From b277da0a8a594308e17881f4926879bd5fca2a2d Mon Sep 17 00:00:00 2001 From: Mike Snitzer Date: Sat, 4 Oct 2014 10:55:32 -0600 Subject: block: disable entropy contributions for nonrot devices Clear QUEUE_FLAG_ADD_RANDOM in all block drivers that set QUEUE_FLAG_NONROT. Historically, all block devices have automatically made entropy contributions. But as previously stated in commit e2e1a148 ("block: add sysfs knob for turning off disk entropy contributions"): - On SSD disks, the completion times aren't as random as they are for rotational drives. So it's questionable whether they should contribute to the random pool in the first place. - Calling add_disk_randomness() has a lot of overhead. There are more reliable sources for randomness than non-rotational block devices. From a security perspective it is better to err on the side of caution than to allow entropy contributions from unreliable "random" sources. Signed-off-by: Mike Snitzer Signed-off-by: Jens Axboe --- drivers/block/nbd.c | 1 + 1 file changed, 1 insertion(+) (limited to 'drivers/block/nbd.c') diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index fb31b8ee4372..4bc2a5cb9935 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -847,6 +847,7 @@ static int __init nbd_init(void) * Tell the block layer that we are not a rotational device */ queue_flag_set_unlocked(QUEUE_FLAG_NONROT, disk->queue); + queue_flag_clear_unlocked(QUEUE_FLAG_ADD_RANDOM, disk->queue); disk->queue->limits.discard_granularity = 512; disk->queue->limits.max_discard_sectors = UINT_MAX; disk->queue->limits.discard_zeroes_data = 0; -- cgit v1.2.3