From: Casey Schaufler <casey@schaufler-ca.com>
To: Florian Weimer <fweimer@redhat.com>,
apparmor@lists.ubuntu.com, linux-security-module@vger.kernel.org,
selinux@vger.kernel.org, linux-api@vger.kernel.org
Cc: "H. Peter Anvin" <hpa@zytor.com>, Arnd Bergmann <arnd@arndb.de>
Subject: Re: Security modules and sending signals within the same process
Date: Fri, 30 Nov 2018 09:54:44 -0800 [thread overview]
Message-ID: <2c3e813c-f56a-3354-1299-30b0646f40e1@schaufler-ca.com> (raw)
In-Reply-To: <87lg5asilo.fsf@oldenburg.str.redhat.com>
On 11/30/2018 7:14 AM, Florian Weimer wrote:
> Is it guaranteed that tasks in the same thread group can always send
> signals to each other, irrespective of their respective credentials
> structs?
No. An LSM may chose to disallow this based on just about any
criteria it desires.
> It's not clear to me whether this is always possible based on the
> security_task_kill implementations I've examined.
SELinux, Smack and AppArmor make their decisions based on
the task_struct credential, so if it's possible to change
the LSM attributes at the task granularity, it's possible
to have a process that can't always talk to itself.
> I want to support per-thread setresuid/setresgid,
That's pretty dangerous in its own right. Effectively
the process containing the threads has multiple UIDs.
That complicates the DAC model significantly.
> but we also use
> signals for inter-thread communication.
It's unfortunate that no one has seriously proposed
mode bits on processes for signal delivery. The UID
matching policy is inconvenient in a lot of cases.
Hmmm...
> This is mainly for thread
> cancellation; the setxgid stuff isn't needed for threads with private
> credentials. I wonder if I need to disable cancellation for threads
> with such credentials.
>
> Thanks,
> Florian
>
next prev parent reply other threads:[~2018-11-30 17:54 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-30 15:14 Security modules and sending signals within the same process Florian Weimer
2018-11-30 16:02 ` Stephen Smalley
2018-12-11 10:42 ` Florian Weimer
2018-11-30 17:54 ` Casey Schaufler [this message]
2018-11-30 18:00 ` Florian Weimer
2018-11-30 23:38 ` [apparmor] " John Johansen
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=2c3e813c-f56a-3354-1299-30b0646f40e1@schaufler-ca.com \
--to=casey@schaufler-ca.com \
--cc=apparmor@lists.ubuntu.com \
--cc=arnd@arndb.de \
--cc=fweimer@redhat.com \
--cc=hpa@zytor.com \
--cc=linux-api@vger.kernel.org \
--cc=linux-security-module@vger.kernel.org \
--cc=selinux@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).