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mtd: otp: Put factory OTP/NVRAM into the entropy pool 

The factory OTP, if supported, contains factory-programmed
information such as typically the serial number or production
week for the chip.

As this is device-unique information, submit it into the
system entropy pool.

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

Cc: Michael Walle <michael@walle.cc>
Acked-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20230606142931.3721374-1-linus.walleij@linaro.org
This commit is contained in:
Linus Walleij 2023-06-06 16:29:31 +02:00 committed by Miquel Raynal
parent 6db02fdfdc
commit 3b270fac84
1 changed files with 19 additions and 0 deletions
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19
drivers/mtd/mtdcore.c
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@ -23,6 +23,7 @@
#include <linux/idr.h>
#include <linux/backing-dev.h>
#include <linux/gfp.h>
#include <linux/random.h>
#include <linux/slab.h>
#include <linux/reboot.h>
#include <linux/leds.h>
@ -966,6 +967,24 @@ static int mtd_otp_nvmem_add(struct mtd_info *mtd)
}
if (size > 0) {
/*
* The factory OTP contains thing such as a unique serial
* number and is small, so let's read it out and put it
* into the entropy pool.
*/
void *otp;
otp = kmalloc(size, GFP_KERNEL);
if (!otp)
return -ENOMEM;
err = mtd_nvmem_fact_otp_reg_read(mtd, 0, otp, size);
if (err < 0) {
kfree(otp);
return err;
}
add_device_randomness(otp, err);
kfree(otp);
nvmem = mtd_otp_nvmem_register(mtd, "factory-otp", size,
mtd_nvmem_fact_otp_reg_read);
if (IS_ERR(nvmem)) {