Re: [PATCH] seccomp: passthrough uretprobe systemcall without filtering

Kees Cook
2025-01-27T19:33:41Z

On Mon, Jan 27, 2025 at 11:24:02AM -0800, Eyal Birger wrote:
> Hi Kees,
>
> On Mon, Jan 20, 2025 at 1:34 PM Kees Cook <kees@kernel.org> wrote:
> >
> > On Sat, Jan 18, 2025 at 07:39:25PM -0800, Eyal Birger wrote:
> > > Alternatively, maybe this syscall implementation should be reverted?
> >
> > Honestly, that seems the best choice. I don't think any thought was
> > given to how it would interact with syscall interposers (including
> > ptrace, strict mode seccomp, etc).
>
> I don't know if you noticed Andrii's and others' comments on this [1].
>
> Given that:
> - this issue requires immediate remediation
> - there seems to be pushback for reverting the syscall implementation
> - filtering uretprobe is not within the capabilities of seccomp without this
> syscall (so reverting the syscall is equivalent to just passing it through
> seccomp)
>
> is it possible to consider applying this current fix, with the possibility of
> extending seccomp in the future to support filtering uretprobe if deemed
> necessary (for example by allowing userspace to define a stricter policy)?

I still think this is a Docker problem, but I agree that uretprobe
without syscall is just as unfilterable as seccomp ignoring the syscall.

Can you please update the patch to use the existing action_cache bitmaps
instead of adding an open-coded check? We can consider adding
syscall_restart to this as well in the future...

--
Kees Cook