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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 D5D64C2BA19 for ; Wed, 15 Apr 2020 12:01:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AD5E420575 for ; Wed, 15 Apr 2020 12:01:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1586952077; bh=uKXv3sNvVy46P0r1i0/Dj6wNaleBNcC/QD5M1GPVccs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=eji6dasKZXtURUQCFbVoHmrCPYmIrU0qX5LZX1DvOGnhjGc5W/ad//HyTCIa2sm6e DEZpJLOeMfwrCwqQkc2dHvKNs2suBwcx+Clq9kvs+mHkgitD+57vN7gMyzkuDDiBL+ HsSMFE/pc5zP7x+SkmWD5fN3NMvr+lKONjLeF2nc= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S368142AbgDOMBP (ORCPT ); Wed, 15 Apr 2020 08:01:15 -0400 Received: from mail.kernel.org ([198.145.29.99]:43460 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2409411AbgDOLsD (ORCPT ); Wed, 15 Apr 2020 07:48:03 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 764D820775; Wed, 15 Apr 2020 11:48:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1586951283; bh=uKXv3sNvVy46P0r1i0/Dj6wNaleBNcC/QD5M1GPVccs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=R8DUrbXYca/Tof2/KdZzJrHzUsA39OfU4fxv9nGdz0xe/9rzeZAOeIdlAlk5dgo7D M9V/eoqRVUAGBGqqMUZrC8C2lsoBJS/UNA+qDLO8qaadsQMEcd42uK4wZeeXWve5kw AO5MmPsyl6ROibjcQcqVz2u9uGrKvuy9mwcoizrQ= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Qian Cai , Andrew Morton , Marco Elver , Linus Torvalds , Sasha Levin Subject: [PATCH AUTOSEL 4.9 12/21] percpu_counter: fix a data race at vm_committed_as Date: Wed, 15 Apr 2020 07:47:39 -0400 Message-Id: <20200415114748.15713-12-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200415114748.15713-1-sashal@kernel.org> References: <20200415114748.15713-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Qian Cai [ Upstream commit 7e2345200262e4a6056580f0231cccdaffc825f3 ] "vm_committed_as.count" could be accessed concurrently as reported by KCSAN, BUG: KCSAN: data-race in __vm_enough_memory / percpu_counter_add_batch write to 0xffffffff9451c538 of 8 bytes by task 65879 on cpu 35: percpu_counter_add_batch+0x83/0xd0 percpu_counter_add_batch at lib/percpu_counter.c:91 __vm_enough_memory+0xb9/0x260 dup_mm+0x3a4/0x8f0 copy_process+0x2458/0x3240 _do_fork+0xaa/0x9f0 __do_sys_clone+0x125/0x160 __x64_sys_clone+0x70/0x90 do_syscall_64+0x91/0xb05 entry_SYSCALL_64_after_hwframe+0x49/0xbe read to 0xffffffff9451c538 of 8 bytes by task 66773 on cpu 19: __vm_enough_memory+0x199/0x260 percpu_counter_read_positive at include/linux/percpu_counter.h:81 (inlined by) __vm_enough_memory at mm/util.c:839 mmap_region+0x1b2/0xa10 do_mmap+0x45c/0x700 vm_mmap_pgoff+0xc0/0x130 ksys_mmap_pgoff+0x6e/0x300 __x64_sys_mmap+0x33/0x40 do_syscall_64+0x91/0xb05 entry_SYSCALL_64_after_hwframe+0x49/0xbe The read is outside percpu_counter::lock critical section which results in a data race. Fix it by adding a READ_ONCE() in percpu_counter_read_positive() which could also service as the existing compiler memory barrier. Signed-off-by: Qian Cai Signed-off-by: Andrew Morton Acked-by: Marco Elver Link: http://lkml.kernel.org/r/1582302724-2804-1-git-send-email-cai@lca.pw Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin --- include/linux/percpu_counter.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/include/linux/percpu_counter.h b/include/linux/percpu_counter.h index 84a1094496100..b6332cb761a4c 100644 --- a/include/linux/percpu_counter.h +++ b/include/linux/percpu_counter.h @@ -76,9 +76,9 @@ static inline s64 percpu_counter_read(struct percpu_counter *fbc) */ static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc) { - s64 ret = fbc->count; + /* Prevent reloads of fbc->count */ + s64 ret = READ_ONCE(fbc->count); - barrier(); /* Prevent reloads of fbc->count */ if (ret >= 0) return ret; return 0; -- 2.20.1