On Mon, 25 Apr 2022 at 22:56, Linus Walleij <linus.walleij@xxxxxxxxxx> wrote:
>
> 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@xxxxxxx>
> Acked-by: Jason A. Donenfeld <Jason@xxxxxxxxx>
> Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
Applied for next, thanks!
Kind regards
Uffe
> ---
> ChangeLog v1->v2:
> - Move the device_add_randomness() into each mmc_decode_cid()
> function for MMC and SD card.
> - Use the raw cid, no reason to unpack the data before using
> it for this purpose.
> ---
> drivers/mmc/core/mmc.c | 7 +++++++
> drivers/mmc/core/sd.c | 7 +++++++
> 2 files changed, 14 insertions(+)
>
> diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
> index 6b78ae45c4c9..9804a06ffadd 100644
> --- a/drivers/mmc/core/mmc.c
> +++ b/drivers/mmc/core/mmc.c
> @@ -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.
> diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c
> index 68df6b2f49cc..c5f1df6ce4c0 100644
> --- a/drivers/mmc/core/sd.c
> +++ b/drivers/mmc/core/sd.c
> @@ -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.
> --
> 2.35.1
>
