Re: [PATCH] x86/ptrace: Remove questionable TS_COMPAT usage in ptrace

[Oleg Nesterov]

On 06/20, Andy Lutomirski wrote:
>
> On Mon, Jun 20, 2016 at 8:24 AM, Oleg Nesterov <oleg@xxxxxxxxxx> wrote:
> >
> > How about the simple change below for now? IIRC 32-bit task can't use
> > "syscall" so if syscall_get_nr() >= 0 then even the wrong TS_COMPAT is
> > not that bad, even if it "leaks" to user-mode.
>
> Hmm.  That should fix the minor security issue, but it will even
> further break cross-arch tracing: now a 32-bit tracer tracing a 64-bit
> task that does int $0x80 will malfunction even more than it would
> have.

This is broken in any case. I mean, a 32-bit debugger can't really
debug a 64-bit task.

I don't think this change makes the things really worse.

> Also, it relies on bizarre arch details IMO.

Heh,  it looks as if your patch do not ;)

> I think I prefer my version, coming momentarily.

I disagree... I don't really understand why do we need the additional
complications for the minimal fix which doesn't look very nice anyway.

But I won't argue, and your patch looks correct to me.

Oleg.