Commit ac9d2555 authored by Linus Walleij's avatar Linus Walleij Committed by Ulf Hansson
Browse files

mmc: core: Add CIDs for cards to the entropy pool 



To make the entropy pool a bit better we can toss in the
CID for eMMC and SD cards into it, usually the serial
number portion is at least unique.

This does not count as improvement of the entropy but
in practice it makes it a bit more random to mix in these
numbers.

Cc: Theodore Ts'o <tytso@mit.edu>
Acked-by: default avatarJason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: default avatarLinus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20220425205442.1347837-1-linus.walleij@linaro.org


Signed-off-by: default avatarUlf Hansson <ulf.hansson@linaro.org>
parent 23e09be2

drivers/mmc/core/mmc.c

+7 −0
Original line number Diff line number Diff line
@@ -12,6 +12,7 @@ 
#include <linux/slab.h>

#include <linux/stat.h>

#include <linux/pm_runtime.h>

#include <linux/random.h>

#include <linux/sysfs.h>



#include <linux/mmc/host.h>
@@ -71,6 +72,12 @@ static int mmc_decode_cid(struct mmc_card *card) 
{

	u32 *resp = card->raw_cid;



	/*

	 * Add the raw card ID (cid) data to the entropy pool. It doesn't

	 * matter that not all of it is unique, it's just bonus entropy.

	 */

	add_device_randomness(&card->raw_cid, sizeof(card->raw_cid));



	/*

	 * The selection of the format here is based upon published

	 * specs from sandisk and from what people have reported.

drivers/mmc/core/sd.c

+7 −0
Original line number Diff line number Diff line
@@ -12,6 +12,7 @@ 
#include <linux/slab.h>

#include <linux/stat.h>

#include <linux/pm_runtime.h>

#include <linux/random.h>

#include <linux/scatterlist.h>

#include <linux/sysfs.h>
@@ -83,6 +84,12 @@ void mmc_decode_cid(struct mmc_card *card) 
{

	u32 *resp = card->raw_cid;



	/*

	 * Add the raw card ID (cid) data to the entropy pool. It doesn't

	 * matter that not all of it is unique, it's just bonus entropy.

	 */

	add_device_randomness(&card->raw_cid, sizeof(card->raw_cid));



	/*

	 * SD doesn't currently have a version field so we will

	 * have to assume we can parse this.