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

[syzbot <syzbot+bd5829ba3619f08e2341@syzkaller.appspotmail.com>]

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Subject: Re: [PATCH RFC v2] wifi: cfg80211: replace WARN_ON() with dev_err() in netns switch
Author: nogikh@google.com

Debugging went 100% astray because of an strace output in the repro run results.

#syz reject

On Tue, May 19, 2026 at 12:08 AM 'syzbot' via
syzkaller-upstream-moderation
<syzkaller-upstream-moderation@googlegroups.com> 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@syzkaller.appspotmail.com
> Link: https://syzkaller.appspot.com/bug?extid=bd5829ba3619f08e2341
> Link: https://syzkaller.appspot.com/ai_job?id=a1cfc84c-7c0f-4340-891d-885fcee80cad
> To: <alex.aring@gmail.com>
> To: <davem@davemloft.net>
> To: <edumazet@google.com>
> To: <kuba@kernel.org>
> To: <linux-wpan@vger.kernel.org>
> To: <miquel.raynal@bootlin.com>
> To: <netdev@vger.kernel.org>
> To: <pabeni@redhat.com>
> To: <stefan@datenfreihafen.org>
> Cc: <horms@kernel.org>
> Cc: <johannes@sipsolutions.net>
> Cc: <linux-kernel@vger.kernel.org>
> Cc: <linux-wireless@vger.kernel.org>
>
> ---
> 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@mail.kernel.org/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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