Re: [PATCH nvmet-v1 1/1] nvmet: zns: reject full zone report when buffer is too small

[Christoph Hellwig <hch@lst.de>]

On Thu, Jul 09, 2026 at 02:51:39PM +0800, Xixin Liu wrote:
> Zone Management Receive uses the Partial Report (PR) bit in dword 13.  On a
> partial report (PR bit set), the host accepts an incomplete listing and
> Number of Zones must not exceed the zone descriptors copied to the host
> buffer.  On a full report (PR bit clear), Number of Zones is the total
> number of matching zones and every descriptor must fit in the buffer (ZNS
> Command Set Specification Rev 1.2, section 3.4.2).
> 
> nvmet_bdev_zone_zmgmt_recv_work() already caps Number of Zones for partial
> reports, but on a full report it may still succeed when the buffer only
> holds part of the matching descriptors.  Reject the command in that case.
> 
> Signed-off-by: Xixin Liu <liuxixin@kylinos.cn>
> ---
>  drivers/nvme/target/zns.c | 15 ++++++++++++---
>  1 file changed, 12 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/nvme/target/zns.c b/drivers/nvme/target/zns.c
> index f00921931eb6..a53986fcc04a 100644
> --- a/drivers/nvme/target/zns.c
> +++ b/drivers/nvme/target/zns.c
> @@ -295,11 +295,20 @@ static void nvmet_bdev_zone_zmgmt_recv_work(struct work_struct *w)
>  	}
>  
>  	/*
> -	 * When partial bit is set nr_zones must indicate the number of zone
> -	 * descriptors actually transferred.
> +	 * Partial report (PR bit set): the host accepts an incomplete listing,
> +	 * so cap Number of Zones to the descriptors that fit in the buffer.
> +	 * Full report (PR bit clear): Number of Zones is the match count; fail
> +	 * if the buffer cannot hold every matching zone descriptor.
>  	 */
> -	if (req->cmd->zmr.pr)
> +	if (req->cmd->zmr.pr) {
>  		rz_data.nr_zones = min(rz_data.nr_zones, rz_data.out_nr_zones);
> +	} else {
> +		if (rz_data.nr_zones > rz_data.out_nr_zones) {
> +			req->error_loc = offsetof(struct nvme_zone_mgmt_recv_cmd, numd);

Overly line here.  Easily fixed by using and else if above.