From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 361AF8476 for ; Tue, 28 Mar 2023 14:53:15 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id AABC1C4339B; Tue, 28 Mar 2023 14:53:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1680015195; bh=yWPBRrFI/oYaXjmv3+o4pmMnCU+y0h1oA5LCrzYs3pg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=sdErljGFpi28qoCZbRZCliFS7R+2uccfjiCkAzbZ83/9rRngF3dTlYTR3PLhYUNpx 3kxdwof2Wp1C/u4mxH47e10bdV7p6qlEzRU01P73P6f2uLucdl4SJOZ5RVr8VNsGSI BugY/Fp+GOJRw2rsW9/n8oAb6egeD2AeJ1z9Aaak= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, =?UTF-8?q?Michal=20Koutn=C3=BD?= , Dave Hansen Subject: [PATCH 6.2 169/240] x86/mm: Do not shuffle CPU entry areas without KASLR Date: Tue, 28 Mar 2023 16:42:12 +0200 Message-Id: <20230328142626.702956348@linuxfoundation.org> X-Mailer: git-send-email 2.40.0 In-Reply-To: <20230328142619.643313678@linuxfoundation.org> References: <20230328142619.643313678@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Michal Koutný commit a3f547addcaa10df5a226526bc9e2d9a94542344 upstream. The commit 97e3d26b5e5f ("x86/mm: Randomize per-cpu entry area") fixed an omission of KASLR on CPU entry areas. It doesn't take into account KASLR switches though, which may result in unintended non-determinism when a user wants to avoid it (e.g. debugging, benchmarking). Generate only a single combination of CPU entry areas offsets -- the linear array that existed prior randomization when KASLR is turned off. Since we have 3f148f331814 ("x86/kasan: Map shadow for percpu pages on demand") and followups, we can use the more relaxed guard kasrl_enabled() (in contrast to kaslr_memory_enabled()). Fixes: 97e3d26b5e5f ("x86/mm: Randomize per-cpu entry area") Signed-off-by: Michal Koutný Signed-off-by: Dave Hansen Cc: stable@vger.kernel.org Link: https://lore.kernel.org/all/20230306193144.24605-1-mkoutny%40suse.com Signed-off-by: Greg Kroah-Hartman --- arch/x86/mm/cpu_entry_area.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/arch/x86/mm/cpu_entry_area.c b/arch/x86/mm/cpu_entry_area.c index 7316a8224259..e91500a80963 100644 --- a/arch/x86/mm/cpu_entry_area.c +++ b/arch/x86/mm/cpu_entry_area.c @@ -10,6 +10,7 @@ #include #include #include +#include static DEFINE_PER_CPU_PAGE_ALIGNED(struct entry_stack_page, entry_stack_storage); @@ -29,6 +30,12 @@ static __init void init_cea_offsets(void) unsigned int max_cea; unsigned int i, j; + if (!kaslr_enabled()) { + for_each_possible_cpu(i) + per_cpu(_cea_offset, i) = i; + return; + } + max_cea = (CPU_ENTRY_AREA_MAP_SIZE - PAGE_SIZE) / CPU_ENTRY_AREA_SIZE; /* O(sodding terrible) */ -- 2.40.0