From nobody Wed Apr 8 22:51:22 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 069BDC38A02 for ; Mon, 31 Oct 2022 11:39:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230409AbiJaLjy (ORCPT ); Mon, 31 Oct 2022 07:39:54 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38622 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230443AbiJaLjt (ORCPT ); Mon, 31 Oct 2022 07:39:49 -0400 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A3F97E0E8 for ; Mon, 31 Oct 2022 04:39:44 -0700 (PDT) Received: from kwepemi500012.china.huawei.com (unknown [172.30.72.54]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4N19zr1SkPzVj05; Mon, 31 Oct 2022 19:34:48 +0800 (CST) Received: from cgs.huawei.com (10.244.148.83) by kwepemi500012.china.huawei.com (7.221.188.12) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.31; Mon, 31 Oct 2022 19:39:42 +0800 From: Gaosheng Cui To: , , CC: Subject: [PATCH] mount: fix undefined behavior in bit shift for MS_NOUSER Date: Mon, 31 Oct 2022 19:39:42 +0800 Message-ID: <20221031113942.4183728-1-cuigaosheng1@huawei.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Originating-IP: [10.244.148.83] X-ClientProxiedBy: dggems704-chm.china.huawei.com (10.3.19.181) To kwepemi500012.china.huawei.com (7.221.188.12) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Shifting signed 32-bit value by 31 bits is undefined, so changing significant bit to unsigned. The UBSAN warning calltrace like below: UBSAN: shift-out-of-bounds in fs/namespace.c:3309:14 left shift of 1 by 31 places cannot be represented in type 'int' Call Trace: dump_stack_lvl+0x7d/0xa5 dump_stack+0x15/0x1b ubsan_epilogue+0xe/0x4e __ubsan_handle_shift_out_of_bounds+0x1e7/0x20c path_mount+0x93/0xd50 init_mount+0x6a/0xa3 devtmpfs_setup+0x47/0x7e devtmpfsd+0x1a/0x50 kthread+0x126/0x160 ret_from_fork+0x1f/0x30 Fixes: e262e32d6bde ("vfs: Suppress MS_* flag defs within the kernel unless= explicitly enabled") Signed-off-by: Gaosheng Cui --- include/uapi/linux/mount.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/uapi/linux/mount.h b/include/uapi/linux/mount.h index 4d93967f8aea..035de4bd968f 100644 --- a/include/uapi/linux/mount.h +++ b/include/uapi/linux/mount.h @@ -44,7 +44,7 @@ #define MS_NOSEC (1<<28) #define MS_BORN (1<<29) #define MS_ACTIVE (1<<30) -#define MS_NOUSER (1<<31) +#define MS_NOUSER (1U<<31) =20 /* * Superblock flags that can be altered by MS_REMOUNT --=20 2.25.1