On Thu, Feb 26, 2026 at 06:07:41PM +0100, Sabrina Dubroca via Devel wrote:

2026-01-27, 11:42:01 +0100, Antony Antony wrote:

quoted

The nlsk field in struct netns_xfrm is RCU-protected, as seen by
the use of rcu_assign_pointer() and RCU_INIT_POINTER() when updating
it.
However, the field lacks the __rcu annotation, and most read-side
accesses don't use rcu_dereference().

Add the missing __rcu annotation and convert all read-side accesses to
use rcu_dereference() for correctness and to silence sparse warnings.

Sparse warning reported by NIPA allmodconfig test when modifying
net/xfrm/xfrm_user.c. The warning is a pre-existing issue in
xfrm_nlmsg_multicast(). This series added a new call to this function
and NIPA testing reported a new warning was added by this series.

To reproduce (requires sparse):
make C=2 net/xfrm/
net/xfrm/xfrm_user.c:1574:29: error: incompatible types in comparison
expression (different address spaces):
net/xfrm/xfrm_user.c:1574:29:    struct sock [noderef] __rcu *
net/xfrm/xfrm_user.c:1574:29:    struct sock *

BTW, after this, sparse will complain about the other accesses to nlsk
in net/xfrm/xfrm_user.c (in the nlmsg_unicast(net->xfrm.nlsk, ...)
calls).

Indeed there are more sparse warning. I am glad to hear you working on a 
borader patch!

I stayed focused on this one since it was directly triggered by my patch
series, and I couldn't find much guidance on the others easily.

I have a patch adding this __rcu annotation, and fixing the warnings
that it causes. It's part of the series I'm planning to submit very
soon, which fixes a lot of rcu-related warnings in net/xfrm/*.

I am looking forward to this. I'll keep my patch for now as a fix. If your 
series lands first, I'm happy to drop mine.

-antony