staging: rtl8192u: Fix sleep in atomic context bug in dm_fsync_timer_callback

There are sleep in atomic context bugs when dm_fsync_timer_callback is
executing. The root cause is that the memory allocation functions with
GFP_KERNEL or GFP_NOIO parameters are called in dm_fsync_timer_callback
which is a timer handler. The call paths that could trigger bugs are
shown below:

    (interrupt context)
dm_fsync_timer_callback
  write_nic_byte
    kzalloc(sizeof(data), GFP_KERNEL); //may sleep
    usb_control_msg
      kmalloc(.., GFP_NOIO); //may sleep
  write_nic_dword
    kzalloc(sizeof(data), GFP_KERNEL); //may sleep
    usb_control_msg
      kmalloc(.., GFP_NOIO); //may sleep

This patch uses delayed work to replace timer and moves the operations
that may sleep into the delayed work in order to mitigate bugs.

Fixes: 8fc8598e ("Staging: Added Realtek rtl8192u driver to staging")
Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
Link: https://lore.kernel.org/r/20220710103002.63283-1-duoming@zju.edu.cnSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8192u/r8192U.h

@@ -1013,7 +1013,7 @@ typedef struct r8192_priv {
 	bool		bis_any_nonbepkts;
 	bool		bcurrent_turbo_EDCA;
 	bool		bis_cur_rdlstate;
-	struct timer_list fsync_timer;
+	struct delayed_work fsync_work;
 	bool bfsync_processing;	/* 500ms Fsync timer is active or not */
 	u32	rate_record;
 	u32	rateCountDiffRecord;

drivers/staging/rtl8192u/r8192U_dm.c

@@ -2578,19 +2578,20 @@ static void dm_init_fsync(struct net_device *dev)
 	priv->ieee80211->fsync_seconddiff_ratethreshold = 200;
 	priv->ieee80211->fsync_state = Default_Fsync;
 	priv->framesyncMonitor = 1;	/* current default 0xc38 monitor on */
-	timer_setup(&priv->fsync_timer, dm_fsync_timer_callback, 0);
+	INIT_DELAYED_WORK(&priv->fsync_work, dm_fsync_work_callback);
 }
 
 static void dm_deInit_fsync(struct net_device *dev)
 {
 	struct r8192_priv *priv = ieee80211_priv(dev);
 
-	del_timer_sync(&priv->fsync_timer);
+	cancel_delayed_work_sync(&priv->fsync_work);
 }
 
-void dm_fsync_timer_callback(struct timer_list *t)
+void dm_fsync_work_callback(struct work_struct *work)
 {
-	struct r8192_priv *priv = from_timer(priv, t, fsync_timer);
+	struct r8192_priv *priv =
+	    container_of(work, struct r8192_priv, fsync_work.work);
 	struct net_device *dev = priv->ieee80211->dev;
 	u32 rate_index, rate_count = 0, rate_count_diff = 0;
 	bool		bSwitchFromCountDiff = false;
@@ -2657,17 +2658,16 @@ void dm_fsync_timer_callback(struct timer_list *t)
 			}
 		}
 		if (bDoubleTimeInterval) {
-			if (timer_pending(&priv->fsync_timer))
-				del_timer_sync(&priv->fsync_timer);
-			priv->fsync_timer.expires = jiffies +
-				msecs_to_jiffies(priv->ieee80211->fsync_time_interval*priv->ieee80211->fsync_multiple_timeinterval);
-			add_timer(&priv->fsync_timer);
+			cancel_delayed_work_sync(&priv->fsync_work);
+			schedule_delayed_work(&priv->fsync_work,
+					      msecs_to_jiffies(priv
+					      ->ieee80211->fsync_time_interval *
+					      priv->ieee80211->fsync_multiple_timeinterval));
 		} else {
-			if (timer_pending(&priv->fsync_timer))
-				del_timer_sync(&priv->fsync_timer);
-			priv->fsync_timer.expires = jiffies +
-				msecs_to_jiffies(priv->ieee80211->fsync_time_interval);
-			add_timer(&priv->fsync_timer);
+			cancel_delayed_work_sync(&priv->fsync_work);
+			schedule_delayed_work(&priv->fsync_work,
+					      msecs_to_jiffies(priv
+					      ->ieee80211->fsync_time_interval));
 		}
 	} else {
 		/* Let Register return to default value; */
@@ -2695,7 +2695,7 @@ static void dm_EndSWFsync(struct net_device *dev)
 	struct r8192_priv *priv = ieee80211_priv(dev);
 
 	RT_TRACE(COMP_HALDM, "%s\n", __func__);
-	del_timer_sync(&(priv->fsync_timer));
+	cancel_delayed_work_sync(&priv->fsync_work);
 
 	/* Let Register return to default value; */
 	if (priv->bswitch_fsync) {
@@ -2736,11 +2736,9 @@ static void dm_StartSWFsync(struct net_device *dev)
 		if (priv->ieee80211->fsync_rate_bitmap &  rateBitmap)
 			priv->rate_record += priv->stats.received_rate_histogram[1][rateIndex];
 	}
-	if (timer_pending(&priv->fsync_timer))
-		del_timer_sync(&priv->fsync_timer);
-	priv->fsync_timer.expires = jiffies +
-			msecs_to_jiffies(priv->ieee80211->fsync_time_interval);
-	add_timer(&priv->fsync_timer);
+	cancel_delayed_work_sync(&priv->fsync_work);
+	schedule_delayed_work(&priv->fsync_work,
+			      msecs_to_jiffies(priv->ieee80211->fsync_time_interval));
 
 	write_nic_dword(dev, rOFDM0_RxDetector2, 0x465c12cd);
 }

drivers/staging/rtl8192u/r8192U_dm.h

@@ -166,7 +166,7 @@ void dm_force_tx_fw_info(struct net_device *dev,
 void dm_init_edca_turbo(struct net_device *dev);
 void dm_rf_operation_test_callback(unsigned long data);
 void dm_rf_pathcheck_workitemcallback(struct work_struct *work);
-void dm_fsync_timer_callback(struct timer_list *t);
+void dm_fsync_work_callback(struct work_struct *work);
 void dm_cck_txpower_adjust(struct net_device *dev, bool  binch14);
 void dm_shadow_init(struct net_device *dev);
 void dm_initialize_txpower_tracking(struct net_device *dev);