netdev - Re: [PATCH v2 bpf-next 0/4] af_unix: Allow BPF LSM to filter SCM

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Message-ID: <20250614204044.2190213-1-kuni1840@gmail.com>
Date: Sat, 14 Jun 2025 13:40:04 -0700
From: Kuniyuki Iwashima <kuni1840@...il.com>
To: paul@...l-moore.com
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Subject: Re: [PATCH v2 bpf-next 0/4] af_unix: Allow BPF LSM to filter SCM_RIGHTS at sendmsg().

From: Paul Moore <paul@...l-moore.com>
Date: Sat, 14 Jun 2025 07:43:46 -0400
> On June 13, 2025 6:24:15 PM Kuniyuki Iwashima <kuni1840@...il.com> wrote:
> > From: Kuniyuki Iwashima <kuniyu@...gle.com>
> >
> > Since commit 77cbe1a6d873 ("af_unix: Introduce SO_PASSRIGHTS."),
> > we can disable SCM_RIGHTS per socket, but it's not flexible.
> >
> > This series allows us to implement more fine-grained filtering for
> > SCM_RIGHTS with BPF LSM.
> 
> My ability to review this over the weekend is limited due to device and 
> network access, but I'll take a look next week.
> 
> That said, it would be good if you could clarify the "filtering" aspect of 
> your comments; it may be obvious when I'm able to look at the full patchset

I meant to mention that just below the quoted part :)

---8<---
Changes:
  v2: Remove SCM_RIGHTS fd scrubbing functionality
---8<---

> in context, but the commit descriptions worry me that perhaps you are still 
> intending on using the LSM framework to cut SCM_RIGHTS payloads from 
> individual messages?  Blocking messages at send time if they contain 
> SCM_RIGHTS is likely okay (pending proper implementation review), but 
> modifying packets in flight in the LSM framework is not.
> 
> Also, a quick administrative note, I see you have marked this as 
> "bpf-next", however given the diffstat of the proposed changes this 
> patchset should go to Linus via the LSM tree and not the BPF tree.

This was to kick the BPF CI for the selftest patch, and the __nullable
arg suffix in patch 3 is BPF specific stuff, but I don't have preference
here and whichever is fine to me.