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 DC2C4C4332F for ; Sun, 18 Dec 2022 18:31:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231267AbiLRSba (ORCPT ); Sun, 18 Dec 2022 13:31:30 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35374 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230493AbiLRSag (ORCPT ); Sun, 18 Dec 2022 13:30:36 -0500 Received: from mail-wr1-x42b.google.com (mail-wr1-x42b.google.com [IPv6:2a00:1450:4864:20::42b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A239D1CD for ; Sun, 18 Dec 2022 10:19:12 -0800 (PST) Received: by mail-wr1-x42b.google.com with SMTP id co23so6813844wrb.4 for ; Sun, 18 Dec 2022 10:19:12 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mail.huji.ac.il; s=mailhuji; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=/hihxsb5erPMsln/gUSY59M8NixzubgoudYMNGqOBjo=; b=NGfdREvNprmAmUc2BJDXguEpC2w1uGkTEXFyrIXXxIuEwHTPjUk4hCyMsZPtnXcXYO 7Z8+mIOP4p24RV6wfinMQBSJgQvBHmrL4g1iJAP86SaPzliHiFAzCZzma++5/g4uGsR7 a0wGEVcjdoz9mjfRmFRaSN97xKF45SO/lOkO0= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=/hihxsb5erPMsln/gUSY59M8NixzubgoudYMNGqOBjo=; b=RYhoRNvqP9lZgrhF6OS/zWnrL48R6AIf8e6pSYghQTHmVVmIOf2eNYWcGKNmlzHzG/ 6REjeevEc9tsW0jMB7tlLWQb4d7eXqg7EBGBvZJjXvlfw3KlKid8vK1i0PcyQY8AjjEx XJywm6yugo/Zjjt2k3ZqPAoJKL6QuDz4wbRYkbZzaGNtvOoThsNFDrxsINCiSQxG9MMb eO6hSwiRAq1upTHqOWz7sk3eOqWj+AviwZPmrXFclPfbvdyex+gjDAzBa9EwvbcdbPPK W1izk7wrxHuurb+MzUUXcXZCsUTU+fUWUCbuelX/cyabZ9WtHfmWDmDr/7r29QO42Tun l97g== X-Gm-Message-State: ANoB5pnPX2mB7nAsja82L0x4miJ8/0Ep26W2t+TC91IfVDLr5LFt3btt +I8+ybKFReHpuJ6xmhBhQgd4qtZJ70WFb1WkJOCiPrceC0Ria2vLnBSRZHFnecJaDCL+1obwRP5 BYwVbN6o/61Skh1x6FiIqsaX81mSH4H3wJY4ZOt+dQNEqjcPHCH43SQ4xtmwWn2SPw3IPpoG+VO VILohj7eFHC8+DUPRPHLAZU3BAug== X-Google-Smtp-Source: AA0mqf7ane6F6HV8dfwJ2yQM+5/9KGiO2ahYsgbLaINapHO2VdmgET/fKqtkbjCUGRl/lQ7GPaTwxw== X-Received: by 2002:a5d:4586:0:b0:242:1522:24a0 with SMTP id p6-20020a5d4586000000b00242152224a0mr24668948wrq.47.1671387550956; Sun, 18 Dec 2022 10:19:10 -0800 (PST) Received: from MacBook-Pro-6.lan ([2a0d:6fc2:218c:1a00:c45e:1c4b:fab4:ee34]) by smtp.gmail.com with ESMTPSA id b13-20020a05600003cd00b0024cb961b6aesm7956489wrg.104.2022.12.18.10.19.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 18 Dec 2022 10:19:10 -0800 (PST) From: david.keisarschm@mail.huji.ac.il To: linux-kernel@vger.kernel.org, Dave Hansen , Andy Lutomirski , Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, "H. Peter Anvin" Cc: Jason@zx2c4.com, David Keisar Schmidt , aksecurity@gmail.com, ilay.bahat1@gmail.com Subject: [PATCH v3 3/3] Replace invocation of weak PRNG in arch/x86/mm/kaslr.c Date: Sun, 18 Dec 2022 20:19:00 +0200 Message-Id: X-Mailer: git-send-email 2.38.0 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: David Keisar Schmidt This third series add some changes to the commit messages, and also replaces get_random_u32 with get_random_u32_below, in a case a modulo operation is done on the result. The memory randomization of the virtual address space of kernel memory regions (physical memory mapping, vmalloc & vmemmap) inside arch/x86/mm/kaslr.c is based on the function prandom_bytes_state which uses the prandom_u32 PRNG. However, this PRNG turned out to be weak, as noted in commit c51f8f88d705 To fix it, we have changed the invocation of prandom_bytes_state to get_random_bytes. Unlike get_random_bytes which maintains its own state, prandom_bytes state needs to be seeded, thus, we have omitted the call to the seeding function, since it is not needed anymore. # Changes since v2 * edited commit message. Signed-off-by: David Keisar Schmidt --- arch/x86/mm/kaslr.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-) diff --git a/arch/x86/mm/kaslr.c b/arch/x86/mm/kaslr.c index 557f0fe25..9ef8993d5 100644 --- a/arch/x86/mm/kaslr.c +++ b/arch/x86/mm/kaslr.c @@ -66,7 +66,6 @@ void __init kernel_randomize_memory(void) size_t i; unsigned long vaddr_start, vaddr; unsigned long rand, memory_tb; - struct rnd_state rand_state; unsigned long remain_entropy; unsigned long vmemmap_size; @@ -113,8 +112,6 @@ void __init kernel_randomize_memory(void) for (i = 0; i < ARRAY_SIZE(kaslr_regions); i++) remain_entropy -= get_padding(&kaslr_regions[i]); - prandom_seed_state(&rand_state, kaslr_get_random_long("Memory")); - for (i = 0; i < ARRAY_SIZE(kaslr_regions); i++) { unsigned long entropy; @@ -123,7 +120,7 @@ void __init kernel_randomize_memory(void) * available. */ entropy = remain_entropy / (ARRAY_SIZE(kaslr_regions) - i); - prandom_bytes_state(&rand_state, &rand, sizeof(rand)); + get_random_bytes(&rand, sizeof(rand)); entropy = (rand % (entropy + 1)) & PUD_MASK; vaddr += entropy; *kaslr_regions[i].base = vaddr; -- 2.38.0