null_blk: Fail zone append to conventional zones

BugLink: https://bugs.launchpad.net/bugs/1910111

commit 2e896d8 upstream.

Conventional zones do not have a write pointer and so cannot accept zone
append writes. Make sure to fail any zone append write command issued to
a conventional zone.

Reported-by: Naohiro Aota <naohiro.aota@wdc.com>
Fixes: e0489ed ("null_blk: Support REQ_OP_ZONE_APPEND")
Cc: stable@vger.kernel.org
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>

drivers/block/null_blk_zoned.c

@@ -339,8 +339,11 @@ static blk_status_t null_zone_write(struct nullb_cmd *cmd, sector_t sector,
 
 	trace_nullb_zone_op(cmd, zno, zone->cond);
 
-	if (zone->type == BLK_ZONE_TYPE_CONVENTIONAL)
+	if (zone->type == BLK_ZONE_TYPE_CONVENTIONAL) {
+		if (append)
+			return BLK_STS_IOERR;
 		return null_process_cmd(cmd, REQ_OP_WRITE, sector, nr_sectors);
+	}
 
 	null_lock_zone(dev, zno);