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> Cc: Jason A. Donenfeld <Jason@xxxxxxxxx> Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxx> --- 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 e7ea45386c22..974d8a02b966 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> @@ -1673,6 +1674,12 @@ static int mmc_init_card(struct mmc_host *host, u32 ocr, err = mmc_decode_cid(card); if (err) goto free_card; + /* + * Add 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->cid, sizeof(card->cid)); } /* diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c index 68df6b2f49cc..65e0ac031e2a 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> @@ -1443,6 +1444,12 @@ static int mmc_sd_init_card(struct mmc_host *host, u32 ocr, goto free_card; mmc_decode_cid(card); + /* + * Add 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->cid, sizeof(card->cid)); } /* -- 2.35.1
