Re: Forwarded: Re: [PATCH RFC v2] wifi: cfg80211: replace WARN_ON() with dev_err() in netns switch

[Dmitry Vyukov]

On Tue, 19 May 2026 at 16:08, syzbot
<syzbot+bd5829ba3619f08e2341@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> For archival purposes, forwarding an incoming command email to
> linux-kernel@xxxxxxxxxxxxxxx, syzkaller-bugs@xxxxxxxxxxxxxxxx.
>
> ***
>
> Subject: Re: [PATCH RFC v2] wifi: cfg80211: replace WARN_ON() with dev_err() in netns switch
> Author: nogikh@xxxxxxxxxx
>
> Debugging went 100% astray because of an strace output in the repro run results.

The "100% astray" was related to the "WARNING: ODEBUG bug in
ieee80211_led_exit (2)" bug, not this one.

> #syz reject
>
> On Tue, May 19, 2026 at 12:08 AM 'syzbot' via
> syzkaller-upstream-moderation
> <syzkaller-upstream-moderation@xxxxxxxxxxxxxxxx> wrote:
> >
> > The syzkaller reported a kernel panic in cfg802154_switch_netns() when
> > device_rename() fails with -ENOMEM. The crash occurs because WARN_ON()
> > is used to handle the memory allocation failure, which escalates into a
> > kernel panic when panic_on_warn is enabled.
> >
> > Memory allocation failures are expected runtime events under memory
> > pressure and should be handled gracefully. The WARN_ON() macro must not
> > be used for conditions that can legitimately happen. Failing to rename
> > the device or change the network namespace is not a fatal system error.
> >
> > Replace the WARN_ON() calls with dev_err() in both
> > cfg802154_switch_netns() and cfg80211_switch_netns(), as well as in
> > their respective pernet exit handlers (cfg802154_pernet_exit() and
> > cfg80211_pernet_exit()). This ensures that memory allocation failures
> > under pressure are handled gracefully, logging the error for debugging
> > purposes without bringing down the entire system.
> >
> > Fixes: 04600794958f1833f5571c6cde40f260ab557f55 ("cfg80211: support sysfs namespaces")
> > Assisted-by: Gemini:gemini-3.1-pro-preview Gemini:gemini-3-flash-preview
> > Reported-by: syzbot+bd5829ba3619f08e2341@xxxxxxxxxxxxxxxxxxxxxxxxx
> > Link: https://syzkaller.appspot.com/bug?extid=bd5829ba3619f08e2341
> > Link: https://syzkaller.appspot.com/ai_job?id=a1cfc84c-7c0f-4340-891d-885fcee80cad
> > To: <alex.aring@xxxxxxxxx>
> > To: <davem@xxxxxxxxxxxxx>
> > To: <edumazet@xxxxxxxxxx>
> > To: <kuba@xxxxxxxxxx>
> > To: <linux-wpan@xxxxxxxxxxxxxxx>
> > To: <miquel.raynal@xxxxxxxxxxx>
> > To: <netdev@xxxxxxxxxxxxxxx>
> > To: <pabeni@xxxxxxxxxx>
> > To: <stefan@xxxxxxxxxxxxxxxxxx>
> > Cc: <horms@xxxxxxxxxx>
> > Cc: <johannes@xxxxxxxxxxxxxxxx>
> > Cc: <linux-kernel@xxxxxxxxxxxxxxx>
> > Cc: <linux-wireless@xxxxxxxxxxxxxxx>
> >
> > ---
> > v2:
> > - Replaced pr_err() with dev_err() to include device details in the error messages.
> >
> > v1:
> > https://lore.kernel.org/all/7d949fbc-9781-4428-bfac-e51501b18bf7@xxxxxxxxxxxxxxx/T/
> > ---
> > diff --git a/net/ieee802154/core.c b/net/ieee802154/core.c
> > index 89b671b12..07082857c 100644
> > --- a/net/ieee802154/core.c
> > +++ b/net/ieee802154/core.c
> > @@ -245,7 +245,9 @@ int cfg802154_switch_netns(struct cfg802154_registered_device *rdev,
> >                         wpan_dev->netdev->netns_immutable = false;
> >                         err = dev_change_net_namespace(wpan_dev->netdev, net,
> >                                                        "wpan%d");
> > -                       WARN_ON(err);
> > +                       if (err)
> > +                               dev_err(&rdev->wpan_phy.dev,
> > +                                       "failed to change netns: %d\n", err);
> >                         wpan_dev->netdev->netns_immutable = true;
> >                 }
> >
> > @@ -255,7 +257,9 @@ int cfg802154_switch_netns(struct cfg802154_registered_device *rdev,
> >         wpan_phy_net_set(&rdev->wpan_phy, net);
> >
> >         err = device_rename(&rdev->wpan_phy.dev, dev_name(&rdev->wpan_phy.dev));
> > -       WARN_ON(err);
> > +       if (err)
> > +               dev_err(&rdev->wpan_phy.dev, "failed to rename device: %d\n",
> > +                       err);
> >
> >         return 0;
> >  }
> > @@ -350,8 +354,11 @@ static void __net_exit cfg802154_pernet_exit(struct net *net)
> >
> >         rtnl_lock();
> >         list_for_each_entry(rdev, &cfg802154_rdev_list, list) {
> > -               if (net_eq(wpan_phy_net(&rdev->wpan_phy), net))
> > -                       WARN_ON(cfg802154_switch_netns(rdev, &init_net));
> > +               if (net_eq(wpan_phy_net(&rdev->wpan_phy), net)) {
> > +                       if (cfg802154_switch_netns(rdev, &init_net))
> > +                               dev_err(&rdev->wpan_phy.dev,
> > +                                       "failed to switch netns on exit\n");
> > +               }
> >         }
> >         rtnl_unlock();
> >  }
> > diff --git a/net/wireless/core.c b/net/wireless/core.c
> > index 6783e0672..6badcec46 100644
> > --- a/net/wireless/core.c
> > +++ b/net/wireless/core.c
> > @@ -184,7 +184,9 @@ int cfg80211_switch_netns(struct cfg80211_registered_device *rdev,
> >                         wdev->netdev->netns_immutable = false;
> >                         err = dev_change_net_namespace(wdev->netdev, net,
> >                                                         "wlan%d");
> > -                       WARN_ON(err);
> > +                       if (err)
> > +                               dev_err(&rdev->wiphy.dev,
> > +                                       "failed to change netns: %d\n", err);
> >                         wdev->netdev->netns_immutable = true;
> >                 }
> >
> > @@ -204,7 +206,8 @@ int cfg80211_switch_netns(struct cfg80211_registered_device *rdev,
> >         wiphy_net_set(&rdev->wiphy, net);
> >
> >         err = device_rename(&rdev->wiphy.dev, dev_name(&rdev->wiphy.dev));
> > -       WARN_ON(err);
> > +       if (err)
> > +               dev_err(&rdev->wiphy.dev, "failed to rename device: %d\n", err);
> >
> >         nl80211_notify_wiphy(rdev, NL80211_CMD_NEW_WIPHY);
> >
> > @@ -1809,8 +1812,11 @@ static void __net_exit cfg80211_pernet_exit(struct net *net)
> >
> >         rtnl_lock();
> >         for_each_rdev(rdev) {
> > -               if (net_eq(wiphy_net(&rdev->wiphy), net))
> > -                       WARN_ON(cfg80211_switch_netns(rdev, &init_net));
> > +               if (net_eq(wiphy_net(&rdev->wiphy), net)) {
> > +                       if (cfg80211_switch_netns(rdev, &init_net))
> > +                               dev_err(&rdev->wiphy.dev,
> > +                                       "failed to switch netns on exit\n");
> > +               }
> >         }
> >         rtnl_unlock();
> >  }
> >
> >
> > base-commit: 5d6919055dec134de3c40167a490f33c74c12581
> > --
> > This is an AI-generated patch subject to moderation.
> > Reply with '#syz upstream' to send it to the mailing list.
> > Reply with '#syz reject' to reject it.
> >
> > See  for more information.
> >
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