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=-7.0 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,URIBL_BLOCKED autolearn=no 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 01EF4C433DF for ; Fri, 24 Jul 2020 04:15:37 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id BB4032067D for ; Fri, 24 Jul 2020 04:15:36 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="gEM/Nx1j" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BB4032067D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 6615B8D000F; Fri, 24 Jul 2020 00:15:36 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 5E8A78D0007; Fri, 24 Jul 2020 00:15:36 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 525678D000F; Fri, 24 Jul 2020 00:15:36 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0004.hostedemail.com [216.40.44.4]) by kanga.kvack.org (Postfix) with ESMTP id 3CE198D0007 for ; Fri, 24 Jul 2020 00:15:36 -0400 (EDT) Received: from smtpin07.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id EFF5593CA for ; Fri, 24 Jul 2020 04:15:35 +0000 (UTC) X-FDA: 77071655430.07.day32_390247526f44 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin07.hostedemail.com (Postfix) with ESMTP id CCB661802BACA for ; Fri, 24 Jul 2020 04:15:35 +0000 (UTC) X-HE-Tag: day32_390247526f44 X-Filterd-Recvd-Size: 3549 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf44.hostedemail.com (Postfix) with ESMTP for ; Fri, 24 Jul 2020 04:15:35 +0000 (UTC) Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (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 6C9432065F; Fri, 24 Jul 2020 04:15:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1595564134; bh=b0W4lX8wbjuHM2Nxb8mh+HiplDl7+Q8TqMh+NXBorwU=; h=Date:From:To:Subject:In-Reply-To:From; b=gEM/Nx1jMDCEoNblHf5Fw/QhLEvEW/rmUjCW1Ij5T++aMv63BdKlFLQRCULGRLMIJ uPCHSLtXDhVPvihtgwCBfa9M6v4CcA4CGhnCkBM8dHzTQGNC7l2AkOmlfOmQXnTApA B2i0ha8DfCPrMCu3ZI55PNdfPoeILxQYT/RDRJkU= Date: Thu, 23 Jul 2020 21:15:34 -0700 From: Andrew Morton To: akpm@linux-foundation.org, david@redhat.com, kirill.shutemov@linux.intel.com, linux-mm@kvack.org, mm-commits@vger.kernel.org, stable@vger.kernel.org, torvalds@linux-foundation.org, yang.shi@linux.alibaba.com Subject: [patch 09/15] khugepaged: fix null-pointer dereference due to race Message-ID: <20200724041534.D87eQcPUp%akpm@linux-foundation.org> In-Reply-To: <20200723211432.b31831a0df3bc2cbdae31b40@linux-foundation.org> User-Agent: s-nail v14.8.16 X-Rspamd-Queue-Id: CCB661802BACA X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam04 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: From: "Kirill A. Shutemov" Subject: khugepaged: fix null-pointer dereference due to race 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. Link: http://lkml.kernel.org/r/20200722121439.44328-1-kirill.shutemov@linux.intel.com Fixes: 99cb0dbd47a1 ("mm,thp: add read-only THP support for (non-shmem) FS") Signed-off-by: Kirill A. Shutemov Reported-by: syzbot+ed318e8b790ca72c5ad0@syzkaller.appspotmail.com Reviewed-by: David Hildenbrand Acked-by: Yang Shi Cc: Signed-off-by: Andrew Morton --- mm/khugepaged.c | 3 +++ 1 file changed, 3 insertions(+) --- a/mm/khugepaged.c~khugepaged-fix-null-pointer-dereference-due-to-race +++ a/mm/khugepaged.c @@ -958,6 +958,9 @@ 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; } _