On Mon, Feb 27, 2012 at 12:34 PM, Eric Paris [off-list ref] wrote:

On Mon, 2012-02-27 at 12:00 -0800, Kees Cook wrote:

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On Mon, Feb 27, 2012 at 11:25 AM, Eric Paris [off-list ref] wrote:

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On Mon, 2012-02-27 at 10:55 -0800, Kees Cook wrote:

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On Mon, Feb 27, 2012 at 8:49 AM, Eric Paris [off-list ref] wrote:

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You mean as used in audit_log_exit() ? It looks like that depends on a
lot of state cached in __audit_syscall_entry() and finally triggered
in __audit_syscall_exit() (and ..._free()). I don't think this is
really want seccomp wants to be involved in.

By CONFIG_AUDITSC, you mean CONFIG_AUDITSYSCALL? Without that set,
audit_seccomp is a no-op.

The reason compat needs to be reported (or rather, arch) is because
just reporting syscall is ambiguous. It either needs arch or compat to
distinguish it.

Yes, that is what I mean and you are right.  You shouldn't push the
syscall in this record either.  If !audit_dummy_context() you are
already going to get arch, syscall, and a0-a4 in the associated audit
record.  Please do not duplicate that info.

Ah, in that case, please ignore the patch I just sent. Heh.

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It might make sense to have a separate audit_seccomp() path when
audit_dummy_context() which includes arch, syscall, and a0-a4.

Ah! I think I understand what you mean now. If audit_dummy_context(),
then the syscall, arch, and a0-a4 were not already collected. Gotcha.

How do you envision it looking? I still see it as two distinct events
(the syscall itself, and the rejection). Would you want those details
added to the context structure to be reported at ..._exit() time? It
seems like context->type couldn't be used to see if those fields were
valid.

Something like:

void __audit_seccomp(unsigned long syscall, long signr)
{
        struct audit_buffer *ab;

        if (!audit_dummy_context()) {
                struct audit_context *context = current->audit_context;
                context->syscall_signr = signr;
                context->syscall_ip = KSTK_EIP(current);
                return;
        }

        ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_ANOM_ABEND);
        audit_log_abend(ab, "seccomp", signr);
        audit_log_format(ab, " syscall=%ld", syscall);
        audit_log_format(ab, " ip=0x%lx", KSTK_EIP(current));
        audit_log_end(ab);
}

And then report syscall_ip and syscall_signr if syscall_signr != 0 in
the _exit()? I think everything else from audit_log_abend() will end
up in the _exit() report.

quoted

It is my fault (85e7bac3) that we have syscall at all, but I'm on a new
crusade to remove audit record duplication.  So I'd happily see a patch
in this series that removes that instead of adds to it.

Well, I think the abend reporting is nice; I'd hate to see that
totally removed. The seccomp case is a bit different, I agree. I could
see it either way.

Once again I send you down a bad path.  Your original patch was the
best.  We should consider including a0-aX in a future version.  I was
mistaken in foolishly believing that audit_syscall_entry() was done
before secure_computing().  But if you look, that isn't the case.
Please pretend I never said anything as you had it right the first time.

Heh, okay. But now I know more about audit, so that's good. :)

-Kees

-- 
Kees Cook
ChromeOS Security