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

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Date:   Wed,  9 Feb 2022 18:53:18 -0800
From:   Kees Cook <keescook@...omium.org>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     Kees Cook <keescook@...omium.org>,
        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: [PATCH 0/3] signal: HANDLER_EXIT should clear SIGNAL_UNKILLABLE

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.)

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(-)

-- 
2.30.2