From patchwork Sun Nov 15 10:37:07 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christian Brauner X-Patchwork-Id: 11906247 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 0ADB5138B for ; Sun, 15 Nov 2020 10:48:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F070F2417E for ; Sun, 15 Nov 2020 10:48:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727065AbgKOKr7 (ORCPT ); Sun, 15 Nov 2020 05:47:59 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:59758 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726647AbgKOKrS (ORCPT ); Sun, 15 Nov 2020 05:47:18 -0500 Received: from ip5f5af0a0.dynamic.kabel-deutschland.de ([95.90.240.160] helo=wittgenstein.fritz.box) by youngberry.canonical.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.86_2) (envelope-from ) id 1keFRc-0000Kt-PM; Sun, 15 Nov 2020 10:39:40 +0000 From: Christian Brauner To: Alexander Viro , Christoph Hellwig , linux-fsdevel@vger.kernel.org Cc: John Johansen , James Morris , Mimi Zohar , Dmitry Kasatkin , Stephen Smalley , Casey Schaufler , Arnd Bergmann , Andreas Dilger , OGAWA Hirofumi , Geoffrey Thomas , Mrunal Patel , Josh Triplett , Andy Lutomirski , Theodore Tso , Alban Crequy , Tycho Andersen , David Howells , James Bottomley , Jann Horn , Seth Forshee , =?utf-8?q?St=C3=A9phane_Graber?= , Aleksa Sarai , Lennart Poettering , "Eric W. Biederman" , smbarber@chromium.org, Phil Estes , Serge Hallyn , Kees Cook , Todd Kjos , Jonathan Corbet , containers@lists.linux-foundation.org, linux-security-module@vger.kernel.org, linux-api@vger.kernel.org, linux-ext4@vger.kernel.org, linux-audit@redhat.com, linux-integrity@vger.kernel.org, selinux@vger.kernel.org, Christian Brauner , Christoph Hellwig Subject: [PATCH v2 28/39] exec: handle idmapped mounts Date: Sun, 15 Nov 2020 11:37:07 +0100 Message-Id: <20201115103718.298186-29-christian.brauner@ubuntu.com> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20201115103718.298186-1-christian.brauner@ubuntu.com> References: <20201115103718.298186-1-christian.brauner@ubuntu.com> MIME-Version: 1.0 Precedence: bulk List-ID: When executing a setuid binary the kernel will verify in bprm_fill_uid() that the inode has a mapping in the caller's user namespace before setting the callers uid and gid. Let bprm_fill_uid() handle idmapped mounts. If the inode is accessed through an idmapped mount it is mapped according to the mount's user namespace. Afterwards the checks are identical to non-idmapped mounts.On regular mounts this is a nop. Cc: Christoph Hellwig Cc: David Howells Cc: Al Viro Cc: linux-fsdevel@vger.kernel.org Signed-off-by: Christian Brauner --- /* v2 */ unchanged --- fs/exec.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/fs/exec.c b/fs/exec.c index 10c06fdf78a7..7d6d3dd17e84 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1567,6 +1567,7 @@ static void check_unsafe_exec(struct linux_binprm *bprm) static void bprm_fill_uid(struct linux_binprm *bprm, struct file *file) { /* Handle suid and sgid on files */ + struct user_namespace *user_ns; struct inode *inode; unsigned int mode; kuid_t uid; @@ -1583,13 +1584,15 @@ static void bprm_fill_uid(struct linux_binprm *bprm, struct file *file) if (!(mode & (S_ISUID|S_ISGID))) return; + user_ns = mnt_user_ns(file->f_path.mnt); + /* Be careful if suid/sgid is set */ inode_lock(inode); /* reload atomically mode/uid/gid now that lock held */ mode = inode->i_mode; - uid = inode->i_uid; - gid = inode->i_gid; + uid = i_uid_into_mnt(user_ns, inode); + gid = i_gid_into_mnt(user_ns, inode); inode_unlock(inode); /* We ignore suid/sgid if there are no mappings for them in the ns */