From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-it0-f71.google.com (mail-it0-f71.google.com [209.85.214.71]) by kanga.kvack.org (Postfix) with ESMTP id 3486C6B0335 for ; Thu, 17 Nov 2016 12:14:19 -0500 (EST) Received: by mail-it0-f71.google.com with SMTP id o1so124889283ito.7 for ; Thu, 17 Nov 2016 09:14:19 -0800 (PST) Received: from out03.mta.xmission.com (out03.mta.xmission.com. [166.70.13.233]) by mx.google.com with ESMTPS id a75si3026570ioe.90.2016.11.17.09.14.18 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 17 Nov 2016 09:14:18 -0800 (PST) From: ebiederm@xmission.com (Eric W. Biederman) References: <87twcbq696.fsf@x220.int.ebiederm.org> <20161018135031.GB13117@dhcp22.suse.cz> <8737jt903u.fsf@xmission.com> <20161018150507.GP14666@pc.thejh.net> <87twc9656s.fsf@xmission.com> <20161018191206.GA1210@laptop.thejh.net> <87r37dnz74.fsf@xmission.com> <87k2d5nytz.fsf_-_@xmission.com> <87y41kjn6l.fsf@xmission.com> <20161019172917.GE1210@laptop.thejh.net> <87pomwi5p2.fsf@xmission.com> <87pomwghda.fsf@xmission.com> <87twb6avk8.fsf_-_@xmission.com> Date: Thu, 17 Nov 2016 11:10:13 -0600 In-Reply-To: <87twb6avk8.fsf_-_@xmission.com> (Eric W. Biederman's message of "Thu, 17 Nov 2016 11:02:47 -0600") Message-ID: <87d1huav7u.fsf_-_@xmission.com> MIME-Version: 1.0 Content-Type: text/plain Subject: [REVIEW][PATCH 3/3] exec: Ensure mm->user_ns contains the execed files Sender: owner-linux-mm@kvack.org List-ID: To: Linux Containers Cc: Oleg Nesterov , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , Linux FS Devel , Michal Hocko , Jann Horn , Willy Tarreau , Kees Cook , Andy Lutomirski When the user namespace support was merged the need to prevent ptrace from revealing the contents of an unreadable executable was overlooked. Correct this oversight by ensuring that the executed file or files are in mm->user_ns, by adjusting mm->user_ns. Use the new function privileged_wrt_inode_uidgid to see if the executable is a member of the user namespace, and as such if having CAP_SYS_PTRACE in the user namespace should allow tracing the executable. If not update mm->user_ns to the parent user namespace until an appropriate parent is found. Cc: stable@vger.kernel.org Reported-by: Jann Horn Fixes: 9e4a36ece652 ("userns: Fail exec for suid and sgid binaries with ids outside our user namespace.") Signed-off-by: "Eric W. Biederman" --- fs/exec.c | 16 +++++++++++++++- include/linux/capability.h | 1 + kernel/capability.c | 16 ++++++++++++++-- 3 files changed, 30 insertions(+), 3 deletions(-) diff --git a/fs/exec.c b/fs/exec.c index de107f74e055..4ce5d68d6f5b 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1275,8 +1275,22 @@ EXPORT_SYMBOL(flush_old_exec); void would_dump(struct linux_binprm *bprm, struct file *file) { - if (inode_permission(file_inode(file), MAY_READ) < 0) + struct inode *inode = file_inode(file); + if (inode_permission(inode, MAY_READ) < 0) { + struct user_namespace *old, *user_ns; bprm->interp_flags |= BINPRM_FLAGS_ENFORCE_NONDUMP; + + /* Ensure mm->user_ns contains the executable */ + user_ns = old = bprm->mm->user_ns; + while ((user_ns != &init_user_ns) && + !privileged_wrt_inode_uidgid(user_ns, inode)) + user_ns = user_ns->parent; + + if (old != user_ns) { + bprm->mm->user_ns = get_user_ns(user_ns); + put_user_ns(old); + } + } } EXPORT_SYMBOL(would_dump); diff --git a/include/linux/capability.h b/include/linux/capability.h index d6088e2a7668..6ffb67e10c06 100644 --- a/include/linux/capability.h +++ b/include/linux/capability.h @@ -240,6 +240,7 @@ static inline bool ns_capable_noaudit(struct user_namespace *ns, int cap) return true; } #endif /* CONFIG_MULTIUSER */ +extern bool privileged_wrt_inode_uidgid(struct user_namespace *ns, const struct inode *inode); extern bool capable_wrt_inode_uidgid(const struct inode *inode, int cap); extern bool file_ns_capable(const struct file *file, struct user_namespace *ns, int cap); extern bool ptracer_capable(struct task_struct *tsk, struct user_namespace *ns); diff --git a/kernel/capability.c b/kernel/capability.c index dfa0e4528b0b..4984e1f552eb 100644 --- a/kernel/capability.c +++ b/kernel/capability.c @@ -457,6 +457,19 @@ bool file_ns_capable(const struct file *file, struct user_namespace *ns, EXPORT_SYMBOL(file_ns_capable); /** + * privileged_wrt_inode_uidgid - Do capabilities in the namespace work over the inode? + * @ns: The user namespace in question + * @inode: The inode in question + * + * Return true if the inode uid and gid are within the namespace. + */ +bool privileged_wrt_inode_uidgid(struct user_namespace *ns, const struct inode *inode) +{ + return kuid_has_mapping(ns, inode->i_uid) && + kgid_has_mapping(ns, inode->i_gid); +} + +/** * capable_wrt_inode_uidgid - Check nsown_capable and uid and gid mapped * @inode: The inode in question * @cap: The capability in question @@ -469,8 +482,7 @@ bool capable_wrt_inode_uidgid(const struct inode *inode, int cap) { struct user_namespace *ns = current_user_ns(); - return ns_capable(ns, cap) && kuid_has_mapping(ns, inode->i_uid) && - kgid_has_mapping(ns, inode->i_gid); + return ns_capable(ns, cap) && privileged_wrt_inode_uidgid(ns, inode); } EXPORT_SYMBOL(capable_wrt_inode_uidgid); -- 2.10.1 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org