From patchwork Fri Apr 5 06:52:17 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Hou Tao X-Patchwork-Id: 10886959 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 7F8F51669 for ; Fri, 5 Apr 2019 06:48:10 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 5FBE728763 for ; Fri, 5 Apr 2019 06:48:10 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 50AEA287E0; Fri, 5 Apr 2019 06:48:10 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id CAB6728763 for ; Fri, 5 Apr 2019 06:48:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729792AbfDEGsD (ORCPT ); Fri, 5 Apr 2019 02:48:03 -0400 Received: from szxga05-in.huawei.com ([45.249.212.191]:6255 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726389AbfDEGsD (ORCPT ); Fri, 5 Apr 2019 02:48:03 -0400 Received: from DGGEMS407-HUB.china.huawei.com (unknown [172.30.72.60]) by Forcepoint Email with ESMTP id 81B73BF26C006EEB0309; Fri, 5 Apr 2019 14:47:56 +0800 (CST) Received: from huawei.com (10.90.53.225) by DGGEMS407-HUB.china.huawei.com (10.3.19.207) with Microsoft SMTP Server id 14.3.408.0; Fri, 5 Apr 2019 14:47:52 +0800 From: Hou Tao To: , CC: , Subject: [PATCH] sysctl: redefine zero as a unsigned long Date: Fri, 5 Apr 2019 14:52:17 +0800 Message-ID: <20190405065217.125140-1-houtao1@huawei.com> X-Mailer: git-send-email 2.16.2.dirty MIME-Version: 1.0 X-Originating-IP: [10.90.53.225] X-CFilter-Loop: Reflected Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP We have got KASAN splat when tried to set /proc/sys/fs/file-max: BUG: KASAN: global-out-of-bounds in __do_proc_doulongvec_minmax+0x3e4/0x8f0 Read of size 8 at addr ffff20000f9b2980 by task file-max.sh/36819 Call trace: dump_backtrace+0x0/0x3f8 show_stack+0x3c/0x60 dump_stack+0x150/0x1a8 print_address_description+0x2b8/0x5a0 kasan_report+0x278/0x648 __asan_load8+0x124/0x170 __do_proc_doulongvec_minmax+0x3e4/0x8f0 proc_doulongvec_minmax+0x80/0xa0 proc_sys_call_handler+0x188/0x2a0 proc_sys_write+0x5c/0x80 __vfs_write+0x118/0x578 vfs_write+0x184/0x418 ksys_write+0xfc/0x1e8 __arm64_sys_write+0x88/0xa8 el0_svc_common+0x1a4/0x500 el0_svc_handler+0xb8/0x180 el0_svc+0x8/0xc The buggy address belongs to the variable: zero+0x0/0x40 The cause is that proc_doulongvec_minmax() is trying to cast an int pointer (namely &zero) to a unsigned long pointer, and dereferencing it. Although the warning seems does no harm, because zero will be placed in a .bss section, but it's better to kill the KASAN warning by redefining zero as a unsigned long, so it's OK whenever it is accessed as an int or a a unsigned long. An alternative fix seems to be set the minimal value of file-max to be 1, so one_ul can be used instead, but I'm not sure whether or not a file-max with a value of zero has special purpose (e.g., prohibit the file-related activities of all no-privileged users). Signed-off-by: Hou Tao Acked-by: Kees Cook --- kernel/sysctl.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/sysctl.c b/kernel/sysctl.c index e5da394d1ca3..03846e015013 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -124,7 +124,7 @@ static int sixty = 60; static int __maybe_unused neg_one = -1; -static int zero; +static unsigned long zero; static int __maybe_unused one = 1; static int __maybe_unused two = 2; static int __maybe_unused four = 4;