netdev - Re: [PATCH net] netdev: prevent accessing NAPI instances from another namespace

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Message-ID: <677d8f3618080_2821742942a@willemb.c.googlers.com.notmuch>
Date: Tue, 07 Jan 2025 15:31:50 -0500
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: Jakub Kicinski <kuba@...nel.org>, 
 Willem de Bruijn <willemdebruijn.kernel@...il.com>
Cc: davem@...emloft.net, 
 netdev@...r.kernel.org, 
 edumazet@...gle.com, 
 pabeni@...hat.com, 
 stable@...r.kernel.org, 
 jdamato@...tly.com, 
 almasrymina@...gle.com, 
 amritha.nambiar@...el.com, 
 sridhar.samudrala@...el.com
Subject: Re: [PATCH net] netdev: prevent accessing NAPI instances from another
 namespace

Jakub Kicinski wrote:
> On Tue, 07 Jan 2025 08:10:36 -0500 Willem de Bruijn wrote:
> > > +/* must be called under rcu_read_lock(), as we dont take a reference */  
> > 
> > Instead of function comments, invariant checks in code?
> > 
> > Like in dev_get_by_napi_id:
> > 
> >         WARN_ON_ONCE(!rcu_read_lock_held());
> 
> Can I do it as a follow up? Adding the warning to napi_by_id()
> reveals that napi_hash_add() currently walks the list without
> holding the RCU lock :)

Ah I should have noticed that :) Of course, or ignore in this case
then.