null_blk: fix validation of block size

Block size should be between 512 and PAGE_SIZE and be a power of 2. The current
check does not validate this, so update the check.

Without this patch, null_blk would Oops due to a null pointer deref when
loaded with bs=1536 [1].

Link: https://lore.kernel.org/all/[email protected]/

Signed-off-by: Andreas Hindborg <[email protected]>
Reviewed-by: Ming Lei <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
[axboe: remove unnecessary braces and != 0 check]
Signed-off-by: Jens Axboe <[email protected]>

Author: metaspace

drivers/block/null_blk/main.c

@@ -1824,8 +1824,8 @@ static int null_validate_conf(struct nullb_device *dev)
 		dev->queue_mode = NULL_Q_MQ;
 	}
 
-	dev->blocksize = round_down(dev->blocksize, 512);
-	dev->blocksize = clamp_t(unsigned int, dev->blocksize, 512, 4096);
+	if (blk_validate_block_size(dev->blocksize))
+		return -EINVAL;
 
 	if (dev->use_per_node_hctx) {
 		if (dev->submit_queues != nr_online_nodes)