lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Wed, 18 Nov 2015 11:00:53 +1100 (AEDT) From: James Morris <jmorris@...ei.org> To: Seth Forshee <seth.forshee@...onical.com> cc: "Eric W. Biederman" <ebiederm@...ssion.com>, Alexander Viro <viro@...iv.linux.org.uk>, Serge Hallyn <serge.hallyn@...onical.com>, James Morris <james.l.morris@...cle.com>, "Serge E. Hallyn" <serge@...lyn.com>, Paul Moore <paul@...l-moore.com>, Stephen Smalley <sds@...ho.nsa.gov>, Eric Paris <eparis@...isplace.org>, Andy Lutomirski <luto@...capital.net>, linux-kernel@...r.kernel.org, linux-bcache@...r.kernel.org, dm-devel@...hat.com, linux-raid@...r.kernel.org, linux-mtd@...ts.infradead.org, linux-fsdevel@...r.kernel.org, linux-security-module@...r.kernel.org, selinux@...ho.nsa.gov Subject: Re: [PATCH v3 4/7] fs: Treat foreign mounts as nosuid On Tue, 17 Nov 2015, Seth Forshee wrote: > From: Andy Lutomirski <luto@...capital.net> > > If a process gets access to a mount from a different user > namespace, that process should not be able to take advantage of > setuid files or selinux entrypoints from that filesystem. Prevent > this by treating mounts from other mount namespaces and those not > owned by current_user_ns() or an ancestor as nosuid. > > This will make it safer to allow more complex filesystems to be > mounted in non-root user namespaces. > > This does not remove the need for MNT_LOCK_NOSUID. The setuid, > setgid, and file capability bits can no longer be abused if code in > a user namespace were to clear nosuid on an untrusted filesystem, > but this patch, by itself, is insufficient to protect the system > from abuse of files that, when execed, would increase MAC privilege. > > As a more concrete explanation, any task that can manipulate a > vfsmount associated with a given user namespace already has > capabilities in that namespace and all of its descendents. If they > can cause a malicious setuid, setgid, or file-caps executable to > appear in that mount, then that executable will only allow them to > elevate privileges in exactly the set of namespaces in which they > are already privileges. > > On the other hand, if they can cause a malicious executable to > appear with a dangerous MAC label, running it could change the > caller's security context in a way that should not have been > possible, even inside the namespace in which the task is confined. > > As a hardening measure, this would have made CVE-2014-5207 much > more difficult to exploit. > > Signed-off-by: Andy Lutomirski <luto@...capital.net> > Signed-off-by: Seth Forshee <seth.forshee@...onical.com> Acked-by: James Morris <james.l.morris@...cle.com> -- James Morris <jmorris@...ei.org> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists