From nobody Sun Feb 8 11:22:12 2026 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 840B5EB64D7 for ; Fri, 16 Jun 2023 18:53:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345381AbjFPSxk (ORCPT ); Fri, 16 Jun 2023 14:53:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34084 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1345201AbjFPSxa (ORCPT ); Fri, 16 Jun 2023 14:53:30 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1CB9E3AA5; Fri, 16 Jun 2023 11:53:23 -0700 (PDT) Date: Fri, 16 Jun 2023 18:53:20 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1686941601; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=8bt6GbZy0AVDBFsEt7a+yTKmNBsrum7dVB7lreI8D7I=; b=uOLoSFEhMiB6o0KB3odoVIpJ7PtKMKj23lrAWdjvbsDojANzr0ckETCVz3w13UsY2zWGiz co0BrIIOJk6YgvOJ0aPNygXqmb2jQs26Yqlzu6/8eEFpoOSy5pIirl5b/WJiIGVKoKyvsr Wcne8GA9jBJjKqiceRXdO4Ync+SHPKOwBgS6XoRKV+aAy1Bd33GXb7OBN+JLg7PeiFiad+ 0v32Nj/FYukYJiAYWTVS20uX7408oYBhHI7ZOhVouG+vgDsJSOcASCqZUpkiOZphp0dAsq B8zFIxrRMZIPfCVXfWxpGVIS84om4VZ5c+JpfpHTIIewiWOBG+C7Alsi1Hu3wg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1686941601; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=8bt6GbZy0AVDBFsEt7a+yTKmNBsrum7dVB7lreI8D7I=; b=O+2eFfmNGCjG7iHNV3zvBNjYblfyfKXyjMU/ag1VmkG8HGvyV0LZr1o8gtTIwTD9XoZilA PHomy39TRq6dMSAg== From: "tip-bot2 for Lee Jones" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: x86/urgent] x86/mm: Avoid using set_pgd() outside of real PGD pages Cc: Dave Hansen , Lee Jones , , x86@kernel.org, linux-kernel@vger.kernel.org MIME-Version: 1.0 Message-ID: <168694160067.404.13343792487331756749.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the x86/urgent branch of tip: Commit-ID: d082d48737c75d2b3cc1f972b8c8674c25131534 Gitweb: https://git.kernel.org/tip/d082d48737c75d2b3cc1f972b8c8674c2= 5131534 Author: Lee Jones AuthorDate: Wed, 14 Jun 2023 17:38:54 +01:00 Committer: Dave Hansen CommitterDate: Fri, 16 Jun 2023 11:46:42 -07:00 x86/mm: Avoid using set_pgd() outside of real PGD pages KPTI keeps around two PGDs: one for userspace and another for the kernel. Among other things, set_pgd() contains infrastructure to ensure that updates to the kernel PGD are reflected in the user PGD as well. One side-effect of this is that set_pgd() expects to be passed whole pages. Unfortunately, init_trampoline_kaslr() passes in a single entry: 'trampoline_pgd_entry'. When KPTI is on, set_pgd() will update 'trampoline_pgd_entry' (an 8-Byte globally stored [.bss] variable) and will then proceed to replicate that value into the non-existent neighboring user page (located +4k away), leading to the corruption of other global [.bss] stored variables. Fix it by directly assigning 'trampoline_pgd_entry' and avoiding set_pgd(). [ dhansen: tweak subject and changelog ] Fixes: 0925dda5962e ("x86/mm/KASLR: Use only one PUD entry for real mode tr= ampoline") Suggested-by: Dave Hansen Signed-off-by: Lee Jones Signed-off-by: Dave Hansen Cc: Link: https://lore.kernel.org/all/20230614163859.924309-1-lee@kernel.org/g --- arch/x86/mm/kaslr.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/arch/x86/mm/kaslr.c b/arch/x86/mm/kaslr.c index 557f0fe..37db264 100644 --- a/arch/x86/mm/kaslr.c +++ b/arch/x86/mm/kaslr.c @@ -172,10 +172,10 @@ void __meminit init_trampoline_kaslr(void) set_p4d(p4d_tramp, __p4d(_KERNPG_TABLE | __pa(pud_page_tramp))); =20 - set_pgd(&trampoline_pgd_entry, - __pgd(_KERNPG_TABLE | __pa(p4d_page_tramp))); + trampoline_pgd_entry =3D + __pgd(_KERNPG_TABLE | __pa(p4d_page_tramp)); } else { - set_pgd(&trampoline_pgd_entry, - __pgd(_KERNPG_TABLE | __pa(pud_page_tramp))); + trampoline_pgd_entry =3D + __pgd(_KERNPG_TABLE | __pa(pud_page_tramp)); } }