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=-3.8 required=3.0 tests=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 953F2C43331 for ; Thu, 2 Apr 2020 04:06:16 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 58069206E9 for ; Thu, 2 Apr 2020 04:06:16 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="al+D/nkA" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 58069206E9 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 097548E0037; Thu, 2 Apr 2020 00:06:16 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 048048E000D; Thu, 2 Apr 2020 00:06:16 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id EC7188E0037; Thu, 2 Apr 2020 00:06:15 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0254.hostedemail.com [216.40.44.254]) by kanga.kvack.org (Postfix) with ESMTP id CF6B88E000D for ; Thu, 2 Apr 2020 00:06:15 -0400 (EDT) Received: from smtpin16.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 999518248047 for ; Thu, 2 Apr 2020 04:06:15 +0000 (UTC) X-FDA: 76661577510.16.sock66_369cfe5e35e14 X-HE-Tag: sock66_369cfe5e35e14 X-Filterd-Recvd-Size: 3997 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf47.hostedemail.com (Postfix) with ESMTP for ; Thu, 2 Apr 2020 04:06:15 +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 42B1820747; Thu, 2 Apr 2020 04:06:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1585800374; bh=sjwCUvlh9gZKAWj5bGEL0t9cbng3hEJLn6D/RFUwhyQ=; h=Date:From:To:Subject:In-Reply-To:From; b=al+D/nkARFksVV1LtHTjpWPwMeiywe8AQxAiAKbmYNLyAky08vEFquN7LlcMqF4lf C88EOf9rsU8+Fvn5ucVR5xrtCd37JtPs91XVBycPALPJo9uuiuJjDKjXSyYEjSlwzD fwfsk1cPxuzrEGpE1XpYiy60NRzUx6Jqnke2jJx0= Date: Wed, 01 Apr 2020 21:06:13 -0700 From: Andrew Morton To: akpm@linux-foundation.org, cai@lca.pw, elver@google.com, hughd@google.com, linux-mm@kvack.org, mm-commits@vger.kernel.org, torvalds@linux-foundation.org Subject: [patch 055/155] mm/swapfile: fix data races in try_to_unuse() Message-ID: <20200402040613.A8knyzgJ0%akpm@linux-foundation.org> In-Reply-To: <20200401210155.09e3b9742e1c6e732f5a7250@linux-foundation.org> User-Agent: s-nail v14.8.16 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: Qian Cai Subject: mm/swapfile: fix data races in try_to_unuse() si->inuse_pages could be accessed concurrently as noticed by KCSAN, write to 0xffff98b00ebd04dc of 4 bytes by task 82262 on cpu 92: swap_range_free+0xbe/0x230 swap_range_free at mm/swapfile.c:719 swapcache_free_entries+0x1be/0x250 free_swap_slot+0x1c8/0x220 __swap_entry_free.constprop.19+0xa3/0xb0 free_swap_and_cache+0x53/0xa0 unmap_page_range+0x7e0/0x1ce0 unmap_single_vma+0xcd/0x170 unmap_vmas+0x18b/0x220 exit_mmap+0xee/0x220 mmput+0xe7/0x240 do_exit+0x598/0xfd0 do_group_exit+0x8b/0x180 get_signal+0x293/0x13d0 do_signal+0x37/0x5d0 prepare_exit_to_usermode+0x1b7/0x2c0 ret_from_intr+0x32/0x42 read to 0xffff98b00ebd04dc of 4 bytes by task 82499 on cpu 46: try_to_unuse+0x86b/0xc80 try_to_unuse at mm/swapfile.c:2185 __x64_sys_swapoff+0x372/0xd40 do_syscall_64+0x91/0xb05 entry_SYSCALL_64_after_hwframe+0x49/0xbe The plain reads in try_to_unuse() are outside si->lock critical section which result in data races that could be dangerous to be used in a loop. Fix them by adding READ_ONCE(). Link: http://lkml.kernel.org/r/1582578903-29294-1-git-send-email-cai@lca.pw Signed-off-by: Qian Cai Reviewed-by: Andrew Morton Cc: Marco Elver Cc: Hugh Dickins Signed-off-by: Andrew Morton --- mm/swapfile.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) --- a/mm/swapfile.c~mm-swapfile-fix-data-races-in-try_to_unuse +++ a/mm/swapfile.c @@ -2132,7 +2132,7 @@ int try_to_unuse(unsigned int type, bool swp_entry_t entry; unsigned int i; - if (!si->inuse_pages) + if (!READ_ONCE(si->inuse_pages)) return 0; if (!frontswap) @@ -2148,7 +2148,7 @@ retry: spin_lock(&mmlist_lock); p = &init_mm.mmlist; - while (si->inuse_pages && + while (READ_ONCE(si->inuse_pages) && !signal_pending(current) && (p = p->next) != &init_mm.mmlist) { @@ -2177,7 +2177,7 @@ retry: mmput(prev_mm); i = 0; - while (si->inuse_pages && + while (READ_ONCE(si->inuse_pages) && !signal_pending(current) && (i = find_next_to_unuse(si, i, frontswap)) != 0) { @@ -2219,7 +2219,7 @@ retry: * been preempted after get_swap_page(), temporarily hiding that swap. * It's easy and robust (though cpu-intensive) just to keep retrying. */ - if (si->inuse_pages) { + if (READ_ONCE(si->inuse_pages)) { if (!signal_pending(current)) goto retry; retval = -EINTR; _