From patchwork Mon Nov 7 16:17:25 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Hildenbrand X-Patchwork-Id: 13034783 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 gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (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 22AAEC4332F for ; Mon, 7 Nov 2022 16:18:36 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 4895F10E466; Mon, 7 Nov 2022 16:18:34 +0000 (UTC) Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by gabe.freedesktop.org (Postfix) with ESMTPS id 1515310E45C for ; Mon, 7 Nov 2022 16:18:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1667837898; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=jDk9bhO7j0dBiRTBonVIWKZ9rsqO0bmea9iIm0D/070=; b=CfGjtaYLGcc1bzNn9QAa4mw7O3F3UtoJ34pMf0D7LmObLSJhxT34T5LatRZgOuzaEMuoNg 98ydNdV/EJ5ZJKlyXS5KZiXwyxKRlE+azFuauQko0312KTOM1TDSVxdNCjoJKNFuzlRzrC mHp6ChJoF0WeqvK5sYjv4ptVVDLorxw= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-316-TGbR2pUAPIyw3MgPlt6EzA-1; Mon, 07 Nov 2022 11:18:13 -0500 X-MC-Unique: TGbR2pUAPIyw3MgPlt6EzA-1 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id D2455857FAB; Mon, 7 Nov 2022 16:18:11 +0000 (UTC) Received: from t480s.redhat.com (unknown [10.39.195.106]) by smtp.corp.redhat.com (Postfix) with ESMTP id 497EF4B3FC6; Mon, 7 Nov 2022 16:18:05 +0000 (UTC) From: David Hildenbrand To: linux-kernel@vger.kernel.org Subject: [PATCH RFC 04/19] mm: add early FAULT_FLAG_UNSHARE consistency checks Date: Mon, 7 Nov 2022 17:17:25 +0100 Message-Id: <20221107161740.144456-5-david@redhat.com> In-Reply-To: <20221107161740.144456-1-david@redhat.com> References: <20221107161740.144456-1-david@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.9 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: David Hildenbrand , dri-devel@lists.freedesktop.org, linux-mm@kvack.org, Nadav Amit , linux-kselftest@vger.kernel.org, Andrea Arcangeli , linux-samsung-soc@vger.kernel.org, linux-rdma@vger.kernel.org, Hugh Dickins , Matthew Wilcox , Jason Gunthorpe , linux-arm-kernel@lists.infradead.org, linux-media@vger.kernel.org, Arnd Bergmann , John Hubbard , etnaviv@lists.freedesktop.org, Peter Xu , Muchun Song , Vlastimil Babka , Greg Kroah-Hartman , Oded Gabbay , Andrew Morton , Linus Torvalds , Mike Kravetz Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" For now, FAULT_FLAG_UNSHARE only applies to anonymous pages, which implies a COW mapping. Let's hide FAULT_FLAG_UNSHARE early if we're not dealing with a COW mapping, such that we treat it like a read fault as documented and don't have to worry about the flag throughout all fault handlers. While at it, centralize the check for mutual exclusion of FAULT_FLAG_UNSHARE and FAULT_FLAG_WRITE and just drop the check that either flag is set in the WP handler. Signed-off-by: David Hildenbrand --- mm/huge_memory.c | 3 --- mm/hugetlb.c | 5 ----- mm/memory.c | 23 ++++++++++++++++++++--- 3 files changed, 20 insertions(+), 11 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 1d47b3f7b877..7173756d6868 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1267,9 +1267,6 @@ vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf) vmf->ptl = pmd_lockptr(vma->vm_mm, vmf->pmd); VM_BUG_ON_VMA(!vma->anon_vma, vma); - VM_BUG_ON(unshare && (vmf->flags & FAULT_FLAG_WRITE)); - VM_BUG_ON(!unshare && !(vmf->flags & FAULT_FLAG_WRITE)); - if (is_huge_zero_pmd(orig_pmd)) goto fallback; diff --git a/mm/hugetlb.c b/mm/hugetlb.c index be572af75d9c..3672c7e06748 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -5316,9 +5316,6 @@ static vm_fault_t hugetlb_wp(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long haddr = address & huge_page_mask(h); struct mmu_notifier_range range; - VM_BUG_ON(unshare && (flags & FOLL_WRITE)); - VM_BUG_ON(!unshare && !(flags & FOLL_WRITE)); - /* * hugetlb does not support FOLL_FORCE-style write faults that keep the * PTE mapped R/O such as maybe_mkwrite() would do. @@ -5328,8 +5325,6 @@ static vm_fault_t hugetlb_wp(struct mm_struct *mm, struct vm_area_struct *vma, /* Let's take out MAP_SHARED mappings first. */ if (vma->vm_flags & VM_MAYSHARE) { - if (unlikely(unshare)) - return 0; set_huge_ptep_writable(vma, haddr, ptep); return 0; } diff --git a/mm/memory.c b/mm/memory.c index 78e2c58f6f31..fe131273217a 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3343,9 +3343,6 @@ static vm_fault_t do_wp_page(struct vm_fault *vmf) struct vm_area_struct *vma = vmf->vma; struct folio *folio; - VM_BUG_ON(unshare && (vmf->flags & FAULT_FLAG_WRITE)); - VM_BUG_ON(!unshare && !(vmf->flags & FAULT_FLAG_WRITE)); - if (likely(!unshare)) { if (userfaultfd_pte_wp(vma, *vmf->pte)) { pte_unmap_unlock(vmf->pte, vmf->ptl); @@ -5150,6 +5147,22 @@ static void lru_gen_exit_fault(void) } #endif /* CONFIG_LRU_GEN */ +static vm_fault_t sanitize_fault_flags(struct vm_area_struct *vma, + unsigned int *flags) +{ + if (unlikely(*flags & FAULT_FLAG_UNSHARE)) { + if (WARN_ON_ONCE(*flags & FAULT_FLAG_WRITE)) + return VM_FAULT_SIGSEGV; + /* + * FAULT_FLAG_UNSHARE only applies to COW mappings. Let's + * just treat it like an ordinary read-fault otherwise. + */ + if (!is_cow_mapping(vma->vm_flags)) + *flags &= ~FAULT_FLAG_UNSHARE; + } + return 0; +} + /* * By the time we get here, we already hold the mm semaphore * @@ -5166,6 +5179,10 @@ vm_fault_t handle_mm_fault(struct vm_area_struct *vma, unsigned long address, count_vm_event(PGFAULT); count_memcg_event_mm(vma->vm_mm, PGFAULT); + ret = sanitize_fault_flags(vma, &flags); + if (ret) + return ret; + if (!arch_vma_access_permitted(vma, flags & FAULT_FLAG_WRITE, flags & FAULT_FLAG_INSTRUCTION, flags & FAULT_FLAG_REMOTE))