Re: [PATCH net-next] gtp: annotate PDP lookups under RTNL

[Simon Horman <horms@kernel.org>]

On Wed, Jul 08, 2026 at 01:10:58PM +0200, Paolo Abeni wrote:
> On 7/8/26 12:35 PM, Simon Horman wrote:
> > On Tue, Jul 07, 2026 at 04:51:12PM +0200, Pablo Neira Ayuso wrote:
> >> On Tue, Jul 07, 2026 at 03:28:20PM +0100, Simon Horman wrote:
> >>> On Wed, Jul 01, 2026 at 08:39:25PM +0800, Runyu Xiao wrote:
> >>>> The GTP PDP lookup helpers are shared by RCU-protected data and report
> >>>> paths and RTNL-protected control paths such as gtp_genl_new_pdp(). The
> >>>> helpers walk RCU hlists, but they do not currently pass the RTNL
> >>>> condition for the control-path lookups.
> >>>>
> >>>> Pass lockdep_rtnl_is_held() to the PDP hlist iterators. Existing
> >>>> RCU-reader callers remain valid because the RCU-list macros also accept
> >>>> an active RCU read-side section; the added condition only documents the
> >>>> non-RCU protection already used by RTNL control paths.
> >>>>
> >>>> This was found by our static analysis tool and then manually reviewed
> >>>> against the current tree. The dynamic triage evidence is a
> >>>> target-matched CONFIG_PROVE_RCU_LIST warning; the change is limited
> >>>> to documenting the existing protection contract.
> >>>>
> >>>> This is a lockdep annotation cleanup. It does not change PDP lifetime or
> >>>> hash updates.
> >>>>
> >>>> Signed-off-by: Runyu Xiao <runyu.xiao@seu.edu.cn>
> >>>
> >>> Reviewed-by: Simon Horman <horms@kernel.org>
> >>>
> >>> There is an AI-generated review of this patch available on sashko.dev.
> >>> While I don't believe that the issues raised there should impede progress
> >>> of this patch you may want to look into them as possible follow-up.
> >>
> >> This patch refers to the rtnl_lock, but it is the genetlink mutex that
> >> protects updates on the PDP context list.
> >>
> >> Then, from packet path, rcu lookups are performed.
> >>
> >> I think this patch is not correct.
> > 
> > Hi Pablo,
> > 
> > Of course you are correct.
> > Sorry for not realising this earlier.
> 
> Human slop here made me wrongly apply this patch. Could either of you
> please share a formal revert?

Sure, will do.