Re: [RFC PATCH 0/2] seccomp: defer syscall_rollback() to get_signal()

[Oleg Nesterov <oleg@redhat.com>]

On 04/14, Oleg Nesterov wrote:
>
> Kees, Andy, et al, please comment. I think the usage of syscall_rollback()
> in __seccomp_filter() is not right.

I'll recheck, but in fact this logic looks broken... force_sig_seccomp() assumes
that it can't race with (say) SIGSEGV which has a handler. And 2/2 makes the things
slightly worse. So self-nack for now.

> In fact I think that syscall_exit_work() should do nothing if a
> syscall was rejected with force_sig_seccomp() by __seccomp_filter().
> If nothing else, the syscall was never actually executed.
>
> Perhaps we can add a new SYSCALL_WORK_SYSCALL_XXX to SYSCALL_WORK_EXIT.
> seccomp_nack_syscall() can set this flag, and syscall_exit_work() can do
>
> 	if (work & SYSCALL_WORK_SYSCALL_XXX) {
> 		clear_syscall_work(SYSCALL_XXX); // for the !force_coredump case
> 		return;
> 	}
>
> after the "if (SYSCALL_WORK_SYSCALL_USER_DISPATCH)" block.
>
> But I didn't dare to do such a change.
>
> What do you think?

I'll try to send a patch based on above this week.

Oleg.