From: Colin Walters <walters@verbum.org>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Casey Schaufler <casey@schaufler-ca.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Jamie Lokier <jamie@shareable.org>,
Will Drewry <wad@chromium.org>,
linux-kernel@vger.kernel.org, keescook@chromium.org,
john.johansen@canonical.com, serge.hallyn@canonical.com,
coreyb@linux.vnet.ibm.com, pmoore@redhat.com, eparis@redhat.com,
djm@mindrot.org, segoon@openwall.com, rostedt@goodmis.org,
jmorris@namei.org, scarybeasts@gmail.com, avi@redhat.com,
penberg@cs.helsinki.fi, viro@zeniv.linux.org.uk, mingo@elte.hu,
akpm@linux-foundation.org, khilman@ti.com,
borislav.petkov@amd.com, amwang@redhat.com, oleg@redhat.com,
ak@linux.intel.com, eric.dumazet@gmail.com, gregkh@suse.de,
dhowells@redhat.com, daniel.lezcano@free.fr,
linux-fsdevel@vger.kernel.org,
linux-security-module@vger.kernel.org, olofj@chromium.org,
mhalcrow@google.com, dlaor@redhat.com, corbet@lwn.net,
alan@lxorguk.ukuu.org.uk
Subject: Re: [PATCH v2 0/4] PR_SET_NO_NEW_PRIVS, unshare, and chroot
Date: Mon, 16 Jan 2012 16:47:00 -0500 [thread overview]
Message-ID: <1326750422.3467.31.camel@lenny> (raw)
In-Reply-To: <CALCETrW3WyzaGBMJZzfohD=MRwdmeV9bAo4Leg1gaSnPL5URpg@mail.gmail.com>
On Mon, 2012-01-16 at 13:25 -0800, Andy Lutomirski wrote:
> The MS_NOSUID semantics are somewhat ridiculous for selinux,
I don't see how they're ridiculous.
> and I'd
> rather not make them match for no_new_privs.
Note your patch for selinux does exactly the same thing in the NOSUID
case and your NO_NEW_PRIVS flag. Right?
- if (bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID)
+ if ((bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID) ||
+ (bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS))
new_tsec->sid = old_tsec->sid;
> AppArmor completely
> ignores MS_NOSUID,
Ugh...well, I guess if it doesn't store any security data associated
with files, only with file names, then there's nothing for it to do.
Like I said before though, I think SELinux is the only sane LSM.
> CLONE_NEWNET seems more likely to consume significant kernel resources
> than the others.
This actually brings up something we need to think about - if we're
heading towards being able to do bind mounts as non-root (which is
necessary for me) we'd need limits on e.g. the number of mounts that can
be made for a given uid/cgroup.
I have a picked-from-thin-air hardcoded limit of 50 in my setuid binary,
but I just realized that that's 50*RLIMIT_NPROC which is kind of
large...
> I didn't have a great reason, though. Unsharing the
> filesystem namespace is possibly dangerous because it could prevent an
> unmount in the original namespace from taking effect everywhere.
Hmmm...hadn't considered that either. So the issue here is if a server
admin has e.g. a NFS mount and my build tool makes a new copy of the
mount namespace, a process may still have it busy when she goes to
unmount it?
> Fair enough. I may add this in v3. seccomp is an even better
> solution, though :)
Yeah, definitely more flexible, though realistic use of seccomp depends
on someone making a nice userspace tool to compile sets of syscalls like
"no networking".
next prev parent reply other threads:[~2012-01-16 21:47 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-16 0:37 [PATCH v2 0/4] PR_SET_NO_NEW_PRIVS, unshare, and chroot Andy Lutomirski
2012-01-16 0:37 ` [PATCH v2 1/4] Add PR_{GET,SET}_NO_NEW_PRIVS to prevent execve from granting privs Andy Lutomirski
2012-01-16 17:33 ` Oleg Nesterov
2012-01-16 20:15 ` Andy Lutomirski
2012-01-16 0:37 ` [PATCH v2 2/4] Fix apparmor for PR_{GET,SET}_NO_NEW_PRIVS Andy Lutomirski
2012-01-16 0:37 ` [PATCH v2 3/4] Allow unprivileged CLONE_NEWUTS and CLONE_NEWIPC with no_new_privs Andy Lutomirski
2012-01-16 0:37 ` [PATCH 4/4] Allow unprivileged chroot when safe Andy Lutomirski
2012-01-16 0:45 ` Linus Torvalds
2012-01-16 1:08 ` Andy Lutomirski
2012-01-16 19:26 ` Colin Walters
2012-01-16 20:18 ` Andy Lutomirski
2012-01-17 10:14 ` Jamie Lokier
2012-01-16 20:06 ` Al Viro
2012-01-16 20:15 ` Andy Lutomirski
2012-01-16 20:26 ` Al Viro
2012-01-17 16:23 ` Oleg Nesterov
2012-01-17 16:31 ` Andy Lutomirski
2012-01-16 1:04 ` [PATCH v2 0/4] PR_SET_NO_NEW_PRIVS, unshare, and chroot Andy Lutomirski
2012-01-16 20:49 ` Colin Walters
2012-01-16 21:25 ` Andy Lutomirski
2012-01-16 21:47 ` Colin Walters [this message]
2012-01-16 21:57 ` Andy Lutomirski
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