Re: [Qemu-devel] [PATCH] spapr_vty: lookup should only return valid VTY objects

[David Gibson <david@gibson.dropbear.id.au>]

[-- Attachment #1: Type: text/plain, Size: 1703 bytes --]

On Tue, Jun 30, 2015 at 02:04:31PM +0200, Greg Kurz wrote:
> If a guest passes the reg property of a valid VIO object that is not a VTY
> to either H_GET_TERM_CHAR or H_PUT_TERM_CHAR, QEMU hits a dynamic cast
> assertion and aborts.
> 
> PAPR+ says "Hypervisor checks the termno parameter for validity against the
> Vterm IOA unit addresses assigned to the partition, else return H_Parameter."
> 
> This patch adds a type check to ensure vty_lookup() either returns a pointer
> to a valid VTY object or NULL.  H_GET_TERM_CHAR and H_PUT_TERM_CHAR will
> now return H_PARAMETER to the guest instead of crashing.
> 
> The patch has no effect on the reg == 0 hack used to implement the RTAS call
> display-character.
> 
> Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>

Ouch.  That's a nasty bug that's been in there for a long time.

I've applied this to spapr-next.  We should also push to the stable
branch.

> ---
>  hw/char/spapr_vty.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/hw/char/spapr_vty.c b/hw/char/spapr_vty.c
> index 4e464bd15a54..7eeacde31d27 100644
> --- a/hw/char/spapr_vty.c
> +++ b/hw/char/spapr_vty.c
> @@ -228,7 +228,7 @@ VIOsPAPRDevice *vty_lookup(sPAPREnvironment *spapr, target_ulong reg)
>          return spapr_vty_get_default(spapr->vio_bus);
>      }
>  
> -    return sdev;
> +    return object_dynamic_cast(sdev, TYPE_VIO_SPAPR_VTY_DEVICE);
>  }
>  
>  static void spapr_vty_register_types(void)
> 

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

[-- Attachment #2: Type: application/pgp-signature, Size: 819 bytes --]