From patchwork Fri Sep 6 15:24:52 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Micka=C3=ABl_Sala=C3=BCn?= X-Patchwork-Id: 11135555 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id A5F0015E6 for ; Fri, 6 Sep 2019 15:26:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8F0BD2186A for ; Fri, 6 Sep 2019 15:26:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2405708AbfIFP0n (ORCPT ); Fri, 6 Sep 2019 11:26:43 -0400 Received: from smtp-sh2.infomaniak.ch ([128.65.195.6]:53743 "EHLO smtp-sh2.infomaniak.ch" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2404161AbfIFP0i (ORCPT ); Fri, 6 Sep 2019 11:26:38 -0400 Received: from smtp5.infomaniak.ch (smtp5.infomaniak.ch [83.166.132.18]) by smtp-sh2.infomaniak.ch (8.14.4/8.14.4/Debian-8+deb8u2) with ESMTP id x86FP5ah085900 (version=TLSv1/SSLv3 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 6 Sep 2019 17:25:05 +0200 Received: from localhost (ns3096276.ip-94-23-54.eu [94.23.54.103]) (authenticated bits=0) by smtp5.infomaniak.ch (8.14.5/8.14.5) with ESMTP id x86FP4Cs047634; Fri, 6 Sep 2019 17:25:04 +0200 From: =?utf-8?q?Micka=C3=ABl_Sala=C3=BCn?= To: linux-kernel@vger.kernel.org Cc: =?utf-8?q?Micka=C3=ABl_Sala=C3=BCn?= , Aleksa Sarai , Alexei Starovoitov , Al Viro , Andy Lutomirski , Christian Heimes , Daniel Borkmann , Eric Chiang , Florian Weimer , James Morris , Jan Kara , Jann Horn , Jonathan Corbet , Kees Cook , Matthew Garrett , Matthew Wilcox , Michael Kerrisk , =?utf-8?q?Micka=C3=ABl_Sala=C3=BC?= =?utf-8?q?n?= , Mimi Zohar , =?utf-8?q?Philippe_Tr=C3=A9buchet?= , Scott Shell , Sean Christopherson , Shuah Khan , Song Liu , Steve Dower , Steve Grubb , Thibaut Sautereau , Vincent Strubel , Yves-Alexis Perez , kernel-hardening@lists.openwall.com, linux-api@vger.kernel.org, linux-security-module@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: [PATCH v2 2/5] fs: Add a MAY_EXECMOUNT flag to infer the noexec mount propertie Date: Fri, 6 Sep 2019 17:24:52 +0200 Message-Id: <20190906152455.22757-3-mic@digikod.net> X-Mailer: git-send-email 2.23.0.rc1 In-Reply-To: <20190906152455.22757-1-mic@digikod.net> References: <20190906152455.22757-1-mic@digikod.net> MIME-Version: 1.0 X-Antivirus: Dr.Web (R) for Unix mail servers drweb plugin ver.6.0.2.8 X-Antivirus-Code: 0x100000 Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: An LSM doesn't get path information related to an access request to open an inode. This new (internal) MAY_EXECMOUNT flag enables an LSM to check if the underlying mount point of an inode is marked as executable. This is useful to implement a security policy taking advantage of the noexec mount option. This flag is set according to path_noexec(), which checks if a mount point is mounted with MNT_NOEXEC or if the underlying superblock is SB_I_NOEXEC. Signed-off-by: Mickaël Salaün Reviewed-by: Philippe Trébuchet Reviewed-by: Thibaut Sautereau Cc: Al Viro Cc: Kees Cook Cc: Mickaël Salaün --- fs/namei.c | 2 ++ include/linux/fs.h | 2 ++ 2 files changed, 4 insertions(+) diff --git a/fs/namei.c b/fs/namei.c index 209c51a5226c..0a6b9483d0cb 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -2968,6 +2968,8 @@ static int may_open(const struct path *path, int acc_mode, int flag) break; } + /* Pass the mount point executability. */ + acc_mode |= path_noexec(path) ? 0 : MAY_EXECMOUNT; error = inode_permission(inode, MAY_OPEN | acc_mode); if (error) return error; diff --git a/include/linux/fs.h b/include/linux/fs.h index 848f5711bdf0..e57609dac8dd 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -101,6 +101,8 @@ typedef int (dio_iodone_t)(struct kiocb *iocb, loff_t offset, #define MAY_NOT_BLOCK 0x00000080 /* the inode is opened with O_MAYEXEC */ #define MAY_OPENEXEC 0x00000100 +/* the mount point is marked as executable */ +#define MAY_EXECMOUNT 0x00000200 /* * flags in file.f_mode. Note that FMODE_READ and FMODE_WRITE must correspond