[PATCH wireless] wifi: cfg80211: convert pmsr_free_wk to wiphy_work to fix deadlock

[Peddolla Harshavardhan Reddy <peddolla.reddy@oss.qualcomm.com>]

When a netlink socket that owns a PMSR session is closed,
cfg80211_release_pmsr() clears the request's nl_portid and queues
pmsr_free_wk to call cfg80211_pmsr_process_abort() asynchronously.

If the interface tears down concurrently, cfg80211_pmsr_wdev_down()
is called under wiphy_lock and calls cancel_work_sync(&pmsr_free_wk)
to wait for any running work. The work function acquires wiphy_lock
via guard(wiphy) before calling process_abort.

This is a deadlock: wdev_down holds wiphy_lock and blocks inside
cancel_work_sync(); pmsr_free_wk blocks trying to acquire that same
wiphy_lock. Neither thread can proceed.

The same deadlock is reachable from cfg80211_leave_locked(), which
calls cfg80211_pmsr_wdev_down() for all interface types under
wiphy_lock.

Fix this by converting pmsr_free_wk from a plain work_struct to a
wiphy_work. The wiphy_work dispatcher holds wiphy_lock when running
work items, so the explicit guard(wiphy) in the work function is no
longer needed. wiphy_work_cancel() can be called safely while holding
wiphy_lock - since wiphy_lock prevents the work from running
concurrently, wiphy_work_cancel() never blocks, eliminating the
deadlock.

Remove the cancel_work_sync() for pmsr_free_wk from the
NETDEV_GOING_DOWN handler. cfg80211_leave(), called unconditionally
just before it, already cancels any pending work under wiphy_lock
via wiphy_work_cancel() inside cfg80211_pmsr_wdev_down().

Fixes: 6dccbc9f3e1d ("wifi: cfg80211: cancel pmsr_free_wk in cfg80211_pmsr_wdev_down")
Signed-off-by: Peddolla Harshavardhan Reddy <peddolla.reddy@oss.qualcomm.com>
---
 include/net/cfg80211.h | 2 +-
 net/wireless/core.c    | 3 +--
 net/wireless/core.h    | 2 +-
 net/wireless/pmsr.c    | 8 +++-----
 4 files changed, 6 insertions(+), 9 deletions(-)

diff --git a/include/net/cfg80211.h b/include/net/cfg80211.h
index 8188ad200de5..3751a1d74765 100644
--- a/include/net/cfg80211.h
+++ b/include/net/cfg80211.h
@@ -7265,7 +7265,7 @@ struct wireless_dev {
 
 	struct list_head pmsr_list;
 	spinlock_t pmsr_lock;
-	struct work_struct pmsr_free_wk;
+	struct wiphy_work pmsr_free_wk;
 
 	unsigned long unprot_beacon_reported;
 
diff --git a/net/wireless/core.c b/net/wireless/core.c
index 3dcf63b04c41..b6bb25ee89cd 100644
--- a/net/wireless/core.c
+++ b/net/wireless/core.c
@@ -1613,7 +1613,7 @@ void cfg80211_init_wdev(struct wireless_dev *wdev)
 	INIT_LIST_HEAD(&wdev->mgmt_registrations);
 	INIT_LIST_HEAD(&wdev->pmsr_list);
 	spin_lock_init(&wdev->pmsr_lock);
-	INIT_WORK(&wdev->pmsr_free_wk, cfg80211_pmsr_free_wk);
+	wiphy_work_init(&wdev->pmsr_free_wk, cfg80211_pmsr_free_wk);
 
 #ifdef CONFIG_CFG80211_WEXT
 	wdev->wext.default_key = -1;
@@ -1747,7 +1747,6 @@ static int cfg80211_netdev_notifier_call(struct notifier_block *nb,
 			cfg80211_remove_links(wdev);
 		/* since we just did cfg80211_leave() nothing to do there */
 		cancel_work_sync(&wdev->disconnect_wk);
-		cancel_work_sync(&wdev->pmsr_free_wk);
 		break;
 	case NETDEV_DOWN:
 		wiphy_lock(&rdev->wiphy);
diff --git a/net/wireless/core.h b/net/wireless/core.h
index df47ed6208a5..f60c66b88677 100644
--- a/net/wireless/core.h
+++ b/net/wireless/core.h
@@ -586,7 +586,7 @@ cfg80211_get_6ghz_power_type(const u8 *elems, size_t elems_len,
 
 void cfg80211_release_pmsr(struct wireless_dev *wdev, u32 portid);
 void cfg80211_pmsr_wdev_down(struct wireless_dev *wdev);
-void cfg80211_pmsr_free_wk(struct work_struct *work);
+void cfg80211_pmsr_free_wk(struct wiphy *wiphy, struct wiphy_work *work);
 
 void cfg80211_remove_link(struct wireless_dev *wdev, unsigned int link_id);
 void cfg80211_remove_links(struct wireless_dev *wdev);
diff --git a/net/wireless/pmsr.c b/net/wireless/pmsr.c
index c8447448f3a5..2c8db33d9c30 100644
--- a/net/wireless/pmsr.c
+++ b/net/wireless/pmsr.c
@@ -807,13 +807,11 @@ static void cfg80211_pmsr_process_abort(struct wireless_dev *wdev)
 	}
 }
 
-void cfg80211_pmsr_free_wk(struct work_struct *work)
+void cfg80211_pmsr_free_wk(struct wiphy *wiphy, struct wiphy_work *work)
 {
 	struct wireless_dev *wdev = container_of(work, struct wireless_dev,
 						 pmsr_free_wk);
 
-	guard(wiphy)(wdev->wiphy);
-
 	cfg80211_pmsr_process_abort(wdev);
 }
 
@@ -829,7 +827,7 @@ void cfg80211_pmsr_wdev_down(struct wireless_dev *wdev)
 	}
 	spin_unlock_bh(&wdev->pmsr_lock);
 
-	cancel_work_sync(&wdev->pmsr_free_wk);
+	wiphy_work_cancel(wdev->wiphy, &wdev->pmsr_free_wk);
 	if (found)
 		cfg80211_pmsr_process_abort(wdev);
 
@@ -844,7 +842,7 @@ void cfg80211_release_pmsr(struct wireless_dev *wdev, u32 portid)
 	list_for_each_entry(req, &wdev->pmsr_list, list) {
 		if (req->nl_portid == portid) {
 			req->nl_portid = 0;
-			schedule_work(&wdev->pmsr_free_wk);
+			wiphy_work_queue(wdev->wiphy, &wdev->pmsr_free_wk);
 		}
 	}
 	spin_unlock_bh(&wdev->pmsr_lock);

base-commit: dc59e4fea9d83f03bad6bddf3fa2e52491777482
-- 
2.34.1