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wifi: mt76: mt7921: fix lock inversion between dev->mutex and iflist_mtx

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mt7921_config() holds dev->mutex across
ieee80211_iterate_active_interfaces(), which takes local->iflist_mtx.
mac80211 uses the opposite order: ieee80211_del_virtual_monitor() holds
iflist_mtx while calling drv_unassign_vif_chanctx(), and
mt792x_unassign_vif_chanctx() takes dev->mutex.

Deleting a monitor interface that has a channel assigned reaches the
second order and lockdep reports the cycle. The driver side of it:

  -> #1 (&local->iflist_mtx){+.+.}-{4:4}:
         __mutex_lock+0xda/0x1070
         ieee80211_iterate_interfaces+0x34/0x70 [mac80211]
         mt7921_config+0xb8/0xe0 [mt7921_common]
         drv_config+0x63/0x1d0 [mac80211]

.config is only reached through drv_config(), which asserts the wiphy
mutex, so ieee80211_iterate_active_interfaces_mtx() can be used. It walks
the same list under the wiphy mutex and never takes iflist_mtx, which
drops the driver's dev->mutex -> iflist_mtx edge.

Fixes: cbaa0a404f8d ("mt76: mt7921: fix up the monitor mode")
Link: https://lore.kernel.org/linux-wireless/[email protected]/
Signed-off-by: Devin Wittmayer <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Felix Fietkau <[email protected]>
This commit is contained in:
Devin Wittmayer
2026-08-27 18:53:31 +02:00
committed by Felix Fietkau
parent e1f87cf2cf
commit 5d68813ec0
1 changed files with 3 additions and 3 deletions
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mt7921/main.c
+1 -1
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@@ -652,7 +652,7 @@ static int mt7921_config(struct ieee80211_hw *hw, int radio_idx, u32 changed)
}
if (changed & IEEE80211_CONF_CHANGE_MONITOR) {
ieee80211_iterate_active_interfaces(hw,
ieee80211_iterate_active_interfaces_mtx(hw,
IEEE80211_IFACE_ITER_RESUME_ALL,
mt7921_sniffer_interface_iter, dev);
}