firewire: core: extend card->lock in fw_core_handle_bus_reset

card->local_node and card->bm_retries are both always accessed under
card->lock.
fw_core_handle_bus_reset has a check whose condition depends on
card->local_node and whose body writes to card->bm_retries.
Both of these accesses are not under card->lock. Move the lock acquiring
of card->lock to before this check such that these accesses do happen
when card->lock is held.
fw_destroy_nodes is called inside the check.
Since fw_destroy_nodes already acquires card->lock inside its function
body, move this out to the callsites of fw_destroy_nodes.
Also add a comment to indicate which locking is necessary when calling
fw_destroy_nodes.

Cc: <stable@vger.kernel.org>
Signed-off-by: Niels Dossche <dossche.niels@gmail.com>
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Link: https://lore.kernel.org/r/20220409041243.603210-4-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Iwai <tiwai@suse.de>

Author: ndossche

drivers/firewire/core-card.c

@@ -668,6 +668,7 @@ EXPORT_SYMBOL_GPL(fw_card_release);
 void fw_core_remove_card(struct fw_card *card)
 {
 	struct fw_card_driver dummy_driver = dummy_driver_template;
+	unsigned long flags;
 
 	card->driver->update_phy_reg(card, 4,
 				     PHY_LINK_ACTIVE | PHY_CONTENDER, 0);
@@ -682,7 +683,9 @@ void fw_core_remove_card(struct fw_card *card)
 	dummy_driver.stop_iso		= card->driver->stop_iso;
 	card->driver = &dummy_driver;
 
+	spin_lock_irqsave(&card->lock, flags);
 	fw_destroy_nodes(card);
+	spin_unlock_irqrestore(&card->lock, flags);
 
 	/* Wait for all users, especially device workqueue jobs, to finish. */
 	fw_card_put(card);

drivers/firewire/core-topology.c

@@ -375,16 +375,13 @@ static void report_found_node(struct fw_card *card,
 	card->bm_retries = 0;
 }
 
+/* Must be called with card->lock held */
 void fw_destroy_nodes(struct fw_card *card)
 {
-	unsigned long flags;
-
-	spin_lock_irqsave(&card->lock, flags);
 	card->color++;
 	if (card->local_node != NULL)
 		for_each_fw_node(card, card->local_node, report_lost_node);
 	card->local_node = NULL;
-	spin_unlock_irqrestore(&card->lock, flags);
 }
 
 static void move_tree(struct fw_node *node0, struct fw_node *node1, int port)
@@ -510,6 +507,8 @@ void fw_core_handle_bus_reset(struct fw_card *card, int node_id, int generation,
 	struct fw_node *local_node;
 	unsigned long flags;
 
+	spin_lock_irqsave(&card->lock, flags);
+
 	/*
 	 * If the selfID buffer is not the immediate successor of the
 	 * previously processed one, we cannot reliably compare the
@@ -521,8 +520,6 @@ void fw_core_handle_bus_reset(struct fw_card *card, int node_id, int generation,
 		card->bm_retries = 0;
 	}
 
-	spin_lock_irqsave(&card->lock, flags);
-
 	card->broadcast_channel_allocated = card->broadcast_channel_auto_allocated;
 	card->node_id = node_id;
 	/*