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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 47DD0D3A66B for ; Tue, 29 Oct 2024 15:08:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=U/l2svaTzZ+AiDvUzyRRzZRqHQoQCXsogemwGjfJUps=; b=Dr2d1fI9bvqrO1Ofe0ff58Uda8 KOUMqWsiIWUQHQ1RzOj4MLMiba0x3yRAnQWyg9f9ERRV5yMFTp4Kp2sfrAscpp4FY5dzIwwEJC6Ta Mj3B7z0Ji0Rd/VS6Qe6pJ8nRrhiQnoQARDLXQkNm6wrpGHFk52zGCIi8clADReDVj4buC7PVQUHnu CpsJDxFqjUTnu6dfjUUixjHutYz3As53dknQ10zxgliEhFaRG+F0QpGJmry25Hesfl+twRyqqEnCb KEPkwNj+Zx1v1YgpSOj5LcxaevNUYKprZFG3O7hgBsZ/EWx6J0YFXQEYWiPJDSh9u2cDZtNvWqxPJ EXaXdWGg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1t5npY-0000000EpyM-35cS; Tue, 29 Oct 2024 15:08:24 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1t5nm3-0000000EoSU-2y6o for linux-arm-kernel@lists.infradead.org; Tue, 29 Oct 2024 15:04:49 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id DDC51113E; Tue, 29 Oct 2024 08:05:14 -0700 (PDT) Received: from arm.com (usa-sjc-mx-foss1.foss.arm.com [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 754203F73B; Tue, 29 Oct 2024 08:04:43 -0700 (PDT) Date: Tue, 29 Oct 2024 15:04:41 +0000 From: Catalin Marinas To: Lorenzo Stoakes Cc: Vlastimil Babka , Linus Torvalds , "Liam R. Howlett" , Mark Brown , Andrew Morton , Jann Horn , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Peter Xu , linux-arm-kernel@lists.infradead.org, Will Deacon , Aishwarya TCV Subject: Re: [PATCH hotfix 6.12 v2 4/8] mm: resolve faulty mmap_region() error path behaviour Message-ID: References: <438f50c5-8b8c-444f-ae85-10e5151f3f24@lucifer.local> <57mgmdx7wgfwci3yo3ggkmcnm3ujamgkwcccm77ypvmer5tegn@opiq3ceh2uvy> <0b64edb9-491e-4dcd-8dc1-d3c8a336a49b@suse.cz> <1608957a-d138-4401-98ef-7fbe5fb7c387@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20241029_080447_864164_982535D0 X-CRM114-Status: GOOD ( 28.24 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Lorenzo, Thanks for trying to fix this. On Mon, Oct 28, 2024 at 10:14:50PM +0000, Lorenzo Stoakes wrote: > From 247003cd2a4b5f4fc2dac97f5ef7e473a47f4324 Mon Sep 17 00:00:00 2001 > From: Lorenzo Stoakes > Date: Mon, 28 Oct 2024 22:05:44 +0000 > Subject: [PATCH] mm: perform MTE check within arm64 hook entirely > > It doesn't make sense to have shmem explicitly check this one arch-specific > case, it is arch-specific, so the arch should handle it. We know shmem is a > case in which we want to permit MTE, so simply check for this directly. > > This also fixes the issue with checking arch_validate_flags() early, which > would otherwise break mmap_region(). > > In order to implement this we must pass a file pointer, and additionally > update the sparc code to accept this parameter too. > > We'd ideally like to have eliminated the arch_calc_vm_flag_bits() case, but > we risk inadvertently changing behaviour as we do not have mmap() flags > available at the point of the arch_validate_flags() check and a MAP_ANON | > MAP_HUGETLB case would be accepted for MTE currently, but a MAP_SHARED | > MAP_HUGETLB would not. > > This is likely an oversight but we want to try to keep behaviour identical > to before in this patch. MAP_HUGETLB support for MTE is only in -next currently, so there wouldn't be any ABI change if we also allowed MAP_SHARED | MAP_HUGETLB. In 6.12, MAP_HUGETLB is not allowed to have PROT_MTE. > So continue to check VM_MTE_ALLOWED which arch_calc_vm_flag_bits() sets if > MAP_ANON. [...] > diff --git a/mm/shmem.c b/mm/shmem.c > index 4ba1d00fabda..e87f5d6799a7 100644 > --- a/mm/shmem.c > +++ b/mm/shmem.c > @@ -2733,9 +2733,6 @@ static int shmem_mmap(struct file *file, struct vm_area_struct *vma) > if (ret) > return ret; > > - /* arm64 - allow memory tagging on RAM-based files */ > - vm_flags_set(vma, VM_MTE_ALLOWED); This breaks arm64 KVM if the VMM uses shared mappings for the memory slots (which is possible). We have kvm_vma_mte_allowed() that checks for the VM_MTE_ALLOWED flag as the VMM may not use PROT_MTE/VM_MTE directly. I need to read this thread properly but why not pass the file argument to arch_calc_vm_flag_bits() and set VM_MTE_ALLOWED in there? -- Catalin