linux-kernel - Re: [PATCH v3] wifi: iwlegacy: 3945-rs: add a defensive WARN_ON_ONCE for il_sta in il3945_rs_get

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Message-ID: <CADm8Tenw9kpk9suABMEYguURxtWrXRaRAiXogxUfwSash-c0ng@mail.gmail.com>
Date: Fri, 9 Jan 2026 23:12:55 +0800
From: Tuo Li <islituo@...il.com>
To: Stanislaw Gruszka <stf_xl@...pl>
Cc: linux-wireless@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] wifi: iwlegacy: 3945-rs: add a defensive WARN_ON_ONCE
 for il_sta in il3945_rs_get_rate()

Hi Stanislaw,

On Fri, Jan 9, 2026 at 5:02 PM Stanislaw Gruszka <stf_xl@...pl> wrote:
>
> Hi Tuo,
>
> On Fri, Jan 09, 2026 at 11:40:14AM +0800, Tuo Li wrote:
> > In this function, il_sta is not expected to be NULL. Add a defensive
> > WARN_ON_ONCE() to catch this unexpected condition and aid debugging.
> >
> > Signed-off-by: Tuo Li <islituo@...il.com>
> > ---
> > v3:
> > * Replace plain NULL check with WARN_ON_ONCE() and update subject to better
> >   reflect defensive nature of the check.
> >   Thanks to Johannes Berg and Stanislaw Gruszka for helpful advice.
> > v2:
> > * Return early for uninitialized STA il data and align D_RATE messages with
> >   il3945_rs_tx_status(). Add a wifi: prefix to the patch title.
> >   Thanks to Stanislaw Gruszka for the helpful advice.
> > ---
> >  drivers/net/wireless/intel/iwlegacy/3945-rs.c | 3 +++
> >  1 file changed, 3 insertions(+)
> >
> > diff --git a/drivers/net/wireless/intel/iwlegacy/3945-rs.c b/drivers/net/wireless/intel/iwlegacy/3945-rs.c
> > index 1826c37c090c..463565ce14af 100644
> > --- a/drivers/net/wireless/intel/iwlegacy/3945-rs.c
> > +++ b/drivers/net/wireless/intel/iwlegacy/3945-rs.c
> > @@ -626,6 +626,9 @@ il3945_rs_get_rate(void *il_r, struct ieee80211_sta *sta, void *il_sta,
> >
> >       D_RATE("enter\n");
> >
> > +     if (WARN_ON_ONCE(!il_sta))
> > +             return;
> > +
>
> Sorry for giving you wrong advice before, but after examining related code
> I agree with Johannes the il_sta can not be NULL.
> Now, I think we should just remove il_sta/rs_sta pointer check.
>
> Regards
> Stanislaw

Thanks for the follow-up and your patience. I appreciate you taking
another look at the code.

Just to confirm, would you like me to submit a v4 patch that removes the
unnecessary il_sta / rs_sta checks, e.g.:

in il3945_rs_get_rate():

- if (rs_sta && !rs_sta->il) {
+ if (!rs_sta->il) {

and in il3945_rs_tx_status():

- if (!il_sta) {
-     D_RATE("leave: No STA il data to update!\n");
-     return;
- }

If a v4 is not needed, I'm also fine with dropping this patch series.

Best regards,
Tuo