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

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Date:   Wed, 5 Jan 2022 11:20:21 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Jiasheng Jiang <jiasheng@...as.ac.cn>
Cc:     mst <mst@...hat.com>,
        virtualization <virtualization@...ts.linux-foundation.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] virtio_ring: Check null pointer

On Tue, Jan 4, 2022 at 11:13 PM Jiasheng Jiang <jiasheng@...as.ac.cn> 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>
> ---
> 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;

Just notice this:

My tree contains this commit: fc6d70f40b3d0 ("virtio_ring: check desc
== NULL when using indirect with packed"). It has fixed the wrong
error value but not the END_USE().

Thanks

> +       }
>
>         if (unlikely(vq->vq.num_free < 1)) {
>                 pr_debug("Can't add buf len 1 - avail = 0\n");
> --
> 2.25.1
>