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From:   Nicolai Stange <nstange@suse.de>
To:     "Theodore Y. Ts'o" <tytso@mit.edu>
Cc:     linux-crypto@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
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        Eric Biggers <ebiggers@kernel.org>,
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        =?UTF-8?q?Stephan=20M=C3=BCller?= <smueller@chronox.de>,
        Torsten Duwe <duwe@suse.de>, Petr Tesarik <ptesarik@suse.cz>,
        Nicolai Stange <nstange@suse.de>
Subject: [RFC PATCH 24/41] init: call time_init() before rand_initialize()
Date:   Mon, 21 Sep 2020 09:58:40 +0200
Message-Id: <20200921075857.4424-25-nstange@suse.de>
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Commit d55535232c3d ("random: move rand_initialize() earlier") moved the
rand_initialize() invocation from the early initcalls to right after
timekeeping_init(), but before time_init().

However, rand_initialize() would indirectly invoke random_get_entropy(),
which is an alias to get_cycles() on most archs, in case an architectural
RNG is not available. Problem is that on some archs, e.g. ARM,
get_cycles() can only be relied upon when time_init() has completed.

Move the invocation of time_init() a couple of lines up in start_kernel()
so that it gets called before rand_initialize().

Note that random_get_entropy() data doesn't get any entropy credit and
thus, this issue is not to be considered a bug, but more of an
inconsistency.

Fixes: d55535232c3d ("random: move rand_initialize() earlier")
Signed-off-by: Nicolai Stange <nstange@suse.de>
---
 init/main.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/init/main.c b/init/main.c
index ae78fb68d231..30892675f48e 100644
--- a/init/main.c
+++ b/init/main.c
@@ -942,6 +942,7 @@ asmlinkage __visible void __init __no_sanitize_address start_kernel(void)
 	hrtimers_init();
 	softirq_init();
 	timekeeping_init();
+	time_init();
 
 	/*
 	 * For best initial stack canary entropy, prepare it after:
@@ -956,7 +957,6 @@ 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();
-- 
2.26.2