block: Fix potential overflow in blk_report_zones()

For large values of the number of zones reported and/or large zone
sizes, the sector increment calculated with

blk_queue_zone_sectors(q) * n

in blk_report_zones() loop can overflow the unsigned int type used for
the calculation as both "n" and blk_queue_zone_sectors() value are
unsigned int. E.g. for a device with 256 MB zones (524288 sectors),
overflow happens with 8192 or more zones reported.

Changing the return type of blk_queue_zone_sectors() to sector_t, fixes
this problem and avoids overflow problem for all other callers of this
helper too. The same change is also applied to the bdev_zone_sectors()
helper.

Fixes: e76239a3 ("block: add a report_zones method")
Cc: stable@vger.kernel.org
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-zoned.c

@@ -70,7 +70,7 @@ EXPORT_SYMBOL_GPL(__blk_req_zone_write_unlock);
 static inline unsigned int __blkdev_nr_zones(struct request_queue *q,
 					     sector_t nr_sectors)
 {
-	unsigned long zone_sectors = blk_queue_zone_sectors(q);
+	sector_t zone_sectors = blk_queue_zone_sectors(q);
 
 	return (nr_sectors + zone_sectors - 1) >> ilog2(zone_sectors);
 }

include/linux/blkdev.h

@@ -681,7 +681,7 @@ static inline bool blk_queue_is_zoned(struct request_queue *q)
 	}
 }
 
-static inline unsigned int blk_queue_zone_sectors(struct request_queue *q)
+static inline sector_t blk_queue_zone_sectors(struct request_queue *q)
 {
 	return blk_queue_is_zoned(q) ? q->limits.chunk_sectors : 0;
 }
@@ -1418,7 +1418,7 @@ static inline bool bdev_is_zoned(struct block_device *bdev)
 	return false;
 }
 
-static inline unsigned int bdev_zone_sectors(struct block_device *bdev)
+static inline sector_t bdev_zone_sectors(struct block_device *bdev)
 {
 	struct request_queue *q = bdev_get_queue(bdev);