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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id F1CCAC4332F for ; Thu, 22 Dec 2022 20:56:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235084AbiLVU4G (ORCPT ); Thu, 22 Dec 2022 15:56:06 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36552 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229668AbiLVU4F (ORCPT ); Thu, 22 Dec 2022 15:56:05 -0500 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 533421C93E for ; Thu, 22 Dec 2022 12:55:24 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1671742523; 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=lvRumMImlcFs3FZ95qQ7RqCaL1BsczRcfz4qHMe/Ro0=; b=AIVo5nuf4azU5OrZnODIJERGyv7FN3qXMAeDU9lkXnN9bMsygAPxdUklJzrx0pGMPz0Tt+ qEZ8mN/M/+CxI/ONa2//X41WRYE1oo5K82UjJPK8QA7JF1yUkz56Pu1QLtgRKrLrGndlCp KEsDP7nySkO4Z+3idoVg+//g7t2SFkM= 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-643-wBHk7L1HNYmRypQcJnJMyQ-1; Thu, 22 Dec 2022 15:55:18 -0500 X-MC-Unique: wBHk7L1HNYmRypQcJnJMyQ-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.rdu2.redhat.com [10.11.54.1]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id AA8FE101A521; Thu, 22 Dec 2022 20:55:17 +0000 (UTC) Received: from t480s.fritz.box (unknown [10.39.193.53]) by smtp.corp.redhat.com (Postfix) with ESMTP id 68BF340C2004; Thu, 22 Dec 2022 20:55:15 +0000 (UTC) From: David Hildenbrand To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, David Hildenbrand , Andrew Morton , Mike Kravetz , Peter Xu , Muchun Song , Miaohe Lin , stable@vger.kernel.org Subject: [PATCH v1 1/2] mm/hugetlb: fix PTE marker handling in hugetlb_change_protection() Date: Thu, 22 Dec 2022 21:55:10 +0100 Message-Id: <20221222205511.675832-2-david@redhat.com> In-Reply-To: <20221222205511.675832-1-david@redhat.com> References: <20221222205511.675832-1-david@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.1 on 10.11.54.1 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org There are two problematic cases when stumbling over a PTE marker in hugetlb_change_protection(): (1) We protect an uffd-wp PTE marker a second time using uffd-wp: we will end up in the "!huge_pte_none(pte)" case and mess up the PTE marker. (2) We unprotect a uffd-wp PTE marker: we will similarly end up in the "!huge_pte_none(pte)" case even though we cleared the PTE, because the "pte" variable is stale. We'll mess up the PTE marker. For example, if we later stumble over such a "wrongly modified" PTE marker, we'll treat it like a present PTE that maps some garbage page. This can, for example, be triggered by mapping a memfd backed by huge pages, registering uffd-wp, uffd-wp'ing an unmapped page and (a) uffd-wp'ing it a second time; or (b) uffd-unprotecting it; or (c) unregistering uffd-wp. Then, ff we trigger fallocate(FALLOC_FL_PUNCH_HOLE) on that file range, we will run into a VM_BUG_ON: [ 195.039560] page:00000000ba1f2987 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x0 [ 195.039565] flags: 0x7ffffc0001000(reserved|node=0|zone=0|lastcpupid=0x1fffff) [ 195.039568] raw: 0007ffffc0001000 ffffe742c0000008 ffffe742c0000008 0000000000000000 [ 195.039569] raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000 [ 195.039569] page dumped because: VM_BUG_ON_PAGE(compound && !PageHead(page)) [ 195.039573] ------------[ cut here ]------------ [ 195.039574] kernel BUG at mm/rmap.c:1346! [ 195.039579] invalid opcode: 0000 [#1] PREEMPT SMP NOPTI [ 195.039581] CPU: 7 PID: 4777 Comm: qemu-system-x86 Not tainted 6.0.12-200.fc36.x86_64 #1 [ 195.039583] Hardware name: LENOVO 20WNS1F81N/20WNS1F81N, BIOS N35ET50W (1.50 ) 09/15/2022 [ 195.039584] RIP: 0010:page_remove_rmap+0x45b/0x550 [ 195.039588] Code: [...] [ 195.039589] RSP: 0018:ffffbc03c3633ba8 