Re: [PATCH 4/6] Under conditions of high load and low resources, it was possible for NDIS (in combination with overlying drivers) to send NET_BUFFER_LIST structures containing NULL MDL's for transmission. This resulted in an immediate bugcheck.

[Paul Durrant <xadimgnik@xxxxxxxxx>]

Coping with NDIS is XENNET's responsibility. Any remedial action should 
be taken there, not here.
  Paul

On 20/07/2021 14:29, Martin Harvey wrote:
> This patch contains the immediate proximate fix for this particular
> issue, instead failing the send with STATUS_INVALID_PARAMETER.
>
> Signed-off-by: Martin Harvey <martin.harvey@xxxxxxxxxx>
> ---
>   src/xenvif/transmitter.c | 9 ++++++++-
>   1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/src/xenvif/transmitter.c b/src/xenvif/transmitter.c
> index 724615d..ea1282c 100644
> --- a/src/xenvif/transmitter.c
> +++ b/src/xenvif/transmitter.c
> @@ -5148,13 +5148,17 @@ TransmitterQueuePacket(
>       PXENVIF_TRANSMITTER_RING        Ring;
>       NTSTATUS                        status;
>   
> +    status = STATUS_INVALID_PARAMETER;
> +    if (Mdl == NULL)
> +        goto fail1;
> +
>       Frontend = Transmitter->Frontend;
>   
>       Packet = __TransmitterGetPacket(Transmitter);
>   
>       status = STATUS_NO_MEMORY;
>       if (Packet == NULL)
> -        goto fail1;
> +        goto fail2;
>   
>       Packet->Mdl = Mdl;
>       Packet->Offset = Offset;
> @@ -5206,6 +5210,9 @@ TransmitterQueuePacket(
>   
>       return STATUS_SUCCESS;
>   
> +fail2:
> +    Error("fail2\n");
> +
>   fail1:
>       Error("fail1 (%08x)\n", status);
>