Re: [PATCH v2] perf: prevent overflow in size calculation

[Cody P Schafer <cody@linux.vnet.ibm.com>]

>   	struct annotation *notes = symbol__annotation(sym);
>   	const size_t size = symbol__size(sym);
> -	size_t sizeof_sym_hist = (sizeof(struct sym_hist) + size * sizeof(u64));
> +	size_t sizeof_sym_hist;
> +
> +	/* Check for overflow when calculating sizeof_sym_hist */
> +	if (size > (SIZE_MAX / sizeof(u64) - sizeof(struct sym_hist)))
> +		return -1;
> +
> +	sizeof_sym_hist = (sizeof(struct sym_hist) + size * sizeof(u64));
> +
> +	/* Check for overflow in zalloc argument */
> +	if (sizeof_sym_hist > (SIZE_MAX / symbol_conf.nr_events
> +				- sizeof(*notes->src)))
> +		return -1;
>
>   	notes->src = zalloc(sizeof(*notes->src) + symbol_conf.nr_events * sizeof_sym_hist);
>   	if (notes->src == NULL)
>

Actually, I don't think this is correct either (subtraction seems to 
occur in the wrong spot).