EFLAGS: 00010292 [ 195.039591] RAX: 0000000000000040 RBX: ffffe742c0000000 RCX: 0000000000000000 [ 195.039592] RDX: 0000000000000002 RSI: ffffffff8e7aac1a RDI: 00000000ffffffff [ 195.039592] RBP: 0000000000000001 R08: 0000000000000000 R09: ffffbc03c3633a08 [ 195.039593] R10: 0000000000000003 R11: ffffffff8f146328 R12: ffff9b04c42754b0 [ 195.039594] R13: ffffffff8fcc6328 R14: ffffbc03c3633c80 R15: ffff9b0484ab9100 [ 195.039595] FS: 00007fc7aaf68640(0000) GS:ffff9b0bbf7c0000(0000) knlGS:0000000000000000 [ 195.039596] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 195.039597] CR2: 000055d402c49110 CR3: 0000000159392003 CR4: 0000000000772ee0 [ 195.039598] PKRU: 55555554 [ 195.039599] Call Trace: [ 195.039600] [ 195.039602] __unmap_hugepage_range+0x33b/0x7d0 [ 195.039605] unmap_hugepage_range+0x55/0x70 [ 195.039608] hugetlb_vmdelete_list+0x77/0xa0 [ 195.039611] hugetlbfs_fallocate+0x410/0x550 [ 195.039612] ? _raw_spin_unlock_irqrestore+0x23/0x40 [ 195.039616] vfs_fallocate+0x12e/0x360 [ 195.039618] __x64_sys_fallocate+0x40/0x70 [ 195.039620] do_syscall_64+0x58/0x80 [ 195.039623] ? syscall_exit_to_user_mode+0x17/0x40 [ 195.039624] ? do_syscall_64+0x67/0x80 [ 195.039626] entry_SYSCALL_64_after_hwframe+0x63/0xcd [ 195.039628] RIP: 0033:0x7fc7b590651f [ 195.039653] Code: [...] [ 195.039654] RSP: 002b:00007fc7aaf66e70 EFLAGS: 00000293 ORIG_RAX: 000000000000011d [ 195.039655] RAX: ffffffffffffffda RBX: 0000558ef4b7f370 RCX: 00007fc7b590651f [ 195.039656] RDX: 0000000018000000 RSI: 0000000000000003 RDI: 000000000000000c [ 195.039657] RBP: 0000000008000000 R08: 0000000000000000 R09: 0000000000000073 [ 195.039658] R10: 0000000008000000 R11: 0000000000000293 R12: 0000000018000000 [ 195.039658] R13: 00007fb8bbe00000 R14: 000000000000000c R15: 0000000000001000 [ 195.039661] Fix it by not going into the "!huge_pte_none(pte)" case if we stumble over an exclusive marker. spin_unlock() + continue would get the job done. However, instead, make it clearer that there are no fall-through statements: we process each case (hwpoison, migration, marker, !none, none) and then unlock the page table to continue with the next PTE. Let's avoid "continue" statements and use a single spin_unlock() at the end. Fixes: 60dfaad65aa9 ("mm/hugetlb: allow uffd wr-protect none ptes") Cc: Signed-off-by: David Hildenbrand --- mm/hugetlb.c | 21 +++++++-------------- 1 file changed, 7 insertions(+), 14 deletions(-) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 77f36e3681e3..3a94f519304f 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -6512,10 +6512,8 @@ unsigned long hugetlb_change_protection(struct vm_area_struct *vma, } pte = huge_ptep_get(ptep); if (unlikely(is_hugetlb_entry_hwpoisoned(pte))) { - spin_unlock(ptl); - continue; - } - if (unlikely(is_hugetlb_entry_migration(pte))) { + /* Nothing to do. */ + } else if (unlikely(is_hugetlb_entry_migration(pte))) { swp_entry_t entry = pte_to_swp_entry(pte); struct page *page = pfn_swap_entry_to_page(entry); @@ -6536,18 +6534,13 @@ unsigned long hugetlb_change_protection(struct vm_area_struct *vma, set_huge_pte_at(mm, address, ptep, newpte); pages++; } - spin_unlock(ptl); - continue; - } - if (unlikely(pte_marker_uffd_wp(pte))) { - /* - * This is changing a non-present pte into a none pte, - * no need for huge_ptep_modify_prot_start/commit(). - */ + } else if (unlikely(is_pte_marker(pte))) { + /* No other markers apply for now. */ + WARN_ON_ONCE(!pte_marker_uffd_wp(pte)); if (uffd_wp_resolve) + /* Safe to modify directly (non-present->none). */ huge_pte_clear(mm, address, ptep, psize); - } - if (!huge_pte_none(pte)) { + } else if (!huge_pte_none(pte)) { pte_t old_pte; unsigned int shift = huge_page_shift(hstate_vma(vma)); -- 2.38.1