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 X-Spam-Level: X-Spam-Status: No, score=-10.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E5631C433FC for ; Mon, 27 Jul 2020 14:18:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BF8D920775 for ; Mon, 27 Jul 2020 14:18:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1595859487; bh=6rrJ4vF0KkOU6fgx8VcLlGCgvhfHnsigbaZGsxfaHaU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=DC0DsSpCj+efWpvMnOldmffrTlCCJekJNv9dFtJ3Z5Oj/BkaopaOJbqzVIloxL6Z1 IreGXbHY/ArMh8jG7l01V3n44jWPvPcC8pw/3+4GzCUS0qMrXubnfT3LxIypMgK46w fHqYkJo5q/uNCk5RjDdIdCdL8O7Erxdfr93884oo= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731168AbgG0OSG (ORCPT ); Mon, 27 Jul 2020 10:18:06 -0400 Received: from mail.kernel.org ([198.145.29.99]:45548 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731147AbgG0OSB (ORCPT ); Mon, 27 Jul 2020 10:18:01 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 992EC2070A; Mon, 27 Jul 2020 14:18:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1595859481; bh=6rrJ4vF0KkOU6fgx8VcLlGCgvhfHnsigbaZGsxfaHaU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Go7Bi6U2igMkDFDUgkc+qgrrJPttQEacVoR+swfDqMUXqtD67/64oZWMZTmGKL8bj IslHqP3UkQ0E2l757VI+83Kgi2VKEh4fFhFL41dhaun5RViSJrYxlkLqKttJCKrSvq LF6jRJ8Xk+a5KIYYIFPVChVhP4oyQEskLxex9qN4= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, syzbot+ed318e8b790ca72c5ad0@syzkaller.appspotmail.com, "Kirill A. Shutemov" , Andrew Morton , David Hildenbrand , Yang Shi , Linus Torvalds Subject: [PATCH 5.4 125/138] khugepaged: fix null-pointer dereference due to race Date: Mon, 27 Jul 2020 16:05:20 +0200 Message-Id: <20200727134931.680601862@linuxfoundation.org> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20200727134925.228313570@linuxfoundation.org> References: <20200727134925.228313570@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Kirill A. Shutemov commit 594cced14ad3903166c8b091ff96adac7552f0b3 upstream. khugepaged has to drop mmap lock several times while collapsing a page. The situation can change while the lock is dropped and we need to re-validate that the VMA is still in place and the PMD is still subject for collapse. But we miss one corner case: while collapsing an anonymous pages the VMA could be replaced with file VMA. If the file VMA doesn't have any private pages we get NULL pointer dereference: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] anon_vma_lock_write include/linux/rmap.h:120 [inline] collapse_huge_page mm/khugepaged.c:1110 [inline] khugepaged_scan_pmd mm/khugepaged.c:1349 [inline] khugepaged_scan_mm_slot mm/khugepaged.c:2110 [inline] khugepaged_do_scan mm/khugepaged.c:2193 [inline] khugepaged+0x3bba/0x5a10 mm/khugepaged.c:2238 The fix is to make sure that the VMA is anonymous in hugepage_vma_revalidate(). The helper is only used for collapsing anonymous pages. Fixes: 99cb0dbd47a1 ("mm,thp: add read-only THP support for (non-shmem) FS") Reported-by: syzbot+ed318e8b790ca72c5ad0@syzkaller.appspotmail.com Signed-off-by: Kirill A. Shutemov Signed-off-by: Andrew Morton Reviewed-by: David Hildenbrand Acked-by: Yang Shi Cc: Link: http://lkml.kernel.org/r/20200722121439.44328-1-kirill.shutemov@linux.intel.com Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/khugepaged.c | 3 +++ 1 file changed, 3 insertions(+) --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -876,6 +876,9 @@ static int hugepage_vma_revalidate(struc return SCAN_ADDRESS_RANGE; if (!hugepage_vma_check(vma, vma->vm_flags)) return SCAN_VMA_CHECK; + /* Anon VMA expected */ + if (!vma->anon_vma || vma->vm_ops) + return SCAN_VMA_CHECK; return 0; }