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   1 From: Remi Pommarel <repk@triplefau.lt>
   2 Date: Tue, 24 Sep 2024 21:28:05 +0200
   3 Subject: [PATCH] wifi: mac80211: Convert color collision detection to wiphy
   4  work
   5
   6 Call to ieee80211_color_collision_detection_work() needs wiphy lock to
   7 be held (see lockdep assert in cfg80211_bss_color_notify()). Not locking
   8 wiphy causes the following lockdep error:
   9
  10   WARNING: CPU: 2 PID: 42 at net/wireless/nl80211.c:19505 cfg80211_bss_color_notify+0x1a4/0x25c
  11   Modules linked in:
  12   CPU: 2 PID: 42 Comm: kworker/u8:3 Tainted: G        W          6.4.0-02327-g36c6cb260481 #1048
  13   Hardware name:
  14   Workqueue: phy1 ieee80211_color_collision_detection_work
  15   pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
  16   pc : cfg80211_bss_color_notify+0x1a4/0x25c
  17   lr : cfg80211_bss_color_notify+0x1a0/0x25c
  18   sp : ffff000002947d00
  19   x29: ffff000002947d00 x28: ffff800008e1a000 x27: ffff000002bd4705
  20   x26: ffff00000d034000 x25: ffff80000903cf40 x24: 0000000000000000
  21   x23: ffff00000cb70720 x22: 0000000000800000 x21: ffff800008dfb008
  22   x20: 000000000000008d x19: ffff00000d035fa8 x18: 0000000000000010
  23   x17: 0000000000000001 x16: 000003564b1ce96a x15: 000d69696d057970
  24   x14: 000000000000003b x13: 0000000000000001 x12: 0000000000040000
  25   x11: 0000000000000001 x10: ffff80000978f9c0 x9 : ffff0000028d3174
  26   x8 : ffff800008e30000 x7 : 0000000000000000 x6 : 0000000000000028
  27   x5 : 000000000002f498 x4 : ffff00000d034a80 x3 : 0000000000800000
  28   x2 : ffff800016143000 x1 : 0000000000000000 x0 : 0000000000000000
  29   Call trace:
  30    cfg80211_bss_color_notify+0x1a4/0x25c
  31    ieee80211_color_collision_detection_work+0x20/0x118
  32    process_one_work+0x294/0x554
  33    worker_thread+0x70/0x440
  34    kthread+0xf4/0xf8
  35    ret_from_fork+0x10/0x20
  36   irq event stamp: 77372
  37   hardirqs last  enabled at (77371): [<ffff800008a346fc>] _raw_spin_unlock_irq+0x2c/0x4c
  38   hardirqs last disabled at (77372): [<ffff800008a28754>] el1_dbg+0x20/0x48
  39   softirqs last  enabled at (77350): [<ffff8000089e120c>] batadv_send_outstanding_bcast_packet+0xb8/0x120
  40   softirqs last disabled at (77348): [<ffff8000089e11d4>] batadv_send_outstanding_bcast_packet+0x80/0x120
  41
  42 The wiphy lock cannot be taken directly from color collision detection
  43 delayed work (ieee80211_color_collision_detection_work()) because this
  44 work is cancel_delayed_work_sync() under this wiphy lock causing a
  45 potential deadlock( see [0] for details).
  46
  47 To fix that ieee80211_color_collision_detection_work() could be
  48 converted to a wiphy work and cancel_delayed_work_sync() can be simply
  49 replaced by wiphy_delayed_work_cancel() serving the same purpose under
  50 wiphy lock.
