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]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id E5470C5CFDB for ; Thu, 13 Aug 2026 09:46:16 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id CC8EB6B045E; Thu, 13 Aug 2026 05:46:15 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id CA0746B045F; Thu, 13 Aug 2026 05:46:15 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id BB6E66B0460; Thu, 13 Aug 2026 05:46:15 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 999416B045E for ; Thu, 13 Aug 2026 05:46:15 -0400 (EDT) Received: from smtpin04.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay05.hostedemail.com (Postfix) with ESMTP id 3720A405B8 for ; Thu, 13 Aug 2026 09:46:15 +0000 (UTC) X-FDA: 85095765510.04.D4C62CD Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf18.hostedemail.com (Postfix) with ESMTP id A0E751C0006 for ; Thu, 13 Aug 2026 09:46:13 +0000 (UTC) Authentication-Results: imf18.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=DKnQd5xl; spf=pass (imf18.hostedemail.com: domain of ljs@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=ljs@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1786614373; 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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=+x2tiBGgnfXYaaYiZV+xganvGkJiR/qvbRK36a01nqA=; b=XzlZiyKMt1fczTq47Aku+UKA5d5rcmSY9iYNIArod5xE0cveNUob4B4zRxla0rC7Yn6Jhn 96Jyda2StCgfHgeM9XXspVN7Q2Jm4lb2NDVCRrwWKohcOoOV3dd1ifgN1BFQGxsYoxoK5w MxFTXRzE+i05I3go5Ywz0IxHJTGIJ7U= ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1786614373; b=AovNu0yngils0T8PE1PCeZLsdH3EZdkJoYtte3jnlnPa8vcPMKliBRgc8RJfXbb/UJw/f4 gJnvAy5ZwmRsNt638m967GuOt4gaDNVhCdv2Td84JSwPW/TseeNpIpgB8cQL2dRMQuc/P4 spITbnsUbbL//n/os5kGr6aOs6K8Jfw= ARC-Authentication-Results: i=1; imf18.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=DKnQd5xl; spf=pass (imf18.hostedemail.com: domain of ljs@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=ljs@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 22C2E6011F; Thu, 13 Aug 2026 09:46:13 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 60D021F00A3A; Thu, 13 Aug 2026 09:46:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1786614372; bh=+x2tiBGgnfXYaaYiZV+xganvGkJiR/qvbRK36a01nqA=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=DKnQd5xlGQw8aHszKjwfbFCCC8y3Y7nwaZ0WSBdqVQgD7c4L39ViTScf20Tx2H0Tc qSF5ay3tU4XMK8P3l9UG03o2FhYZZGlQK3EmSVggbqr6RVQV5wTpZQQSMBgqoVpnHY /auQxWhMNLIDXnBsrBUjwNIgBOb0koxdy77mBXjQWwZRY+scOqG7bbIFoehCaqw8CT +zLSgJUul/UYABxCySVnf8x2W0XiJA+JayL1r34pqVMZTLIOj6OKxlqkvUTqRv4LrR /ZHKqBbBbam8hdsA/SdaE0v/ew0RIVcBt2IA+buPMpHBD4Opr6/oxZiQAcquf3MPAT S178E9QyFkVAg== Date: Thu, 13 Aug 2026 10:45:48 +0100 From: "Lorenzo Stoakes (ARM)" To: "Mike Rapoport (Microsoft)" Cc: Dave Hansen , Andrew Morton , Andy Lutomirski , Borislav Petkov , David CARLIER , David Hildenbrand , Ingo Molnar , Jason Gunthorpe , Jiri Slaby , Juergen Gross , Kevin Tian , Kiryl Shutsemau , "Liam R. Howlett" , Lu Baolu , Nikunj A Dadhania , Pedro Falcato , "H. Peter Anvin" , Peter Zijlstra , Shakeel Butt , Steffen Dirkwinkel , Suren Baghdasaryan , Thomas Gleixner , Toshi Kani , Vishal Moola , Vlastimil Babka , Will Deacon , iommu@lists.linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org, stable@vger.kernel.org, syzbot@syzkaller.appspotmail.com, x86@kernel.org Subject: Re: [PATCH v2 5/5] x86/mm/pat: fix effective RW computation in lookup_address_in_pgd_attr() Message-ID: References: <20260813-cpa-fixes-v2-0-39b4ff90f91d@kernel.org> <20260813-cpa-fixes-v2-5-39b4ff90f91d@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260813-cpa-fixes-v2-5-39b4ff90f91d@kernel.org> X-Rspam-User: X-Stat-Signature: 7fmasj96qyrg3sp3g3ean6xxdw9d6kuu X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: A0E751C0006 X-HE-Tag: 1786614373-365506 X-HE-Meta: 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 fy14iy2k 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Aug 13, 2026 at 12:01:28PM +0300, Mike Rapoport (Microsoft) wrote: > lookup_address_in_pgd_attr() accumulates the effective NX and RW bits of > the walked page table levels so that verify_rwx() can detect mappings that > are both writable and executable. > > The RW bits are folded into a bool with > > rw &= pXd_flags(*pXd) & _PAGE_RW; > > but _PAGE_RW is 0x2. So consider the accumulation line: > > rw &= pXd_flags(*pXd) & _PAGE_RW; > > where rw=0x1 and the right side evaluates down to 0x2. It'll end up doing: > > rw = 0x1 & 0x2 > > and rw always ends up 0. > > This way rw becomes false at the first level walked, regardless of the > actual permissions, and verify_rwx() treats every mapping as non-writable > and never reports a W^X violation. > > Add double negation to the right side to normalize the _PAGE_RW flag to > 0 or 1. > > Fixes: ceb647b4b529 ("x86/pat: Introduce lookup_address_in_pgd_attr()") > Cc: stable@vger.kernel.org > Assisted-by: Copilot:claude-opus-4.8 > Reviewed-by: Juergen Gross > Tested-by: syzbot@syzkaller.appspotmail.com > Signed-off-by: Mike Rapoport (Microsoft) Yikes, good find! LGTM so: Reviewed-by: Lorenzo Stoakes (ARM) > --- > arch/x86/mm/pat/set_memory.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c > index fbc418dfc597..430d0b448371 100644 > --- a/arch/x86/mm/pat/set_memory.c > +++ b/arch/x86/mm/pat/set_memory.c > @@ -754,7 +754,7 @@ pte_t *lookup_address_in_pgd_attr(pgd_t *pgd, unsigned long address, > > *level = PG_LEVEL_512G; > *nx |= pgd_flags(*pgd) & _PAGE_NX; > - *rw &= pgd_flags(*pgd) & _PAGE_RW; > + *rw &= !!(pgd_flags(*pgd) & _PAGE_RW); > > p4d = p4d_offset(pgd, address); > if (p4d_none(*p4d)) > @@ -765,7 +765,7 @@ pte_t *lookup_address_in_pgd_attr(pgd_t *pgd, unsigned long address, > > *level = PG_LEVEL_1G; > *nx |= p4d_flags(*p4d) & _PAGE_NX; > - *rw &= p4d_flags(*p4d) & _PAGE_RW; > + *rw &= !!(p4d_flags(*p4d) & _PAGE_RW); > > pud = pud_offset(p4d, address); > if (pud_none(*pud)) > @@ -776,7 +776,7 @@ pte_t *lookup_address_in_pgd_attr(pgd_t *pgd, unsigned long address, > > *level = PG_LEVEL_2M; > *nx |= pud_flags(*pud) & _PAGE_NX; > - *rw &= pud_flags(*pud) & _PAGE_RW; > + *rw &= !!(pud_flags(*pud) & _PAGE_RW); > > pmd = pmd_offset(pud, address); > if (pmd_none(*pmd)) > @@ -787,7 +787,7 @@ pte_t *lookup_address_in_pgd_attr(pgd_t *pgd, unsigned long address, > > *level = PG_LEVEL_4K; > *nx |= pmd_flags(*pmd) & _PAGE_NX; > - *rw &= pmd_flags(*pmd) & _PAGE_RW; > + *rw &= !!(pmd_flags(*pmd) & _PAGE_RW); > > return pte_offset_kernel(pmd, address); > } > > -- > 2.53.0 > -- Cheers, Lorenzo