[dm-devel] [PATCH] dm-zoned: Fix zone report handling

[Shaun Tancheff]

On Thu, Apr 18, 2019 at 4:04 AM Damien Le Moal <damien.lemoal at wdc.com>
wrote:

> The function blkdev_report_zones() returns success even if no zone
> information is reported (empty report). Empty zone reports can only
> happen if the report start sector passed exceeds the device capacity.
> The conditions for this to happen are either a bug in the caller code,
> or, a change in the device that forced the low level driver to change
> the device capacity to a value that is lower than the report start
> sector. This situation includes a failed disk revalidation resulting in
> the disk capacity being changed to 0.
>
> If this change happens while dm-zoned is in its initialization phase
> executing dmz_init_zones(), this function may enter an infinite loop
> and hang the system. To avoid this, add a check to disallow empty zone
> reports and bail out early. Also fix the function dmz_update_zone() to
> make sure that the report for the requested zone was correctly obtained.
>
> Fixes: 3b1a94c88b79 ("dm zoned: drive-managed zoned block device target")
> Cc: stable at vger.kernel.org
> Signed-off-by: Damien Le Moal <damien.lemoal at wdc.com>
> ---
>  drivers/md/dm-zoned-metadata.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/drivers/md/dm-zoned-metadata.c
> b/drivers/md/dm-zoned-metadata.c
> index fa68336560c3..d8334cd45d7c 100644
> --- a/drivers/md/dm-zoned-metadata.c
> +++ b/drivers/md/dm-zoned-metadata.c
> @@ -1169,6 +1169,9 @@ static int dmz_init_zones(struct dmz_metadata *zmd)
>                         goto out;
>                 }
>
> +               if (!nr_blkz)
> +                       break;
> +
>                 /* Process report */
>                 for (i = 0; i < nr_blkz; i++) {
>                         ret = dmz_init_zone(zmd, zone, &blkz[i]);
> @@ -1204,6 +1207,8 @@ static int dmz_update_zone(struct dmz_metadata *zmd,
> struct dm_zone *zone)
>         /* Get zone information from disk */
>         ret = blkdev_report_zones(zmd->dev->bdev, dmz_start_sect(zmd,
> zone),
>                                   &blkz, &nr_blkz, GFP_NOIO);
> +       if (!nr_blkz)
> +               ret = -EIO;
>         if (ret) {
>                 dmz_dev_err(zmd->dev, "Get zone %u report failed",
>                             dmz_id(zmd, zone));
>

Reviewed-by: Shaun Tancheff <shaun at tancheff.com>


> --
> 2.20.1
>
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