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/ide/ide-disk.c b/drivers/ide/ide-disk.c
index ee88038..56b9708 100644
--- a/drivers/ide/ide-disk.c
+++ b/drivers/ide/ide-disk.c
@@ -685,8 +685,10 @@
printk(KERN_INFO "%s: max request size: %dKiB\n", drive->name,
queue_max_sectors(q) / 2);
- if (ata_id_is_ssd(id))
+ if (ata_id_is_ssd(id)) {
queue_flag_set_unlocked(QUEUE_FLAG_NONROT, q);
+ queue_flag_clear_unlocked(QUEUE_FLAG_ADD_RANDOM, q);
+ }
/* calculate drive capacity, and select LBA if possible */
ide_disk_get_capacity(drive);