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From:   Jason Wang <jasowang@redhat.com>
To:     mst@redhat.com, jasowang@redhat.com
Cc:     virtualization@lists.linux-foundation.org,
        linux-kernel@vger.kernel.org, f.hetzelt@tu-berlin.de,
        david.kaplan@amd.com, konrad.wilk@oracle.com,
        Paolo Bonzini <pbonzini@redhat.com>,
        Stefan Hajnoczi <stefanha@redhat.com>
Subject: [PATCH 1/9] virtio-blk: validate num_queues during probe
Date:   Mon, 13 Sep 2021 13:53:45 +0800
Message-Id: <20210913055353.35219-2-jasowang@redhat.com>
In-Reply-To: <20210913055353.35219-1-jasowang@redhat.com>
References: <20210913055353.35219-1-jasowang@redhat.com>
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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 */
+	if (err || !num_vqs)
 		num_vqs = 1;
 
 	num_vqs = min_t(unsigned int, nr_cpu_ids, num_vqs);
-- 
2.25.1