RE: [Intel-wired-lan] [PATCH net-next v2 02/13] wifi: cfg80211: use __rtnl_unlock in nl80211_pre_doit

Loktionov, Aleksandr
2026-03-18T15:41:41Z

> -----Original Message-----
> From: Intel-wired-lan <intel-wired-lan-bounces@osuosl.org> On Behalf
> Of Stanislav Fomichev
> Sent: Wednesday, March 18, 2026 4:03 PM
> To: netdev@vger.kernel.org
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> L <anthony.l.nguyen@intel.com>; Kitszel, Przemyslaw
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> Subject: [Intel-wired-lan] [PATCH net-next v2 02/13] wifi: cfg80211:
> use __rtnl_unlock in nl80211_pre_doit
>
> nl80211_pre_doit acquires rtnl_lock and then wiphy_lock, releasing
> rtnl while keeping wiphy_lock held until post_doit. With the
> introduction of rx_mode_wq and its flush in netdev_run_todo, calling
> rtnl_unlock here creates a circular lock dependency:
>
> Chain exists of:
> (wq_completion)rx_mode_wq --> rtnl_mutex --> &rdev->wiphy.mtx
>
> Possible unsafe locking scenario:
>
> CPU0 CPU1
> ---- ----
> lock(&rdev->wiphy.mtx);
> lock(rtnl_mutex);
> lock(&rdev->wiphy.mtx);
> lock((wq_completion)rx_mode_wq);
>
> Switch to __rtnl_unlock to skip netdev_run_todo in nl80211_pre_doit.
> This seems safe because we run before the op.
>
> Link:
> http://lore.kernel.org/netdev/69b5ad67.a00a0220.3b25d1.001a.GAE@google
> .com
> Signed-off-by: Stanislav Fomichev <sdf@fomichev.me>
> ---
> net/wireless/nl80211.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c index
> 2225f5d0b124..ce5f25d4c87e 100644
> --- a/net/wireless/nl80211.c
> +++ b/net/wireless/nl80211.c
> @@ -18192,7 +18192,7 @@ static int nl80211_pre_doit(const struct
> genl_split_ops *ops,
> __release(&rdev->wiphy.mtx);
> }
> if (!(internal_flags & NL80211_FLAG_NEED_RTNL))
> - rtnl_unlock();
> + __rtnl_unlock();
>
> return 0;
> out_unlock:
> --
> 2.53.0

Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>