Re: [Xen-devel] [PATCH linux-next] xen/multicall: xen_mc_callback(): avoid buffer overflow

[David Vrabel <dvrabel@xxxxxxxxxx>]

On 08/02/2013 20:34, Tim Gardner wrote:
> This buffer overflow was introduced with 
> 91e0c5f3dad47838cb2ecc1865ce789a0b7182b1
> (2.6.24).

There's no buffer overflow here. xen_mc_flush() resets b->cbidx.

David

>  arch/x86/xen/multicalls.c |    3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/xen/multicalls.c b/arch/x86/xen/multicalls.c
> index 0d82003..5270407 100644
> --- a/arch/x86/xen/multicalls.c
> +++ b/arch/x86/xen/multicalls.c
> @@ -195,9 +195,10 @@ void xen_mc_callback(void (*fn)(void *), void *data)
>       struct mc_buffer *b = &__get_cpu_var(mc_buffer);
>       struct callback *cb;
>  
> -     if (b->cbidx == MC_BATCH) {
> +     if (b->cbidx >= MC_BATCH) {
>               trace_xen_mc_flush_reason(XEN_MC_FL_CALLBACK);
>               xen_mc_flush();
> +             return;
>       }
>  
>       trace_xen_mc_callback(fn, data);
> 


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