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=ham 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 458DEC2BA19 for ; Wed, 15 Apr 2020 13:04:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 217872064A for ; Wed, 15 Apr 2020 13:04:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1586955863; bh=8Zkwt3Nxc5a6mdUgf20I8irYrlccMGLwx42I/QawL/4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=OA5U4P7+APEYu4r0aj4rP9du0TQfFRNULtFgl9MxVWNk6f7XdAwJLCD5cfLCCh2zW KzHe+sYB6iz2GFcrt8Uf2z8DjD7JcMz88LikbSgl0SAfIIQhPDzZElfojN1yj1MNFZ pFq3RbE7KCwcuOtXvbYgec25M8m6Qpj1n5i1coao= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2505848AbgDONEU (ORCPT ); Wed, 15 Apr 2020 09:04:20 -0400 Received: from mail.kernel.org ([198.145.29.99]:54800 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2897137AbgDOLg0 (ORCPT ); Wed, 15 Apr 2020 07:36:26 -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 6D5C8214D8; Wed, 15 Apr 2020 11:36:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1586950580; bh=8Zkwt3Nxc5a6mdUgf20I8irYrlccMGLwx42I/QawL/4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=retB1e2Kycd123sySla2MnFKGUfESh9xdhLr7BJN0IB9knB6QlCs2H3HAPBP4fBfH qj1tvQld0j8J6Ba6F03y1QoxPCV6pBP4gssr6krTQpnz74xaLDI7pndDxICluPymYJ Fvf3ZkyhsV/0uq7e8/sI2H/2ey8ZePIh5N+SbxUg= 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 5.6 080/129] percpu_counter: fix a data race at vm_committed_as Date: Wed, 15 Apr 2020 07:33:55 -0400 Message-Id: <20200415113445.11881-80-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200415113445.11881-1-sashal@kernel.org> References: <20200415113445.11881-1-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 4f052496cdfd7..0a4f54dd4737b 100644 --- a/include/linux/percpu_counter.h +++ b/include/linux/percpu_counter.h @@ -78,9 +78,9 @@ 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