Re: [Xen-devel] [PATCH v3 1/2] libxc/xentrace: Replace xc_tbuf_set_cpu_mask with CPU mask with xc_cpumap_t instead of uint32_t

[George Dunlap <george.dunlap@xxxxxxxxxxxxx>]

On 06/20/2014 08:33 PM, Konrad Rzeszutek Wilk wrote:
> @@ -906,6 +949,23 @@ static int parse_evtmask(char *arg)
>       return 0;
>   }
>
> +static int parse_cpumask(const char *arg)
> +{
> +    xc_cpumap_t map;
> +    uint32_t v, i;
> +
> +    map = malloc(sizeof(uint32_t));
> +    if ( !map )
> +        return -ENOMEM;
> +
> +    v = argtol(arg, 0);
> +    for ( i = 0; i < sizeof(uint32_t); i++ )
> +        map[i] = (v >> (i * 8)) & 0xff;
> +
> +    opts.cpu_mask = map;
Sorry for not noticing this befori.  If I'm reading this right, if 
someone sets the cpumask as a hex, then opts.cpu_mask will point to an 
area of memory only 32 bits long.  However, up in set_cpu_mask(), it 
always calls xc_tbuf_set_cpu_mask() with bits equal to xc_get_max_cpus().
On systems with more than 32 logical cpus, won't this cause a buffer 
overrun?  Should you be calling xc_cpumap_alloc() here instead of malloc()?

> @@ -937,7 +997,12 @@ static void parse_args(int argc, char **argv)
>               break;
>
>           case 'c': /* set new cpu mask for filtering*/
> -            opts.cpu_mask = argtol(optarg, 0);
> +            /* Set opts.cpu_mask later as we don't have 'xch' set yet. */
> +            if ( parse_cpumask(optarg) )
Nit: You seem to be parsing it now. :-)

 -George


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