RE: [PATCH] Add check for empty List in FdoCsqPeekNextIrp.

[Paul Durrant <xadimgnik@xxxxxxxxx>]

> -----Original Message-----
> From: Troy Crosley <troycrosley@xxxxxxxxx>
> Sent: 19 October 2020 19:57
> To: win-pv-devel@xxxxxxxxxxxxxxxxxxxx
> Cc: paul@xxxxxxx; ben.chalmers@xxxxxxxxxx; owen.smith@xxxxxxxxxx; Troy 
> Crosley <troycrosley@xxxxxxxxx>
> Subject: [PATCH] Add check for empty List in FdoCsqPeekNextIrp.
> 
> Under certain situations, such as when input is being sent during driver
> install or sleep transition, FdoCsqPeekNextIrp can be called with an
> empty Fdo->List. In that case, FdoCsqPeekNextIrp dereferences the list
> head and returns an invalid IRP; it should check for this error
> condition.
> 
> Signed-off-by: Troy Crosley <troycrosley@xxxxxxxxx>

Acked-by: Paul Durrant <paul@xxxxxxx>

> ---
>  src/xenhid/fdo.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/src/xenhid/fdo.c b/src/xenhid/fdo.c
> index c2ef7c8..04d3d7f 100644
> --- a/src/xenhid/fdo.c
> +++ b/src/xenhid/fdo.c
> @@ -123,8 +123,12 @@ FdoCsqPeekNextIrp(
>      else
>          ListEntry = Irp->Tail.Overlay.ListEntry.Flink;
> 
> -    NextIrp = CONTAINING_RECORD(ListEntry, IRP, Tail.Overlay.ListEntry);
>      // should walk through the list until a match against Context is found
> +    if (ListEntry != &Fdo->List)
> +        NextIrp = CONTAINING_RECORD(ListEntry, IRP, Tail.Overlay.ListEntry);
> +    else
> +        NextIrp = NULL;
> +
>      return NextIrp;
>  }
> 
> --
> 2.20.1