  51
  52 This could potentially fix [1].
  53
  54 [0]: https://lore.kernel.org/linux-wireless/D4A40Q44OAY2.W3SIF6UEPBUN@freebox.fr/
  55 [1]: https://lore.kernel.org/lkml/000000000000612f290618eee3e5@google.com/
  56
  57 Reported-by: Nicolas Escande <nescande@freebox.fr>
  58 Signed-off-by: Remi Pommarel <repk@triplefau.lt>
  59 Link: https://patch.msgid.link/20240924192805.13859-3-repk@triplefau.lt
  60 Signed-off-by: Johannes Berg <johannes.berg@intel.com>
  61 ---
  62
  63 --- a/net/mac80211/cfg.c
  64 +++ b/net/mac80211/cfg.c
  65 @@ -4836,12 +4836,12 @@ void ieee80211_color_change_finalize_wor
  66         ieee80211_color_change_finalize(link);
  67  }
  68
  69 -void ieee80211_color_collision_detection_work(struct work_struct *work)
  70 +void ieee80211_color_collision_detection_work(struct wiphy *wiphy,
  71 +                                             struct wiphy_work *work)
  72  {
  73 -       struct delayed_work *delayed_work = to_delayed_work(work);
  74         struct ieee80211_link_data *link =
  75 -               container_of(delayed_work, struct ieee80211_link_data,
  76 -                            color_collision_detect_work);
  77 +               container_of(work, struct ieee80211_link_data,
  78 +                            color_collision_detect_work.work);
  79         struct ieee80211_sub_if_data *sdata = link->sdata;
  80
  81         cfg80211_obss_color_collision_notify(sdata->dev, link->color_bitmap,
  82 @@ -4894,7 +4894,8 @@ ieee80211_obss_color_collision_notify(st
  83                 return;
  84         }
  85
  86 -       if (delayed_work_pending(&link->color_collision_detect_work)) {
  87 +       if (wiphy_delayed_work_pending(sdata->local->hw.wiphy,
  88 +                                      &link->color_collision_detect_work)) {
  89                 rcu_read_unlock();
  90                 return;
  91         }
  92 @@ -4903,9 +4904,9 @@ ieee80211_obss_color_collision_notify(st
  93         /* queue the color collision detection event every 500 ms in order to
  94          * avoid sending too much netlink messages to userspace.
  95          */
  96 -       ieee80211_queue_delayed_work(&sdata->local->hw,
  97 -                                    &link->color_collision_detect_work,
  98 -                                    msecs_to_jiffies(500));
  99 +       wiphy_delayed_work_queue(sdata->local->hw.wiphy,
 100 +                                &link->color_collision_detect_work,
 101 +                                msecs_to_jiffies(500));
 102
 103         rcu_read_unlock();
 104  }
 105 --- a/net/mac80211/ieee80211_i.h
 106 +++ b/net/mac80211/ieee80211_i.h
 107 @@ -1056,7 +1056,7 @@ struct ieee80211_link_data {
 108         } csa;
 109
 110         struct wiphy_work color_change_finalize_work;
 111 -       struct delayed_work color_collision_detect_work;
 112 +       struct wiphy_delayed_work color_collision_detect_work;
 113         u64 color_bitmap;
 114
 115         /* context reservation -- protected with wiphy mutex */
 116 @@ -2010,7 +2010,8 @@ int ieee80211_channel_switch(struct wiph
 117  /* color change handling */
 118  void ieee80211_color_change_finalize_work(struct wiphy *wiphy,
 119                                           struct wiphy_work *work);
 120 -void ieee80211_color_collision_detection_work(struct work_struct *work);
 121 +void ieee80211_color_collision_detection_work(struct wiphy *wiphy,
 122 +                                             struct wiphy_work *work);
 123
 124  /* interface handling */
 125  #define MAC80211_SUPPORTED_FEATURES_TX (NETIF_F_IP_CSUM | NETIF_F_IPV6_CSUM | \
 126 --- a/net/mac80211/link.c
 127 +++ b/net/mac80211/link.c
 128 @@ -41,8 +41,8 @@ void ieee80211_link_init(struct ieee8021
 129                         ieee80211_csa_finalize_work);
 130         wiphy_work_init(&link->color_change_finalize_work,
 131                         ieee80211_color_change_finalize_work);
 132 -       INIT_DELAYED_WORK(&link->color_collision_detect_work,
 133 -                         ieee80211_color_collision_detection_work);
 134 +       wiphy_delayed_work_init(&link->color_collision_detect_work,
 135 +                               ieee80211_color_collision_detection_work);
 136         INIT_LIST_HEAD(&link->assigned_chanctx_list);
 137         INIT_LIST_HEAD(&link->reserved_chanctx_list);
 138         wiphy_delayed_work_init(&link->dfs_cac_timer_work,
 139 @@ -72,7 +72,8 @@ void ieee80211_link_stop(struct ieee8021
 140         if (link->sdata->vif.type == NL80211_IFTYPE_STATION)
 141                 ieee80211_mgd_stop_link(link);
 142
 143 -       cancel_delayed_work_sync(&link->color_collision_detect_work);
 144 +       wiphy_delayed_work_cancel(link->sdata->local->hw.wiphy,
 145 +                                 &link->color_collision_detect_work);
 146         wiphy_work_cancel(link->sdata->local->hw.wiphy,
 147                           &link->color_change_finalize_work);
 148         wiphy_work_cancel(link->sdata->local->hw.wiphy,