Re: [PATCH v2] fat: calculate data area start without overflow

[OGAWA Hirofumi]

hengyul@xxxxxxxxxx writes:

> -	sbi->data_start = sbi->dir_start + rootdir_sectors;
> +	if (check_mul_overflow(sbi->fats, sbi->fat_length,
> +			       &dir_start) ||

Looks like unreadable "\n".

	if (check_mul_overflow(sbi->fats, sbi->fat_length, &dir_start) ||

> +	    check_add_overflow(sbi->fat_start, dir_start, &dir_start) ||
> +	    check_add_overflow(dir_start, rootdir_sectors, &data_start))
> +		goto out_invalid;

Maybe, better to add the error detail?

	    check_add_overflow(dir_start, rootdir_sectors, &data_start)) {
		if (!silent)
			fat_msg(sb, KERN_ERR,
                        	"overflow of root dir or data layout");
		goto out_invalid;
	}

Thanks.

>  	total_sectors = bpb.fat_sectors;
>  	if (total_sectors == 0)
>  		total_sectors = bpb.fat_total_sect;
>  
> -	if (total_sectors < sbi->data_start) {
> +	if (total_sectors < data_start) {
>  		if (!silent)
>  			fat_msg(sb, KERN_ERR,
> -				"data area starts beyond volume (%lu > %u)",
> -				sbi->data_start, total_sectors);
> +				"data area starts beyond volume (%u > %u)",
> +				data_start, total_sectors);
>  		goto out_invalid;
>  	}
>  
> -	total_clusters = (total_sectors - sbi->data_start) / sbi->sec_per_clus;
> +	sbi->dir_start = dir_start;
> +	sbi->data_start = data_start;
> +	total_clusters = (total_sectors - data_start) / sbi->sec_per_clus;
>  
>  	if (!is_fat32(sbi))
>  		sbi->fat_bits = (total_clusters > MAX_FAT12) ? 16 : 12;
>

-- 
OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx>