From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id AE794C433EF for ; Wed, 29 Dec 2021 21:13:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231372AbhL2VNu (ORCPT ); Wed, 29 Dec 2021 16:13:50 -0500 Received: from isilmar-4.linta.de ([136.243.71.142]:33264 "EHLO isilmar-4.linta.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230488AbhL2VNt (ORCPT ); Wed, 29 Dec 2021 16:13:49 -0500 X-isilmar-external: YES X-isilmar-external: YES X-isilmar-external: YES X-isilmar-external: YES X-isilmar-external: YES X-isilmar-external: YES X-isilmar-external: YES Received: from owl.dominikbrodowski.net (owl.brodo.linta [10.2.0.111]) by isilmar-4.linta.de (Postfix) with ESMTPSA id 22BD6201306; Wed, 29 Dec 2021 21:13:48 +0000 (UTC) Received: by owl.dominikbrodowski.net (Postfix, from userid 1000) id D0BF580F4B; Wed, 29 Dec 2021 22:10:17 +0100 (CET) From: Dominik Brodowski To: "Jason A . Donenfeld" Cc: linux-kernel@vger.kernel.org, Theodore Ts'o , "Ivan T . Ivanov" , Ard Biesheuvel , linux-efi@vger.kernel.org, linux@dominikbrodowski.net Subject: [PATCH v8 3/7] random: do not throw away excess input to crng_fast_load Date: Wed, 29 Dec 2021 22:10:05 +0100 Message-Id: <20211229211009.108091-3-linux@dominikbrodowski.net> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20211229211009.108091-1-linux@dominikbrodowski.net> References: <20211228153826.448805-1-Jason@zx2c4.com> <20211229211009.108091-1-linux@dominikbrodowski.net> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-efi@vger.kernel.org From: "Jason A. Donenfeld" When crng_fast_load() is called by add_hwgenerator_randomness(), we currently will advance to crng_init==1 once we've acquired 64 bytes, and then throw away the rest of the buffer. Usually, that is not a problem: When add_hwgenerator_randomness() gets called via EFI or DT during setup_arch(), there won't be any IRQ randomness. Therefore, the 64 bytes passed by EFI exactly matches what is needed to advance to crng_init==1. Usually, DT seems to pass 64 bytes as well -- with one notable exception being kexec, which hands over 128 bytes of entropy to the kexec'd kernel. In that case, we'll advance to crng_init==1 once 64 of those bytes are consumed by crng_fast_load(), but won't continue onward feeding in bytes to progress to crng_init==2. This commit fixes the issue by feeding any leftover bytes into the next phase in add_hwgenerator_randomness(). Signed-off-by: Jason A. Donenfeld [linux@dominikbrodowski.net: rewrite commit message] Signed-off-by: Dominik Brodowski --- drivers/char/random.c | 19 ++++++++++++------- 1 file changed, 12 insertions(+), 7 deletions(-) diff --git a/drivers/char/random.c b/drivers/char/random.c index 916cf791ed0e..21166188b7e1 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -919,12 +919,14 @@ static struct crng_state *select_crng(void) /* * crng_fast_load() can be called by code in the interrupt service - * path. So we can't afford to dilly-dally. + * path. So we can't afford to dilly-dally. Returns the number of + * bytes processed from cp. */ -static int crng_fast_load(const char *cp, size_t len) +static size_t crng_fast_load(const char *cp, size_t len) { unsigned long flags; char *p; + size_t ret = 0; if (!spin_trylock_irqsave(&primary_crng.lock, flags)) return 0; @@ -935,7 +937,7 @@ static int crng_fast_load(const char *cp, size_t len) p = (unsigned char *) &primary_crng.state[4]; while (len > 0 && crng_init_cnt < CRNG_INIT_CNT_THRESH) { p[crng_init_cnt % CHACHA_KEY_SIZE] ^= *cp; - cp++; crng_init_cnt++; len--; + cp++; crng_init_cnt++; len--; ret++; } spin_unlock_irqrestore(&primary_crng.lock, flags); if (crng_init_cnt >= CRNG_INIT_CNT_THRESH) { @@ -943,7 +945,7 @@ static int crng_fast_load(const char *cp, size_t len) crng_init = 1; pr_notice("fast init done\n"); } - return 1; + return ret; } /* @@ -1294,7 +1296,7 @@ void add_interrupt_randomness(int irq) if (unlikely(crng_init == 0)) { if ((fast_pool->count >= 64) && crng_fast_load((char *) fast_pool->pool, - sizeof(fast_pool->pool))) { + sizeof(fast_pool->pool)) > 0) { fast_pool->count = 0; fast_pool->last = now; } @@ -2295,8 +2297,11 @@ void add_hwgenerator_randomness(const char *buffer, size_t count, struct entropy_store *poolp = &input_pool; if (unlikely(crng_init == 0)) { - crng_fast_load(buffer, count); - return; + size_t ret = crng_fast_load(buffer, count); + count -= ret; + buffer += ret; + if (!count || crng_init == 0) + return; } /* Suspend writing if we're above the trickle threshold. -- 2.34.1