After using get_random_bytes(), you want to wipe the buffer
afterward so the seed remains secret.
In this case, we can eliminate the temporary buffer entirely.
fdt_setprop_placeholder() returns a pointer to the property value
buffer, allowing us to put the random data directly in there without
using a temporary buffer at all. Faster and less stack all in one.
Signed-off-by: George Spelvin <lkml@sdf.org>
Acked-by: Will Deacon <will@kernel.org>
Cc: Hsin-Yi Wang <hsinyi@chromium.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Link: https://lore.kernel.org/r/20200330173801.GA9199@SDF.ORG
Signed-off-by: Will Deacon <will@kernel.org>
/* add rng-seed */
if (rng_is_initialized()) {
- u8 rng_seed[RNG_SEED_SIZE];
- get_random_bytes(rng_seed, RNG_SEED_SIZE);
- ret = fdt_setprop(dtb, off, FDT_PROP_RNG_SEED, rng_seed,
- RNG_SEED_SIZE);
+ void *rng_seed;
+ ret = fdt_setprop_placeholder(dtb, off, FDT_PROP_RNG_SEED,
+ RNG_SEED_SIZE, &rng_seed);
if (ret)
goto out;
+ get_random_bytes(rng_seed, RNG_SEED_SIZE);
} else {
pr_notice("RNG is not initialised: omitting \"%s\" property\n",
FDT_PROP_RNG_SEED);