Re: [PATCH v2 2/3] seccomp: Introduce addfd ioctl to seccomp user notifier

On Sat, May 30, 2020 at 03:58:27PM +0200, Christian Brauner wrote:

On Sat, May 30, 2020 at 05:17:24AM +0200, Jann Horn wrote:

quoted

On Sat, May 30, 2020 at 4:43 AM Kees Cook [off-list ref] wrote:

quoted

I mean, yes, that's certainly better, but it just seems a shame that
everyone has to do the get_unused/put_unused dance just because of how
SCM_RIGHTS does this weird put_user() in the middle.

Can anyone clarify the expected failure mode from SCM_RIGHTS? Can we
move the put_user() after instead?

Honestly, I think trying to remove file descriptors and such after
-EFAULT is a waste of time. If userspace runs into -EFAULT, userspace

[...]

There's really no point in trying to save a broken scm message imho.

Right -- my concern is about stuffing a fd into a process without it
knowing (this is likely an overly paranoid concern, given that if the
process is getting EFAULT at the end of a list of fds, all the prior
ones will be installed too..)

-- 
Kees Cook