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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 17659EB64D8 for ; Wed, 14 Jun 2023 18:43:52 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 8A5576B0074; Wed, 14 Jun 2023 14:43:51 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 855826B0075; Wed, 14 Jun 2023 14:43:51 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 71DC46B0078; Wed, 14 Jun 2023 14:43:51 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id 64C636B0074 for ; Wed, 14 Jun 2023 14:43:51 -0400 (EDT) Received: from smtpin28.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id 2B38A40742 for ; Wed, 14 Jun 2023 18:43:51 +0000 (UTC) X-FDA: 80902227462.28.21E098F Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by imf24.hostedemail.com (Postfix) with ESMTP id 66770180010 for ; Wed, 14 Jun 2023 18:43:49 +0000 (UTC) Authentication-Results: imf24.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=ZiRPIZzE; spf=pass (imf24.hostedemail.com: domain of lee@kernel.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=lee@kernel.org; dmarc=pass (policy=none) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1686768229; h=from:from:sender: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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=iAuaqMnCoaB3YmySrzfcGlXO3jvrdx/sMIvUMKJ1WtU=; b=VVDRtym+fmN5HI41q3C42msxewzpePeX8CzVFkyI8nkbkEzS6C9R2HJxRlVrw5PqLr77FU rG5U9FQvejXVjoGn4nPDBBWS2q7ofQkb/vWnaK9yaOiHbw2N8Fl4esMJjcefIlmK/lYAmC Drjtt1j4ayXLTNnFNKpyQd4wzGfjLLY= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1686768229; a=rsa-sha256; cv=none; b=ZZhaZ3Rvkg9itLrdJb8idKHULbm9h9vKAoBK2Lz2mloEp3gtaqtUxMAq4JNobjFau+Bcky U9A97HJqzExT967/maCYZjnK3SOQOimAbJ9+DGnxKT5Hmf0yb5xcsShE9HiPY9/Aq1ASEG v/XjhHKp03G+inOb+sJGV6FiMqFlorI= ARC-Authentication-Results: i=1; imf24.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=ZiRPIZzE; spf=pass (imf24.hostedemail.com: domain of lee@kernel.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=lee@kernel.org; dmarc=pass (policy=none) header.from=kernel.org Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 494E4645CA; Wed, 14 Jun 2023 18:43:48 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 14270C433C8; Wed, 14 Jun 2023 18:43:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1686768227; bh=NIXlB9+2WkBQ/E/Qxn+H6VTpQkwCpTesI9A9vvN9CeE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ZiRPIZzEq2FBbYrmRtsGLLdeSFFu9b8Q2J8fTocoPtIuJCnofrg1Bec5Yp2PbYOVp l/NO9PSsw60vOuWoKwlOJB4/NPA4/O9PYBMZXskmIOZ/65qF80usL6zzYvox32T6tF +v0gTMY9g9PgFXipLQ8f8Zo4l8B6QAkmclqRu3PMwMQG8rHyuZDvJ6w+gsToVoDMK7 AW9naZnVLIKx5dXQ28ot6P3H5Q+Q1/H0pKlQ9KWr5nH7adquqZ54HGh+0NXrKfs5U3 OdvGZfwKz6jDYoV4MOFpRXv63LJs/Rp5zjJ40kIBSb6v/f016GGtDZG/N5SZ3ymDQU c6z9G9ehSeqWA== Date: Wed, 14 Jun 2023 19:43:41 +0100 From: Lee Jones To: Nick Desaulniers Cc: dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 1/1] x86/mm/KASLR: Store pud_page_tramp into entry rather than page Message-ID: <20230614184341.GC3635807@google.com> References: <20230614163859.924309-1-lee@kernel.org> <20230614163859.924309-2-lee@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Stat-Signature: uhx4ergq4sits4eyykbk4k77cjanrpta X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 66770180010 X-Rspam-User: X-HE-Tag: 1686768229-434867 X-HE-Meta: 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 UDWFbJQK FK4Aaw/KiQqHNIuF0Zeko9/EQLplF6ZIn5SisUN9DwAOPr+2mg6paBsmNtd8VLIoSE3NjxwaTF4sbY/LVbBGgx9473lCZbyKI0eEKQSbK0Q62wlfCtggoad4diFEXNiNOvyTHd8W46asGvfBNDsFzlSkxXbtLwx3ufx8h33F/3dNXeuyO4GPSroC/c6UnffkzjiAaVyzQbjqQpCehBy+NbQM508nhv660tBrowqo5wNIhKT9X3ottntLGn6SJawdhtZcMkVv/VklgTSGjLs6MPkPSsm8fCik97pbtw43xezftFSKsOG9YWLPSHuxWlQXHjbn0wnFigIvefa+KIHswrN4FwtEDMBshN/FT4Y8HH0sgD7KmeLNJMAPPwkyRPtcVUBp/OU9DPXrbQjEAey6PIKjxCMVQKjoBE/Qj X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, 14 Jun 2023, Nick Desaulniers wrote: > On Wed, Jun 14, 2023 at 05:38:54PM +0100, Lee Jones wrote: > > set_pgd() expects to be passed whole pages to operate on, whereas > > trampoline_pgd_entry is, as the name suggests, an entry. The > > ramifications for using set_pgd() here are that the following thread of > > execution will not only place the suggested value into the > > trampoline_pgd_entry (8-Byte globally stored [.bss]) variable, PTI will > > also attempt to replicate that value into the non-existent neighboring > > user page (located +4k away), leading to the corruption of other global > > [.bss] stored variables. > > > > Suggested-by: Dave Hansen > > Signed-off-by: Lee Jones > > Nice work tracking this one down! > > Fixes: 0925dda5962e ("x86/mm/KASLR: Use only one PUD entry for real mode trampoline") > Cc: I was planning on backporting this myself once it hits Mainline. Happy to submit a RESEND with those pieces added if required though. Or perhaps someone would be kind enough to add them on merge? > > --- > > 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 557f0fe25dff4..37db264866b64 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)); > > } > > } > > -- > > 2.41.0.162.gfafddb0af9-goog > > -- Lee Jones [李琼斯]