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[2620:137:e000::1:20]) by mx.google.com with ESMTP id mj15-20020a17090b368f00b00257482b1795si2098826pjb.166.2023.06.16.12.02.00; Fri, 16 Jun 2023 12:02:14 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@linutronix.de header.s=2020 header.b=uOLoSFEh; dkim=neutral (no key) header.i=@linutronix.de; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=linutronix.de Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345372AbjFPSxj (ORCPT + 99 others); Fri, 16 Jun 2023 14:53:39 -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 X-Spam-Status: No, score=-4.4 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_MED,SPF_HELO_NONE, SPF_PASS,T_SCC_BODY_TEXT_LINE,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1768887035641588630?= X-GMAIL-MSGID: =?utf-8?q?1768887035641588630?= The following commit has been merged into the x86/urgent branch of tip: Commit-ID: d082d48737c75d2b3cc1f972b8c8674c25131534 Gitweb: https://git.kernel.org/tip/d082d48737c75d2b3cc1f972b8c8674c25131534 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 trampoline") 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))); - set_pgd(&trampoline_pgd_entry, - __pgd(_KERNPG_TABLE | __pa(p4d_page_tramp))); + trampoline_pgd_entry = + __pgd(_KERNPG_TABLE | __pa(p4d_page_tramp)); } else { - set_pgd(&trampoline_pgd_entry, - __pgd(_KERNPG_TABLE | __pa(pud_page_tramp))); + trampoline_pgd_entry = + __pgd(_KERNPG_TABLE | __pa(pud_page_tramp)); } }