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=-9.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,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 1B159C352A5 for ; Mon, 10 Feb 2020 17:00:47 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id D3F8120842 for ; Mon, 10 Feb 2020 17:00:46 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lca.pw header.i=@lca.pw header.b="P71NqZwm" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D3F8120842 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lca.pw Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 633626B0130; Mon, 10 Feb 2020 12:00:46 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 5E5586B0131; Mon, 10 Feb 2020 12:00:46 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4D2BE6B0132; Mon, 10 Feb 2020 12:00:46 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0081.hostedemail.com [216.40.44.81]) by kanga.kvack.org (Postfix) with ESMTP id 3038B6B0130 for ; Mon, 10 Feb 2020 12:00:46 -0500 (EST) Received: from smtpin15.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id DD797180AD804 for ; Mon, 10 Feb 2020 17:00:45 +0000 (UTC) X-FDA: 76474831650.15.dolls77_69b488cc1b16 X-HE-Tag: dolls77_69b488cc1b16 X-Filterd-Recvd-Size: 5424 Received: from mail-qv1-f67.google.com (mail-qv1-f67.google.com [209.85.219.67]) by imf35.hostedemail.com (Postfix) with ESMTP for ; Mon, 10 Feb 2020 17:00:45 +0000 (UTC) Received: by mail-qv1-f67.google.com with SMTP id dp13so3484030qvb.7 for ; Mon, 10 Feb 2020 09:00:45 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=lca.pw; s=google; h=from:to:cc:subject:date:message-id; bh=tDzjX5yb/FnpEzDqhJGtzVk0lEjmLNCz+7d6psCMd5o=; b=P71NqZwmSzuCdzx2tb34ueZZ/UqgiDtVWNB9ymBVjnvu0WwfyP99JP8UEOhnrJQ6Uq AOdQA1v5UyaVgjwPWJNL7cA07ZglpPk201Zci7I6Cjxqf140+sMOSEMAqy9pyhtUM8ch rzlhO1ty/E8koJ79hoEN/wlRQgHlDyCHwQpvpY4sySfZe7I5V4kY6iTFmhpNrhyA1Z/6 Cd4qWBDDtcY+VfHybe8XbOwRNn2aFNwXS+I2E3PmbrqhTTDUIJyRqfsVMy60XtATzt5o 2s3Fe5EIAxZ9k6Qq/IFyQO/UhkqAoHGeybQ9cdKgPGSP3edtrYQ3MUWJAP2RnyGjdlGI 05Nw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id; bh=tDzjX5yb/FnpEzDqhJGtzVk0lEjmLNCz+7d6psCMd5o=; b=gPbeBBB09xJaYglMDEA9ob37qx2V7omMHygZgJr07DjLWW1N405JxHkbU6F78dm3HL VU6lMCE8ASgGa+aRhfMpIw8a83TBZlNjZUNzH378jC+YNeDX+pSCQc3DJAmuRAf11eFJ LYkUZ+VGdlvPcnpvM/ydeWGeoYNoRTaP7bCo6ZbVdWYApuSJ6k22CB8Fm8leSXYTRb7p XYbV86x9NqoMWGlcf+eBIyyunbScFlHJVZ3zh4Tg+JADJfixR/m8QqNFBGQOzR+q2cVh Jl3vu48JJGv396WgYu7mUo5zKQfzBjPF7oPzAwHFuzkRpL/dJR3LxlZpR6n1iTvHqY3g xn2w== X-Gm-Message-State: APjAAAVL5PBf6tXmLj8uLgSXTFk0uLTQAEtLFpDcWVMA6V27zJH5UxcD RV1+WOgy7QD8NJqJ/pgKzRdOeQ== X-Google-Smtp-Source: APXvYqzSX3FsN7O6e1AgBOQKWgbQ+6aGfCZV35s07hH/ofSVdWBOXPQ9wgQk8v33u160/lAvyaqwpw== X-Received: by 2002:a05:6214:1267:: with SMTP id r7mr10932258qvv.160.1581354044600; Mon, 10 Feb 2020 09:00:44 -0800 (PST) Received: from qcai.nay.com (nat-pool-bos-t.redhat.com. [66.187.233.206]) by smtp.gmail.com with ESMTPSA id r1sm442348qtu.83.2020.02.10.09.00.42 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 