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  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]
Date:   Thu, 10 Feb 2022 12:58:07 -0600
From:   "Eric W. Biederman" <>
To:     Kees Cook <>
Cc:     Robert Święcki <>,
        Andy Lutomirski <>,
        Will Drewry <>,,
Subject: Re: [PATCH 0/3] signal: HANDLER_EXIT should clear SIGNAL_UNKILLABLE

Kees Cook <> writes:

> On Thu, Feb 10, 2022 at 12:17:50PM -0600, Eric W. Biederman wrote:
>> Kees Cook <> 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 "I am dying" state for a task is fatal_signal_pending, at least
before get_signal is reached, for a process there is SIGNAL_GROUP_EXIT.
Something I am busily cleaning up and making more reliable at the

What is the event that is happening?  Is it
tracehook_report_syscall_exit or something else?

>From the bits I have seen it seems like something else.

> 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?

This is where I get confused what TIF_WORK bits matter?

I expect if anything else mattered we would need to change it to

I made a mistake conflating to cases and I want to make certain I
successfully separate those two cases at the end of the day.


Powered by blists - more mailing lists