From: George Spelvin Date: Mon, 30 Mar 2020 17:38:01 +0000 (+0000) Subject: arm64: kexec_file: Avoid temp buffer for RNG seed X-Git-Tag: v5.15~3602^2~10^6~18 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=99ee28d99607d15c6b88c4a9b9fb4a9f0ebf598c;p=platform%2Fkernel%2Flinux-starfive.git arm64: kexec_file: Avoid temp buffer for RNG seed 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 Acked-by: Will Deacon Cc: Hsin-Yi Wang Cc: Catalin Marinas Cc: linux-arm-kernel@lists.infradead.org Link: https://lore.kernel.org/r/20200330173801.GA9199@SDF.ORG Signed-off-by: Will Deacon --- diff --git a/arch/arm64/kernel/machine_kexec_file.c b/arch/arm64/kernel/machine_kexec_file.c index b40c3b0..e5cbf91 100644 --- a/arch/arm64/kernel/machine_kexec_file.c +++ b/arch/arm64/kernel/machine_kexec_file.c @@ -138,12 +138,12 @@ static int setup_dtb(struct kimage *image, /* 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);