10 Feb 2020 09:00:43 -0800 (PST) From: Qian Cai To: akpm@linux-foundation.org Cc: elver@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Qian Cai Subject: [PATCH -next] mm/filemap: fix a data race in filemap_fault() Date: Mon, 10 Feb 2020 12:00:29 -0500 Message-Id: <1581354029-20154-1-git-send-email-cai@lca.pw> X-Mailer: git-send-email 1.8.3.1 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: struct file_ra_state ra.mmap_miss could be accessed concurrently during page faults as noticed by KCSAN, BUG: KCSAN: data-race in filemap_fault / filemap_map_pages write to 0xffff9b1700a2c1b4 of 4 bytes by task 3292 on cpu 30: filemap_fault+0x920/0xfc0 do_sync_mmap_readahead at mm/filemap.c:2384 (inlined by) filemap_fault at mm/filemap.c:2486 __xfs_filemap_fault+0x112/0x3e0 [xfs] xfs_filemap_fault+0x74/0x90 [xfs] __do_fault+0x9e/0x220 do_fault+0x4a0/0x920 __handle_mm_fault+0xc69/0xd00 handle_mm_fault+0xfc/0x2f0 do_page_fault+0x263/0x6f9 page_fault+0x34/0x40 read to 0xffff9b1700a2c1b4 of 4 bytes by task 3313 on cpu 32: filemap_map_pages+0xc2e/0xd80 filemap_map_pages at mm/filemap.c:2625 do_fault+0x3da/0x920 __handle_mm_fault+0xc69/0xd00 handle_mm_fault+0xfc/0x2f0 do_page_fault+0x263/0x6f9 page_fault+0x34/0x40 Reported by Kernel Concurrency Sanitizer on: CPU: 32 PID: 3313 Comm: systemd-udevd Tainted: G W L 5.5.0-next-20200210+ #1 Hardware name: HPE ProLiant DL385 Gen10/ProLiant DL385 Gen10, BIOS A40 07/10/2019 ra.mmap_miss is used to contribute the readahead decisions, a data race could be undesirable. Since the stores are aligned and less than word-size, assume they are safe. Thus, fixing it by adding READ_ONCE() for the loads except those places comparing to zero where they are safe. Signed-off-by: Qian Cai --- mm/filemap.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/mm/filemap.c b/mm/filemap.c index 1784478270e1..b6c1d37f7ea3 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2380,14 +2380,14 @@ static struct file *do_sync_mmap_readahead(struct vm_fault *vmf) } /* Avoid banging the cache line if not needed */ - if (ra->mmap_miss < MMAP_LOTSAMISS * 10) + if (READ_ONCE(ra->mmap_miss) < MMAP_LOTSAMISS * 10) ra->mmap_miss++; /* * Do we miss much more than hit in this file? If so, * stop bothering with read-ahead. It will only hurt. */ - if (ra->mmap_miss > MMAP_LOTSAMISS) + if (READ_ONCE(ra->mmap_miss) > MMAP_LOTSAMISS) return fpin; /* @@ -2418,7 +2418,7 @@ static struct file *do_async_mmap_readahead(struct vm_fault *vmf, /* If we don't want any read-ahead, don't bother */ if (vmf->vma->vm_flags & VM_RAND_READ) return fpin; - if (ra->mmap_miss > 0) + if (data_race(ra->mmap_miss > 0)) ra->mmap_miss--; if (PageReadahead(page)) { fpin = maybe_unlock_mmap_for_io(vmf, fpin); @@ -2622,7 +2622,7 @@ void filemap_map_pages(struct vm_fault *vmf, if (page->index >= max_idx) goto unlock; - if (file->f_ra.mmap_miss > 0) + if (data_race(file->f_ra.mmap_miss > 0)) file->f_ra.mmap_miss--; vmf->address += (xas.xa_index - last_pgoff) << PAGE_SHIFT; -- 1.8.3.1