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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        Dominik Brodowski <linux@dominikbrodowski.net>,
        "Jason A. Donenfeld" <Jason@zx2c4.com>
Subject: [PATCH 4.19 052/234] random: do not re-init if crng_reseed completes before primary init
Date:   Thu, 23 Jun 2022 18:41:59 +0200
Message-Id: <20220623164344.538866268@linuxfoundation.org>
In-Reply-To: <20220623164343.042598055@linuxfoundation.org>
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From: "Jason A. Donenfeld" <Jason@zx2c4.com>

commit 9c3ddde3f811aabbb83778a2a615bf141b4909ef upstream.

If the bootloader supplies sufficient material and crng_reseed() is called
very early on, but not too early that wqs aren't available yet, then we
might transition to crng_init==2 before rand_initialize()'s call to
crng_initialize_primary() made. Then, when crng_initialize_primary() is
called, if we're trusting the CPU's RDRAND instructions, we'll
needlessly reinitialize the RNG and emit a message about it. This is
mostly harmless, as numa_crng_init() will allocate and then free what it
just allocated, and excessive calls to invalidate_batched_entropy()
aren't so harmful. But it is funky and the extra message is confusing,
so avoid the re-initialization all together by checking for crng_init <
2 in crng_initialize_primary(), just as we already do in crng_reseed().

Reviewed-by: Dominik Brodowski <linux@dominikbrodowski.net>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/char/random.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -829,7 +829,7 @@ static void __init crng_initialize_prima
 {
 	memcpy(&crng->state[0], "expand 32-byte k", 16);
 	_extract_entropy(&input_pool, &crng->state[4], sizeof(__u32) * 12, 0);
-	if (crng_init_try_arch_early(crng) && trust_cpu) {
+	if (crng_init_try_arch_early(crng) && trust_cpu && crng_init < 2) {
 		invalidate_batched_entropy();
 		numa_crng_init();
 		crng_init = 2;