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 00E02C433ED for ; Fri, 24 Jul 2020 04:15:15 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id B9B79207DF for ; Fri, 24 Jul 2020 04:15:14 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="kByVLPuQ" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B9B79207DF 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 638F28D0005; Fri, 24 Jul 2020 00:15:14 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 60F2A6B0025; Fri, 24 Jul 2020 00:15:14 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4FE658D0005; Fri, 24 Jul 2020 00:15:14 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0072.hostedemail.com [216.40.44.72]) by kanga.kvack.org (Postfix) with ESMTP id 3A29C6B0024 for ; Fri, 24 Jul 2020 00:15:14 -0400 (EDT) Received: from smtpin06.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id EC0518248047 for ; Fri, 24 Jul 2020 04:15:13 +0000 (UTC) X-FDA: 77071654506.06.clock97_5f15a9f26f44 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin06.hostedemail.com (Postfix) with ESMTP id BFF401004F23D for ; Fri, 24 Jul 2020 04:15:13 +0000 (UTC) X-HE-Tag: clock97_5f15a9f26f44 X-Filterd-Recvd-Size: 4224 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf37.hostedemail.com (Postfix) with ESMTP for ; Fri, 24 Jul 2020 04:15:13 +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 E489C22B40; Fri, 24 Jul 2020 04:15:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1595564112; bh=NjpN63dLldgRvU6Vkn9HoaV4XH4SpKKCqrhcQBIE61Q=; h=Date:From:To:Subject:In-Reply-To:From; b=kByVLPuQnV+PjQVuKy0rIJ+fxjFdCR2RSlmhoYStbmc5LwkyRs70n8XiWQdjd3VLO nOH0VrrLyQLp9PQrP7DtenStzX7S4fAAQkBJzuKtCxWn5KPX/cbibtrRa30VPJ+se6 lRd9TdpNFPnRHGxAFDlU1I4gIabSBZzOm8uJUVvQ= Date: Thu, 23 Jul 2020 21:15:11 -0700 From: Andrew Morton To: akpm@linux-foundation.org, jannh@google.com, kirill.shutemov@linux.intel.com, linux-mm@kvack.org, mm-commits@vger.kernel.org, oleg@redhat.com, stable@vger.kernel.org, torvalds@linux-foundation.org, vbabka@suse.cz, willy@infradead.org, yang.shi@linux.alibaba.com Subject: [patch 02/15] mm/mmap.c: close race between munmap() and expand_upwards()/downwards() Message-ID: <20200724041511.gcyDW6Qmq%akpm@linux-foundation.org> In-Reply-To: <20200723211432.b31831a0df3bc2cbdae31b40@linux-foundation.org> User-Agent: s-nail v14.8.16 X-Rspamd-Queue-Id: BFF401004F23D 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: mm/mmap.c: close race between munmap() and expand_upwards()/downwards() VMA with VM_GROWSDOWN or VM_GROWSUP flag set can change their size under mmap_read_lock(). It can lead to race with __do_munmap(): Thread A Thread B __do_munmap() detach_vmas_to_be_unmapped() mmap_write_downgrade() expand_downwards() vma->vm_start = address; // The VMA now overlaps with // VMAs detached by the Thread A // page fault populates expanded part // of the VMA unmap_region() // Zaps pagetables partly // populated by Thread B Similar race exists for expand_upwards(). The fix is to avoid downgrading mmap_lock in __do_munmap() if detached VMAs are next to VM_GROWSDOWN or VM_GROWSUP VMA. [akpm@linux-foundation.org: s/mmap_sem/mmap_lock/ in comment] Link: http://lkml.kernel.org/r/20200709105309.42495-1-kirill.shutemov@linux.intel.com Fixes: dd2283f2605e ("mm: mmap: zap pages with read mmap_sem in munmap") Signed-off-by: Kirill A. Shutemov Reported-by: Jann Horn Acked-by: Vlastimil Babka Reviewed-by: Yang Shi Cc: Oleg Nesterov Cc: Matthew Wilcox Cc: [4.20+] Signed-off-by: Andrew Morton --- mm/mmap.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) --- a/mm/mmap.c~mm-close-race-between-munmap-and-expand_upwards-downwards +++ a/mm/mmap.c @@ -2620,7 +2620,7 @@ static void unmap_region(struct mm_struc * Create a list of vma's touched by the unmap, removing them from the mm's * vma list as we go.. */ -static void +static bool detach_vmas_to_be_unmapped(struct mm_struct *mm, struct vm_area_struct *vma, struct vm_area_struct *prev, unsigned long end) { @@ -2645,6 +2645,17 @@ detach_vmas_to_be_unmapped(struct mm_str /* Kill the cache */ vmacache_invalidate(mm); + + /* + * Do not downgrade mmap_lock if we are next to VM_GROWSDOWN or + * VM_GROWSUP VMA. Such VMAs can change their size under + * down_read(mmap_lock) and collide with the VMA we are about to unmap. + */ + if (vma && (vma->vm_flags & VM_GROWSDOWN)) + return false; + if (prev && (prev->vm_flags & VM_GROWSUP)) + return false; + return true; } /* @@ -2825,7 +2836,8 @@ int __do_munmap(struct mm_struct *mm, un } /* Detach vmas from rbtree */ - detach_vmas_to_be_unmapped(mm, vma, prev, end); + if (!detach_vmas_to_be_unmapped(mm, vma, prev, end)) + downgrade = false; if (downgrade) mmap_write_downgrade(mm); _