtio_blk.c
>+++ b/drivers/block/virtio_blk.c
>@@ -498,7 +498,8 @@ static int init_vq(struct virtio_blk *vblk)
> 	err = virtio_cread_feature(vdev, VIRTIO_BLK_F_MQ,
> 				   struct virtio_blk_config, num_queues,
> 				   &num_vqs);
>-	if (err)
>+	/* We need at least on virtqueue */

s/on/one/

The rest LGTM.

Stefano

>+	if (err || !num_vqs)
> 		num_vqs = 1;
>
> 	num_vqs = min_t(unsigned int, nr_cpu_ids, num_vqs);
>-- 
>2.25.1
>
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