Re: [PATCH 2/2] scsi: sd_zbc: reject disks with too many zones

[Damien Le Moal <dlemoal@kernel.org>]

On 9/11/26 13:11, ZHOU Jiaxiang wrote:
> sd_zbc_read_zones() computes the number of zones with 64-bit
> arithmetic and stores the result in the unsigned int nr_zones field
> of struct zoned_disk_info, silently truncating counts that exceed 32
> bits. The truncated count is later used to size per-zone resources,
> while the device may still report more zones than fit.
> 
> Reject such devices at scan time: more than 4 billion zones is not
> realistic for any medium that exists today, and accepting the
> truncated count produces inconsistent zone bookkeeping.
> 
> Signed-off-by: ZHOU Jiaxiang <26066541r@connect.polyu.hk>
> ---
>  drivers/scsi/sd_zbc.c | 11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/scsi/sd_zbc.c b/drivers/scsi/sd_zbc.c
> index 56e455fb5addd..446628cb3db02 100644
> --- a/drivers/scsi/sd_zbc.c
> +++ b/drivers/scsi/sd_zbc.c
> @@ -589,6 +589,7 @@ int sd_zbc_revalidate_zones(struct scsi_disk *sdkp)
>  int sd_zbc_read_zones(struct scsi_disk *sdkp, struct queue_limits *lim,
>                 u8 buf[SD_BUF_SIZE])
>  {
> +       unsigned long long nr_zones64;
>         unsigned int nr_zones;

Keep the name nr_zones and drop the unsigned int nr_zones variable, it is not
needed.

>         u32 zone_blocks = 0;
>         int ret;
> @@ -620,7 +621,15 @@ int sd_zbc_read_zones(struct scsi_disk *sdkp, struct queue_limits *lim,
>         if (ret != 0)
>                 goto err;
> 
> -       nr_zones = round_up(sdkp->capacity, zone_blocks) >> ilog2(zone_blocks);
> +       nr_zones64 = round_up(sdkp->capacity, zone_blocks) >>
> +                    ilog2(zone_blocks);
> +       if (nr_zones64 > UINT_MAX) {
> +               sd_printk(KERN_ERR, sdkp, "Too many zones (%llu)\n",
> +                         nr_zones64);
> +               ret = -EINVAL;
> +               goto err;
> +       }
> +       nr_zones = nr_zones64;
>         sdkp->early_zone_info.nr_zones = nr_zones;
>         sdkp->early_zone_info.zone_blocks = zone_blocks;
> 
> --
> 2.34.1
> 
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-- 
Damien Le Moal
Western Digital Research