linux-kernel - Re: [PATCH] pidfd: prevent creation of pidfds for kthreads

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

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <93296f30-1a3c-44b6-91d1-61408e1d9270@leemhuis.info>
Date: Fri, 23 Aug 2024 07:23:12 +0200
From: "Linux regression tracking (Thorsten Leemhuis)"
 <regressions@...mhuis.info>
To: stable@...r.kernel.org, Greg KH <gregkh@...uxfoundation.org>,
 Sasha Levin <sashal@...nel.org>
Cc: linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
 Oleg Nesterov <oleg@...hat.com>, Aleksa Sarai <cyphar@...har.com>,
 Tycho Andersen <tandersen@...flix.com>,
 Daan De Meyer <daan.j.demeyer@...il.com>, Tejun Heo <tj@...nel.org>,
 Eric Biggers <ebiggers@...nel.org>, Christian Brauner <brauner@...nel.org>,
 Linux kernel regressions list <regressions@...ts.linux.dev>
Subject: Re: [PATCH] pidfd: prevent creation of pidfds for kthreads

On 19.08.24 10:41, Christian Brauner wrote:
> On Sat, Aug 17, 2024 at 08:58:18PM GMT, Eric Biggers wrote:
>> On Wed, Jul 31, 2024 at 12:01:12PM +0200, Christian Brauner wrote:
>>> It's currently possible to create pidfds for kthreads but it is unclear
>>> what that is supposed to mean. Until we have use-cases for it and we
>>> figured out what behavior we want block the creation of pidfds for
>>> kthreads.
>>>
>>> Fixes: 32fcb426ec00 ("pid: add pidfd_open()")
>>> Cc: stable@...r.kernel.org
>>> Signed-off-by: Christian Brauner <brauner@...nel.org>
>>> ---
>>>  kernel/fork.c | 25 ++++++++++++++++++++++---
>>>  1 file changed, 22 insertions(+), 3 deletions(-)
>>
>> Unfortunately this commit broke systemd-shutdown's ability to kill processes,
>> which makes some filesystems no longer get unmounted at shutdown.
>>
>> It looks like systemd-shutdown relies on being able to create a pidfd for any
>> process listed in /proc (even a kthread), and if it gets EINVAL it treats it a
>> fatal error and stops looking for more processes...
> 
> Thanks for the report!
> I talked to Daan De Meyer who made that change and he said that this
> must a systemd version that hasn't gotten his fixes yet. In any case, if
> this causes regression then I'll revert it right now. See the appended
> revert.

Greg, Sasha, JFYI in case you are not already aware of it: I by
chance[1] noticed that the patch Christian plans to revert is still in
the 6.10-queue. You might want to drop it (or apply the revert as well,
which is in -next, but not yet in mainline afaics).

Ciao, Thorsten

[1] after I noticed this thread a third time, this time via some SELinux
problems it caused in Fedora land:
https://bugzilla.redhat.com/show_bug.cgi?id=2306818
https://bugzilla.redhat.com/show_bug.cgi?id=2305270