linux-kernel - [PATCH] random: Use arch_get_random*_early() in random

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Date:   Fri, 28 Oct 2022 17:00:42 +0100
From:   Jean-Philippe Brucker <jean-philippe@...aro.org>
To:     Jason@...c4.com, tytso@....edu
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        ardb@...nel.org, andre.przywara@....com,
        Jean-Philippe Brucker <jean-philippe@...aro.org>
Subject: [PATCH] random: Use arch_get_random*_early() in random_init()

While reworking the archrandom handling, commit d349ab99eec7 ("random:
handle archrandom with multiple longs") switched to the non-early
archrandom helpers in random_init(), which broke initialization of the
entropy pool from the arm64 random generator.

Indeed at that point the arm64 CPU features, which verify that all CPUs
have compatible capabilities, are not finalized so arch_get_random_seed_longs()
is unsuccessful. Instead random_init() should use the _early functions,
which check only the boot CPU on arm64. On other architectures the
_early functions directly call the normal ones.

Fixes: d349ab99eec7 ("random: handle archrandom with multiple longs")
Signed-off-by: Jean-Philippe Brucker <jean-philippe@...aro.org>
---
 drivers/char/random.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/char/random.c b/drivers/char/random.c
index 2fe28eeb2f38..085af17c32f5 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -791,13 +791,14 @@ void __init random_init_early(const char *command_line)
 #endif
 
 	for (i = 0, arch_bits = sizeof(entropy) * 8; i < ARRAY_SIZE(entropy);) {
-		longs = arch_get_random_seed_longs(entropy, ARRAY_SIZE(entropy) - i);
+		longs = arch_get_random_seed_longs_early(entropy,
+							 ARRAY_SIZE(entropy) - i);
 		if (longs) {
 			_mix_pool_bytes(entropy, sizeof(*entropy) * longs);
 			i += longs;
 			continue;
 		}
-		longs = arch_get_random_longs(entropy, ARRAY_SIZE(entropy) - i);
+		longs = arch_get_random_longs_early(entropy, ARRAY_SIZE(entropy) - i);
 		if (longs) {
 			_mix_pool_bytes(entropy, sizeof(*entropy) * longs);
 			i += longs;
-- 
2.37.3