linux-kernel - Re: [PATCH v2] scsi: virtio_scsi: Fix poential NULL pointer dereference in virtscsi_rescan

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Message-ID: <20230213070906-mutt-send-email-mst@kernel.org>
Date:   Mon, 13 Feb 2023 07:09:50 -0500
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Zheng Wang <zyytlz.wz@....com>
Cc:     hackerzheng666@...il.com, jasowang@...hat.com, pbonzini@...hat.com,
        stefanha@...hat.com, jejb@...ux.ibm.com,
        martin.petersen@...cle.com,
        virtualization@...ts.linux-foundation.org,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
        security@...nel.org, alex000young@...il.com
Subject: Re: [PATCH v2] scsi: virtio_scsi: Fix poential NULL pointer
 dereference in  virtscsi_rescan_hotunplug

On Thu, Feb 02, 2023 at 02:41:24PM +0800, Zheng Wang wrote:
> There is no check about the return value of kmalloc in
> virtscsi_rescan_hotunplug. Add the check to avoid use
> of null pointer 'inq_result' in case of the failure
> of kmalloc.
> 
> Signed-off-by: Zheng Wang <zyytlz.wz@....com>
> ---

I fixed a typo in subject and tweaked the patch a bit

> v2:
> - add kfree to avoid memory leak
> ---
>  drivers/scsi/virtio_scsi.c | 13 +++++++++++--
>  1 file changed, 11 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/scsi/virtio_scsi.c b/drivers/scsi/virtio_scsi.c
> index d07d24c06b54..a66d8815d738 100644
> --- a/drivers/scsi/virtio_scsi.c
> +++ b/drivers/scsi/virtio_scsi.c
> @@ -330,7 +330,7 @@ static void virtscsi_handle_param_change(struct virtio_scsi *vscsi,
>  	scsi_device_put(sdev);
>  }
>  
> -static void virtscsi_rescan_hotunplug(struct virtio_scsi *vscsi)
> +static int virtscsi_rescan_hotunplug(struct virtio_scsi *vscsi)
>  {
>  	struct scsi_device *sdev;
>  	struct Scsi_Host *shost = virtio_scsi_host(vscsi->vdev);
> @@ -338,6 +338,11 @@ static void virtscsi_rescan_hotunplug(struct virtio_scsi *vscsi)
>  	int result, inquiry_len, inq_result_len = 256;
>  	char *inq_result = kmalloc(inq_result_len, GFP_KERNEL);
>  
> +	if (!inq_result) {
> +		kfree(inq_result);
> +		return -ENOMEM;
> +	}
> +
>  	shost_for_each_device(sdev, shost) {
>  		inquiry_len = sdev->inquiry_len ? sdev->inquiry_len : 36;
>  
> @@ -366,6 +371,7 @@ static void virtscsi_rescan_hotunplug(struct virtio_scsi *vscsi)
>  	}
>  
>  	kfree(inq_result);
> +	return 0;
>  }
>  
>  static void virtscsi_handle_event(struct work_struct *work)
> @@ -374,12 +380,15 @@ static void virtscsi_handle_event(struct work_struct *work)
>  		container_of(work, struct virtio_scsi_event_node, work);
>  	struct virtio_scsi *vscsi = event_node->vscsi;
>  	struct virtio_scsi_event *event = &event_node->event;
> +	int ret = 0;
>

dropped = 0 here
  
>  	if (event->event &
>  	    cpu_to_virtio32(vscsi->vdev, VIRTIO_SCSI_T_EVENTS_MISSED)) {

and moved declaration here.

>  		event->event &= ~cpu_to_virtio32(vscsi->vdev,
>  						   VIRTIO_SCSI_T_EVENTS_MISSED);
> -		virtscsi_rescan_hotunplug(vscsi);
> +		ret = virtscsi_rescan_hotunplug(vscsi);
> +		if (ret)
> +			return;
>  		scsi_scan_host(virtio_scsi_host(vscsi->vdev));
>  	}
>  
> -- 
> 2.25.1
> 
>