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 <snitzer@redhat.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/drivers/block/mtip32xx/mtip32xx.c b/drivers/block/mtip32xx/mtip32xx.c
index db1e956..936f8c1 100644
--- a/drivers/block/mtip32xx/mtip32xx.c
+++ b/drivers/block/mtip32xx/mtip32xx.c
@@ -3952,6 +3952,7 @@
/* Set device limits. */
set_bit(QUEUE_FLAG_NONROT, &dd->queue->queue_flags);
+ clear_bit(QUEUE_FLAG_ADD_RANDOM, &dd->queue->queue_flags);
blk_queue_max_segments(dd->queue, MTIP_MAX_SG);
blk_queue_physical_block_size(dd->queue, 4096);
blk_queue_max_hw_sectors(dd->queue, 0xffff);