In the case of an empty wakeup_sources list, wakeup_sources_walk_start()
will return an invalid but non-NULL address. This also affects wrappers
of the aforementioned function, like for_each_wakeup_source().

This patch updates wakeup_sources_walk_start() to return NULL in case of
an empty list.

Signed-off-by: Samuel Wu <wusamuel@google.com>
---
 drivers/base/power/wakeup.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/base/power/wakeup.c b/drivers/base/power/wakeup.c
index 1e1a0e7eeac5..e69033d16fba 100644
--- a/drivers/base/power/wakeup.c
+++ b/drivers/base/power/wakeup.c
@@ -275,9 +275,7 @@ EXPORT_SYMBOL_GPL(wakeup_sources_read_unlock);
  */
 struct wakeup_source *wakeup_sources_walk_start(void)
 {
-	struct list_head *ws_head = &wakeup_sources;
-
-	return list_entry_rcu(ws_head->next, struct wakeup_source, entry);
+	return list_first_or_null_rcu(&wakeup_sources, struct wakeup_source, entry);
 }
 EXPORT_SYMBOL_GPL(wakeup_sources_walk_start);
 
-- 
2.52.0.457.g6b5491de43-goog

On Sat, Jan 24, 2026 at 2:22 AM Samuel Wu <wusamuel@google.com> wrote:
>
> In the case of an empty wakeup_sources list, wakeup_sources_walk_start()
> will return an invalid but non-NULL address. This also affects wrappers
> of the aforementioned function, like for_each_wakeup_source().
>
> This patch updates wakeup_sources_walk_start() to return NULL in case of
> an empty list.
>
> Signed-off-by: Samuel Wu <wusamuel@google.com>
> ---
>  drivers/base/power/wakeup.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
>
> diff --git a/drivers/base/power/wakeup.c b/drivers/base/power/wakeup.c
> index 1e1a0e7eeac5..e69033d16fba 100644
> --- a/drivers/base/power/wakeup.c
> +++ b/drivers/base/power/wakeup.c
> @@ -275,9 +275,7 @@ EXPORT_SYMBOL_GPL(wakeup_sources_read_unlock);
>   */
>  struct wakeup_source *wakeup_sources_walk_start(void)
>  {
> -       struct list_head *ws_head = &wakeup_sources;
> -
> -       return list_entry_rcu(ws_head->next, struct wakeup_source, entry);
> +       return list_first_or_null_rcu(&wakeup_sources, struct wakeup_source, entry);
>  }
>  EXPORT_SYMBOL_GPL(wakeup_sources_walk_start);
>
> --

This looks like a fix for the for_each_wakeup_source() users.

I can apply it without the next two patches.

On Tue, Jan 27, 2026 at 8:15 AM Rafael J. Wysocki <rafael@kernel.org> wrote:
>
> On Sat, Jan 24, 2026 at 2:22 AM Samuel Wu <wusamuel@google.com> wrote:
> >
> > In the case of an empty wakeup_sources list, wakeup_sources_walk_start()
> > will return an invalid but non-NULL address. This also affects wrappers
> > of the aforementioned function, like for_each_wakeup_source().
> >
> > This patch updates wakeup_sources_walk_start() to return NULL in case of
> > an empty list.
> >
> > Signed-off-by: Samuel Wu <wusamuel@google.com>
> > ---
> >  drivers/base/power/wakeup.c | 4 +---
> >  1 file changed, 1 insertion(+), 3 deletions(-)
> >
> > diff --git a/drivers/base/power/wakeup.c b/drivers/base/power/wakeup.c
> > index 1e1a0e7eeac5..e69033d16fba 100644
> > --- a/drivers/base/power/wakeup.c
> > +++ b/drivers/base/power/wakeup.c
> > @@ -275,9 +275,7 @@ EXPORT_SYMBOL_GPL(wakeup_sources_read_unlock);
> >   */
> >  struct wakeup_source *wakeup_sources_walk_start(void)
> >  {
> > -       struct list_head *ws_head = &wakeup_sources;
> > -
> > -       return list_entry_rcu(ws_head->next, struct wakeup_source, entry);
> > +       return list_first_or_null_rcu(&wakeup_sources, struct wakeup_source, entry);
> >  }
> >  EXPORT_SYMBOL_GPL(wakeup_sources_walk_start);
> >
> > --
>
> This looks like a fix for the for_each_wakeup_source() users.
>
> I can apply it without the next two patches.

Yes please. Feel free to apply this patch independently, as it can
exist as a standalone fix independent of the subsequent two patches in
the series.

Thanks!

On Mon, Feb 2, 2026 at 9:23 PM Samuel Wu <wusamuel@google.com> wrote:
>
> On Tue, Jan 27, 2026 at 8:15 AM Rafael J. Wysocki <rafael@kernel.org> wrote:
> >
> > On Sat, Jan 24, 2026 at 2:22 AM Samuel Wu <wusamuel@google.com> wrote:
> > >
> > > In the case of an empty wakeup_sources list, wakeup_sources_walk_start()
> > > will return an invalid but non-NULL address. This also affects wrappers
> > > of the aforementioned function, like for_each_wakeup_source().
> > >
> > > This patch updates wakeup_sources_walk_start() to return NULL in case of
> > > an empty list.
> > >
> > > Signed-off-by: Samuel Wu <wusamuel@google.com>
> > > ---
> > >  drivers/base/power/wakeup.c | 4 +---
> > >  1 file changed, 1 insertion(+), 3 deletions(-)
> > >
> > > diff --git a/drivers/base/power/wakeup.c b/drivers/base/power/wakeup.c
> > > index 1e1a0e7eeac5..e69033d16fba 100644
> > > --- a/drivers/base/power/wakeup.c
> > > +++ b/drivers/base/power/wakeup.c
> > > @@ -275,9 +275,7 @@ EXPORT_SYMBOL_GPL(wakeup_sources_read_unlock);
> > >   */
> > >  struct wakeup_source *wakeup_sources_walk_start(void)
> > >  {
> > > -       struct list_head *ws_head = &wakeup_sources;
> > > -
> > > -       return list_entry_rcu(ws_head->next, struct wakeup_source, entry);
> > > +       return list_first_or_null_rcu(&wakeup_sources, struct wakeup_source, entry);
> > >  }
> > >  EXPORT_SYMBOL_GPL(wakeup_sources_walk_start);
> > >
> > > --
> >
> > This looks like a fix for the for_each_wakeup_source() users.
> >
> > I can apply it without the next two patches.
>
> Yes please. Feel free to apply this patch independently, as it can
> exist as a standalone fix independent of the subsequent two patches in
> the series.

OK, applied as 6.20/7.0 material, thanks!