From: Oleg Nesterov <oleg@redhat.com>
To: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: akpm@linux-foundation.org, viro@ZenIV.linux.org.uk,
keescook@chromium.org, mhocko@suse.cz, snanda@chromium.org,
dserrg@gmail.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/4] check_unsafe_exec: kill the dead -EAGAIN and clear_in_exec logic
Date: Sat, 23 Nov 2013 16:32:18 +0100 [thread overview]
Message-ID: <20131123153218.GA22071@redhat.com> (raw)
In-Reply-To: <528FC5E8.20406@jp.fujitsu.com>
On 11/22, KOSAKI Motohiro wrote:
>
> >> I have found no problem in this patch. However, I have a very basic question.
> >> Why do we need to keep fs->in_exec?
> >
> > To ensure that a sub-thread can't create a new process with the same
> > ->fs while we are doing exec without LSM_UNSAFE_SHARE, I guess. This
> > is only for security/ code.
>
> But in LSM_UNSAFE_SHARE case, we have no check, right? I'm amazing why
> we don't need anything.
Yes. We rely on security/ code in this case, it can nack this exec if it
looks unsafe.
IOW. If LSM_UNSAFE_SHARE is not set, we promise that this fs has a single
user: the execing thread (it will kill other subthreads which can have the
same fs). That is why we need to cancel any attempt to create another
CLONE_FS process in between.
But let me repeat this is only my speculations, I know nothing about selinux
and selinux_bprm_set_creds() in particular. Although it looks obvious that
potentially exec with the shared ->fs has the additional security problems.
Kosaki, thank you for review!
Oleg.
next prev parent reply other threads:[~2013-11-23 15:31 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-11-22 17:54 [PATCH 0/4] in_exec/etc cleanups Oleg Nesterov
2013-11-22 17:54 ` [PATCH 1/4] check_unsafe_exec: use while_each_thread() rather than next_thread() Oleg Nesterov
2013-11-22 19:42 ` KOSAKI Motohiro
2013-11-22 20:24 ` Oleg Nesterov
2013-11-22 20:32 ` KOSAKI Motohiro
2013-11-22 17:54 ` [PATCH 2/4] check_unsafe_exec: kill the dead -EAGAIN and clear_in_exec logic Oleg Nesterov
2013-11-22 20:27 ` KOSAKI Motohiro
2013-11-22 20:49 ` Oleg Nesterov
2013-11-22 21:00 ` KOSAKI Motohiro
2013-11-23 15:32 ` Oleg Nesterov [this message]
2013-11-22 17:54 ` [PATCH 3/4] exec: move the final allow_write_access/fput into free_bprm() Oleg Nesterov
2013-11-22 20:29 ` KOSAKI Motohiro
2013-11-23 19:22 ` Kees Cook
2013-11-22 17:54 ` [PATCH 4/4] kill task_struct->did_exec Oleg Nesterov
2013-11-22 19:46 ` KOSAKI Motohiro
2013-11-22 20:33 ` [PATCH v2 " Oleg Nesterov
2013-11-22 20:33 ` KOSAKI Motohiro
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