[PATCH net] psp: use unrcu_pointer() for the cmpxchg() on netdev psp_dev

[PATCH net] psp: use unrcu_pointer() for the cmpxchg() on netdev psp_dev

[Wei Wang]

From: Wei Wang <weibunny@fb.com>

sparse reports:

  net/psp/psp_nl.c:513:13: sparse: sparse: cast removes address space
  '__rcu' of expression

cmpxchg() returns typeof(*ptr) and its internal casts strip the __rcu
annotation. Wrap it in unrcu_pointer(), the documented way to use an
__rcu pointer with xchg() and friends.

This was introduced by commit 06c2dce2d0f6 ("psp: add new netlink cmd
for dev-assoc and dev-disassoc").

No functional change intended.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202608080910.l9KvOH7O-lkp@intel.com/
Signed-off-by: Wei Wang <weibunny@fb.com>
---
 net/psp/psp_nl.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/psp/psp_nl.c b/net/psp/psp_nl.c
index 43b066353c65..f91665748dde 100644
--- a/net/psp/psp_nl.c
+++ b/net/psp/psp_nl.c
@@ -533,7 +533,8 @@ int psp_nl_dev_assoc_doit(struct sk_buff *skb, struct genl_info *info)
 	}
 
 	/* Check if device is already associated with a PSP device */
-	if (cmpxchg(&assoc_dev->psp_dev, NULL, RCU_INITIALIZER(psd))) {
+	if (unrcu_pointer(cmpxchg(&assoc_dev->psp_dev, NULL,
+				  RCU_INITIALIZER(psd)))) {
 		NL_SET_ERR_MSG(info->extack,
 			       "Device already associated with a PSP device");
 		err = -EBUSY;
-- 
2.53.0-Meta

Re: [PATCH net] psp: use unrcu_pointer() for the cmpxchg() on netdev psp_dev

[Daniel Zahka]

On 8/13/26 3:34 PM, Wei Wang wrote:
> From: Wei Wang <weibunny@fb.com>
> 
> sparse reports:
> 
>    net/psp/psp_nl.c:513:13: sparse: sparse: cast removes address space
>    '__rcu' of expression
> 
> cmpxchg() returns typeof(*ptr) and its internal casts strip the __rcu
> annotation. Wrap it in unrcu_pointer(), the documented way to use an
> __rcu pointer with xchg() and friends.
> 
> This was introduced by commit 06c2dce2d0f6 ("psp: add new netlink cmd
> for dev-assoc and dev-disassoc").
> 
> No functional change intended.
> 
> Reported-by: kernel test robot <lkp@intel.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202608080910.l9KvOH7O-lkp@intel.com/
> Signed-off-by: Wei Wang <weibunny@fb.com>
Commits targeting the net tree need a fixes tag.

Re: [PATCH net] psp: use unrcu_pointer() for the cmpxchg() on netdev psp_dev

[Wei Wang]

On Thu, Aug 13, 2026 at 12:57 PM Daniel Zahka <daniel.zahka@gmail.com> wrote:
>
> >
>
>
> On 8/13/26 3:34 PM, Wei Wang wrote:
> > From: Wei Wang <weibunny@fb.com>
> >
> > sparse reports:
> >
> >    net/psp/psp_nl.c:513:13: sparse: sparse: cast removes address space
> >    '__rcu' of expression
> >
> > cmpxchg() returns typeof(*ptr) and its internal casts strip the __rcu
> > annotation. Wrap it in unrcu_pointer(), the documented way to use an
> > __rcu pointer with xchg() and friends.
> >
> > This was introduced by commit 06c2dce2d0f6 ("psp: add new netlink cmd
> > for dev-assoc and dev-disassoc").
> >
> > No functional change intended.
> >
> > Reported-by: kernel test robot <lkp@intel.com>
> > Closes: https://lore.kernel.org/oe-kbuild-all/202608080910.l9KvOH7O-lkp@intel.com/
> > Signed-off-by: Wei Wang <weibunny@fb.com>
> Commits targeting the net tree need a fixes tag.

This is a sparse warning fix, my understanding is that it's not a
functional fix and therefore should not use a Fixes tag. Please let me
know if my understanding is wrong.