Re: [Qemu-devel] [PATCH] spapr: fix write-past-end-of-array error in cpu core device init code

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

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On Mon, Jun 27, 2016 at 06:28:15PM +0200, Greg Kurz wrote:
> This fixes a potential QEMU crash introduced by commit 3b542549661.
> 
> Signed-off-by: Greg Kurz <groug@kaod.org>
> ---
>  hw/ppc/spapr_cpu_core.c |    3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)

Ugh.  The existing code is wrong in the case where the failure happens
after the loop.

But this version is wrong in the case it happens during the loop - it
will fail to clean up the last object created.

> diff --git a/hw/ppc/spapr_cpu_core.c b/hw/ppc/spapr_cpu_core.c
> index 3a5da09b9902..8b802a6fcf0b 100644
> --- a/hw/ppc/spapr_cpu_core.c
> +++ b/hw/ppc/spapr_cpu_core.c
> @@ -309,10 +309,9 @@ static void spapr_cpu_core_realize(DeviceState *dev, Error **errp)
>      }
>  
>  err:
> -    while (i >= 0) {
> +    while (--i >= 0) {
>          obj = sc->threads + i * size;
>          object_unparent(obj);
> -        i--;
>      }
>      g_free(sc->threads);
>      error_propagate(errp, local_err);
> 

-- 
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

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