linux-kernel - [PATCH AUTOSEL 5.18 124/159] init: call time_init() before rand

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Message-Id: <20220530132425.1929512-124-sashal@kernel.org>
Date:   Mon, 30 May 2022 09:23:49 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     "Jason A. Donenfeld" <Jason@...c4.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Stafford Horne <shorne@...il.com>,
        Sasha Levin <sashal@...nel.org>, rostedt@...dmis.org,
        mhiramat@...nel.org, vbabka@...e.cz, ahalaney@...hat.com,
        mark-pk.tsai@...iatek.com, peterz@...radead.org
Subject: [PATCH AUTOSEL 5.18 124/159] init: call time_init() before rand_initialize()

From: "Jason A. Donenfeld" <Jason@...c4.com>

[ Upstream commit fe222a6ca2d53c38433cba5d3be62a39099e708e ]

Currently time_init() is called after rand_initialize(), but
rand_initialize() makes use of the timer on various platforms, and
sometimes this timer needs to be initialized by time_init() first. In
order for random_get_entropy() to not return zero during early boot when
it's potentially used as an entropy source, reverse the order of these
two calls. The block doing random initialization was right before
time_init() before, so changing the order shouldn't have any complicated
effects.

Cc: Andrew Morton <akpm@...ux-foundation.org>
Reviewed-by: Stafford Horne <shorne@...il.com>
Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 init/main.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/init/main.c b/init/main.c
index 98182c3c2c4b..92783732a36f 100644
--- a/init/main.c
+++ b/init/main.c
@@ -1035,11 +1035,13 @@ asmlinkage __visible void __init __no_sanitize_address start_kernel(void)
 	softirq_init();
 	timekeeping_init();
 	kfence_init();
+	time_init();
 
 	/*
 	 * For best initial stack canary entropy, prepare it after:
 	 * - setup_arch() for any UEFI RNG entropy and boot cmdline access
 	 * - timekeeping_init() for ktime entropy used in rand_initialize()
+	 * - time_init() for making random_get_entropy() work on some platforms
 	 * - rand_initialize() to get any arch-specific entropy like RDRAND
 	 * - add_latent_entropy() to get any latent entropy
 	 * - adding command line entropy
@@ -1049,7 +1051,6 @@ asmlinkage __visible void __init __no_sanitize_address start_kernel(void)
 	add_device_randomness(command_line, strlen(command_line));
 	boot_init_stack_canary();
 
-	time_init();
 	perf_event_init();
 	profile_init();
 	call_function_init();
-- 
2.35.1