From: Kees Cook <keescook@chromium.org>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: "Robert Święcki" <robert@swiecki.net>,
"Andy Lutomirski" <luto@amacapital.net>,
"Will Drewry" <wad@chromium.org>,
linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org
Subject: Re: [PATCH 0/3] signal: HANDLER_EXIT should clear SIGNAL_UNKILLABLE
Date: Thu, 10 Feb 2022 10:41:57 -0800 [thread overview]
Message-ID: <202202101033.9C04563D9@keescook> (raw)
In-Reply-To: <871r0a8u29.fsf@email.froward.int.ebiederm.org>
On Thu, Feb 10, 2022 at 12:17:50PM -0600, Eric W. Biederman wrote:
> Kees Cook <keescook@chromium.org> writes:
>
> > Hi,
> >
> > This fixes the signal refactoring to actually kill unkillable processes
> > when receiving a fatal SIGSYS from seccomp. Thanks to Robert for the
> > report and Eric for the fix! I've also tweaked seccomp internal a bit to
> > fail more safely. This was a partial seccomp bypass, in the sense that
> > SECCOMP_RET_KILL_* didn't kill the process, but it didn't bypass other
> > aspects of the filters. (i.e. the syscall was still blocked, etc.)
>
> Any luck on figuring out how to suppress the extra event?
I haven't found a good single indicator of a process being in an "I am dying"
state, and even if I did, it seems every architecture's exit path would
need to add a new test.
The best approach seems to be clearing the TIF_*WORK* bits, but that's
still a bit arch-specific. And I'm not sure which layer would do that.
At what point have we decided the process will not continue? More
than seccomp was calling do_exit() in the middle of a syscall, but those
appear to have all been either SIGKILL or SIGSEGV?
--
Kees Cook
next prev parent reply other threads:[~2022-02-10 18:42 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-10 2:53 [PATCH 0/3] signal: HANDLER_EXIT should clear SIGNAL_UNKILLABLE Kees Cook
2022-02-10 2:53 ` [PATCH 1/3] " Kees Cook
2022-02-10 16:18 ` Jann Horn
2022-02-10 17:37 ` Kees Cook
2022-02-10 18:01 ` Jann Horn
2022-02-10 18:12 ` Eric W. Biederman
2022-02-10 21:09 ` Kees Cook
2022-02-11 20:15 ` Jann Horn
2022-02-10 18:16 ` Eric W. Biederman
2022-02-10 2:53 ` [PATCH 2/3] seccomp: Invalidate seccomp mode to catch death failures Kees Cook
2022-02-10 2:53 ` [PATCH 3/3] samples/seccomp: Adjust sample to also provide kill option Kees Cook
2022-02-10 18:17 ` [PATCH 0/3] signal: HANDLER_EXIT should clear SIGNAL_UNKILLABLE Eric W. Biederman
2022-02-10 18:41 ` Kees Cook [this message]
2022-02-10 18:58 ` Eric W. Biederman
2022-02-10 20:43 ` Kees Cook
2022-02-10 22:48 ` Eric W. Biederman
2022-02-11 1:26 ` Kees Cook
2022-02-11 1:47 ` Eric W. Biederman
2022-02-11 2:53 ` Kees Cook
2022-02-11 12:54 ` Robert Święcki
2022-02-11 17:46 ` Eric W. Biederman
2022-02-11 18:57 ` Robert Święcki
2022-02-11 20:01 ` Kees Cook
2022-02-11 19:58 ` Kees Cook
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