linux-hardening - Re: [PATCH 0/3] signal: HANDLER_EXIT should clear SIGNAL

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Date:   Thu, 10 Feb 2022 12:17:50 -0600
From:   "Eric W. Biederman" <ebiederm@...ssion.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     Robert Święcki <robert@...ecki.net>,
        Andy Lutomirski <luto@...capital.net>,
        Will Drewry <wad@...omium.org>, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH 0/3] signal: HANDLER_EXIT should clear SIGNAL_UNKILLABLE

Kees Cook <keescook@...omium.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'll be sending this to Linus after a bit more testing...
>
> Thanks,
>
> -Kees
>
> Kees Cook (3):
>   signal: HANDLER_EXIT should clear SIGNAL_UNKILLABLE
>   seccomp: Invalidate seccomp mode to catch death failures
>   samples/seccomp: Adjust sample to also provide kill option
>
>  kernel/seccomp.c          | 10 ++++++++++
>  kernel/signal.c           |  5 +++--
>  samples/seccomp/dropper.c |  9 +++++++--
>  3 files changed, 20 insertions(+), 4 deletions(-)

Eric