linux-kernel - Re: [PATCH v2] virtio_ring: Check null pointer

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Date:   Thu, 6 Jan 2022 07:59:24 -0500
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Jiasheng Jiang <jiasheng@...as.ac.cn>
Cc:     jasowang@...hat.com, virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] virtio_ring: Check null pointer

On Tue, Jan 04, 2022 at 11:12:51PM +0800, Jiasheng Jiang wrote:
> As the alloc_indirect_packed() returns kmalloc_array() that could
> allocation fail and return null pointer, it should be check in order to
> prevent the dereference of null pointer.
> 
> Fixes: 1ce9e6055fa0 ("virtio_ring: introduce packed ring support")
> Signed-off-by: Jiasheng Jiang <jiasheng@...as.ac.cn>


Well upstream has:

    virtio_ring: check desc == NULL when using indirect with packed

so this no longer applies.
I think we do need to fix it: the END_USE is missing there.
Sending a patch.


> ---
> v2: Remove the redundant empty line.
> ---
>  drivers/virtio/virtio_ring.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index 71e16b53e9c1..2923d8a68dc3 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -992,6 +992,10 @@ static int virtqueue_add_indirect_packed(struct vring_virtqueue *vq,
>  
>  	head = vq->packed.next_avail_idx;
>  	desc = alloc_indirect_packed(total_sg, gfp);
> +	if (!desc) {
> +		END_USE(vq);
> +		return -ENOMEM;
> +	}
>  
>  	if (unlikely(vq->vq.num_free < 1)) {
>  		pr_debug("Can't add buf len 1 - avail = 0\n");
> -- 
> 2.25.1