Re: [PATCH 2/9] signal/seccomp: Refactor seccomp signal and coredump generation

[Eric W. Biederman]

Kees Cook <keescook@xxxxxxxxxxxx> writes:

> On Thu, Jun 24, 2021 at 01:59:55PM -0500, Eric W. Biederman wrote:
>> 
>> Factor out force_sig_seccomp from the seccomp signal generation and
>> place it in kernel/signal.c.  The function force_sig_seccomp takes a
>> paramter force_coredump to indicate that the sigaction field should be
>> reset to SIGDFL so that a coredump will be generated when the signal
>> is delivered.
>
> Ah! This is the part I missed when I was originally trying to figure
> out the coredump stuff. It's the need for setting a default handler
> (i.e. doing a coredump)?

Yes.  If we don't force the handler to SIG_DFL someone might catch
SIGSYS.

>> force_sig_seccomp is then used to replace both seccomp_send_sigsys
>> and seccomp_init_siginfo.
>> 
>> force_sig_info_to_task gains an extra parameter to force using
>> the default signal action.
>> 
>> With this change seccomp is no longer a special case and there
>> becomes exactly one place do_coredump is called from.
>
> Looks good to me. This may benefit from force_sig_seccomp() to be wrapped
> in an #ifdef CONFIG_SECCOMP.

At which point Linus will probably be grumpy with me for introducing
#ifdefs.

I suspect seccomp at this point is sufficiently common that is probably
more productive to figure out how to remove #ifdef  CONFIG_SECCOMP.

> (This patch reminds me that the seccomp self tests don't check for core
> dumps...)

This patch is slightly wrong in that it kept the call to do_group_exit
when it can never be reached.

Eric