From: ebiederm@xmission.com (Eric W. Biederman)
To: Aleksa Sarai <asarai@suse.de>
Cc: linux-kernel@vger.kernel.org, Kees Cook <keescook@chromium.org>,
Roland McGrath <roland@hack.frob.com>,
linux-api@vger.kernel.org,
Linux Containers <containers@lists.linux-foundation.org>,
Oleg Nesterov <oleg@redhat.com>,
David Howells <dhowells@redhat.com>,
Al Viro <viro@ZenIV.linux.org.uk>,
Thomas Gleixner <tglx@linutronix.de>,
Linus Torvalds <torvalds@linux-foundation.org>,
Ingo Molnar <mingo@kernel.org>,
"Michael Kerrisk \(man-pages\)" <mtk.manpages@gmail.com>
Subject: Re: [PATCH 00/26] Fixing wait, exit, ptrace, exec, and CLONE_THREAD
Date: Wed, 07 Jun 2017 06:36:48 -0500 [thread overview]
Message-ID: <87ink8vxkf.fsf@xmission.com> (raw)
In-Reply-To: <dd16b1bb-e99e-69f2-72f4-1be4cb24d18d@suse.de> (Aleksa Sarai's message of "Wed, 7 Jun 2017 05:40:21 +1000")
Aleksa Sarai <asarai@suse.de> writes:
>> Another easy entry point is to see that a multi-threaded setuid won't
>> change the credentials on a zombie thread group leader. Which can allow
>> sending signals to a process that the credential change should forbid.
>> This is in violation of posix and the semantics we attempt to enforce in
>> linux.
>
> I might be completely wrong on this point (and I haven't looked at the patches),
> but I was under the impression that multi-threaded set[ug]id was implemented in
> userspace (by glibc's nptl(7) library that uses RT signals internally to get
> each thread to update their credentials). And given that, I wouldn't be
> surprised (as a user) that zombie threads will have stale credentials (glibc
> isn't running in those threads anymore).
>
> Am I mistaken in that belief?
Would you be surprised if you learned that if your first thread
exits, it will become a zombie and persist for the lifetime of your
process?
Furthermore all non-thread specific signals will permission check
against that first zombie thread.
Which I think makes this surprising even if you know that setuid is
implemented in userspace.
Eric
next prev parent reply other threads:[~2017-06-07 11:43 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-06 19:01 [PATCH 00/26] Fixing wait, exit, ptrace, exec, and CLONE_THREAD Eric W. Biederman
2017-06-06 19:03 ` [PATCH 01/26] alpha: Remove unused TASK_GROUP_LEADER Eric W. Biederman
2017-06-06 19:03 ` [PATCH 02/26] cgroup: Don't open code tasklist_empty() Eric W. Biederman
2017-06-06 19:03 ` [PATCH 03/26] signal: Do not perform permission checks when sending pdeath_signal Eric W. Biederman
2017-06-06 20:01 ` Linus Torvalds
2017-06-07 11:23 ` Eric W. Biederman
2017-06-06 21:42 ` Richard Weinberger
2017-06-06 19:03 ` [PATCH 04/26] signal: Make group_send_sig_info static Eric W. Biederman
2017-06-06 19:03 ` [PATCH 05/26] exit: Remove the pointless clearing of SIGPENDING in __exit_signal Eric W. Biederman
2017-06-06 19:03 ` [PATCH 06/26] rlimit: Remove unnecessary grab of tasklist_lock Eric W. Biederman
2017-06-07 12:36 ` Oleg Nesterov
2017-06-07 14:08 ` Eric W. Biederman
2017-06-06 19:03 ` [PATCH 07/26] pidns: Improve the error handling in alloc_pid Eric W. Biederman
2017-06-06 19:03 ` [PATCH 08/26] exit: Make the runqueue rcu safe Eric W. Biederman
2017-06-07 13:16 ` Oleg Nesterov
2017-06-06 19:03 ` [PATCH 09/26] signal: Don't allow sending SIGKILL or SIGSTOP to init Eric W. Biederman
2017-06-06 19:03 ` [PATCH 10/26] ptrace: Simplify ptrace_detach & exit_ptrace Eric W. Biederman
2017-06-06 19:03 ` [PATCH 11/26] wait: Properly implement __WCLONE handling in the presence of exec and ptrace Eric W. Biederman
2017-06-06 19:03 ` [PATCH 12/26] wait: Directly test for the two cases where wait_task_zombie is called Eric W. Biederman
2017-06-06 19:03 ` [PATCH 13/26] wait: Remove unused delay_group_leader Eric W. Biederman
2017-06-06 19:03 ` [PATCH 14/26] wait: Move changing of ptrace from wait_consider_task into wait_task_stopped Eric W. Biederman
2017-06-06 19:03 ` [PATCH 15/26] wait: Don't delay !ptrace_reparented leaders Eric W. Biederman
2017-06-06 19:03 ` [PATCH 16/26] exit: Fix reporting a ptraced !reparented leader has exited Eric W. Biederman
2017-06-06 19:03 ` [PATCH 17/26] exit: Rework the exit states for ptracees Eric W. Biederman
2017-06-06 19:03 ` [PATCH 18/26] wait: Fix WSTOPPED on a ptraced child Eric W. Biederman
2017-06-06 19:03 ` [PATCH 19/26] wait: Simpler code for clearing notask_error in wait_consider_task Eric W. Biederman
2017-06-06 19:03 ` [PATCH 20/26] wait: Don't pass the list to wait_consider_task Eric W. Biederman
2017-06-06 19:03 ` [PATCH 21/26] wait: Optmize waitpid Eric W. Biederman
2017-06-06 19:03 ` [PATCH 22/26] exit: Fix auto-wait of ptraced children Eric W. Biederman
2017-06-06 19:03 ` [PATCH 23/26] signal: Fix SIGCONT before group stop completes Eric W. Biederman
2017-06-06 19:03 ` [PATCH 24/26] signal: In ptrace_stop improve identical signal detection Eric W. Biederman
2017-06-06 19:03 ` [PATCH 25/26] signal: In ptrace_stop use CLD_TRAPPED in all ptrace signals Eric W. Biederman
2017-06-06 19:03 ` [PATCH 26/26] pidns: Ensure zap_pid_ns_processes always terminates Eric W. Biederman
2017-06-06 19:40 ` [PATCH 00/26] Fixing wait, exit, ptrace, exec, and CLONE_THREAD Aleksa Sarai
2017-06-07 11:36 ` Eric W. Biederman [this message]
2017-06-07 12:21 ` Aleksa Sarai
2017-06-06 20:07 ` Linus Torvalds
2017-06-07 15:59 ` Eric W. Biederman
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=87ink8vxkf.fsf@xmission.com \
--to=ebiederm@xmission.com \
--cc=asarai@suse.de \
--cc=containers@lists.linux-foundation.org \
--cc=dhowells@redhat.com \
--cc=keescook@chromium.org \
--cc=linux-api@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@kernel.org \
--cc=mtk.manpages@gmail.com \
--cc=oleg@redhat.com \
--cc=roland@hack.frob.com \
--cc=tglx@linutronix.de \
--cc=torvalds@linux-foundation.org \
--cc=viro@ZenIV.linux.org.uk \
/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