firewire: potentially invalid pointers used in fw_card_bm_work

The bus management workqueue job was in danger to dereference NULL
pointers.  Also, after having temporarily lifted card->lock, a few node
pointers and a device pointer may have become invalid.

Add NULL pointer checks and get the necessary references.  Also, move
card->local_node out of fw_card_bm_work's sight during shutdown of the
card.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Signed-off-by: Jarod Wilson <jwilson@redhat.com>

2 files changed, 35 insertions, 17 deletions

diff --git a/drivers/firewire/fw-card.c b/drivers/firewire/fw-card.c
index 3e9719948a8..e6395b29850 100644
--- a/drivers/firewire/fw-card.c
+++ b/drivers/firewire/fw-card.c
@@ -214,17 +214,29 @@ static void
 fw_card_bm_work(struct work_struct *work)
 {
         struct fw_card *card = container_of(work, struct fw_card, work.work);
-        struct fw_device *root;
+        struct fw_device *root_device;
+        struct fw_node *root_node, *local_node;
         struct bm_data bmd;
         unsigned long flags;
         int root_id, new_root_id, irm_id, gap_count, generation, grace;
         int do_reset = 0;
 
         spin_lock_irqsave(&card->lock, flags);
+        local_node = card->local_node;
+        root_node  = card->root_node;
+
+        if (local_node == NULL) {
+                spin_unlock_irqrestore(&card->lock, flags);
+                return;
+        }
+        fw_node_get(local_node);
+        fw_node_get(root_node);
 
         generation = card->generation;
-        root = card->root_node->data;
-        root_id = card->root_node->node_id;
+        root_device = root_node->data;
+        if (root_device)
+                fw_device_get(root_device);
+        root_id = root_node->node_id;
         grace = time_after(jiffies, card->reset_jiffies + DIV_ROUND_UP(HZ, 10));
 
         if (card->bm_generation + 1 == generation ||
@@ -243,14 +255,14 @@ fw_card_bm_work(struct work_struct *work)
 
                 irm_id = card->irm_node->node_id;
                 if (!card->irm_node->link_on) {
-                        new_root_id = card->local_node->node_id;
+                        new_root_id = local_node->node_id;
                         fw_notify("IRM has link off, making local node (%02x) root.\n",
                                   new_root_id);
                         goto pick_me;
                 }
 
                 bmd.lock.arg = cpu_to_be32(0x3f);
-                bmd.lock.data = cpu_to_be32(card->local_node->node_id);
+                bmd.lock.data = cpu_to_be32(local_node->node_id);
 
                 spin_unlock_irqrestore(&card->lock, flags);
 
@@ -267,12 +279,12 @@ fw_card_bm_work(struct work_struct *work)
                          * Another bus reset happened. Just return,
                          * the BM work has been rescheduled.
                          */
-                        return;
+                        goto out;
                 }
 
                 if (bmd.rcode == RCODE_COMPLETE && bmd.old != 0x3f)
                         /* Somebody else is BM, let them do the work. */
-                        return;
+                        goto out;
 
                 spin_lock_irqsave(&card->lock, flags);
                 if (bmd.rcode != RCODE_COMPLETE) {
@@ -282,7 +294,7 @@ fw_card_bm_work(struct work_struct *work)
                          * do a bus reset and pick the local node as
                          * root, and thus, IRM.
                          */
-                        new_root_id = card->local_node->node_id;
+                        new_root_id = local_node->node_id;
                         fw_notify("BM lock failed, making local node (%02x) root.\n",
                                   new_root_id);
                         goto pick_me;
@@ -295,7 +307,7 @@ fw_card_bm_work(struct work_struct *work)
                  */
                 spin_unlock_irqrestore(&card->lock, flags);
                 schedule_delayed_work(&card->work, DIV_ROUND_UP(HZ, 10));
-                return;
+                goto out;
         }
 
         /*
@@ -305,20 +317,20 @@ fw_card_bm_work(struct work_struct *work)
          */
         card->bm_generation = generation;
 
-        if (root == NULL) {
+        if (root_device == NULL) {
                 /*
                  * Either link_on is false, or we failed to read the
                  * config rom.  In either case, pick another root.
                  */
-                new_root_id = card->local_node->node_id;
-        } else if (atomic_read(&root->state) != FW_DEVICE_RUNNING) {
+                new_root_id = local_node->node_id;
+        } else if (atomic_read(&root_device->state) != FW_DEVICE_RUNNING) {
                 /*
                  * If we haven't probed this device yet, bail out now
                  * and let's try again once that's done.
                  */
                 spin_unlock_irqrestore(&card->lock, flags);
-                return;
-        } else if (root->config_rom[2] & BIB_CMC) {
+                goto out;
+        } else if (root_device->config_rom[2] & BIB_CMC) {
                 /*
                  * FIXME: I suppose we should set the cmstr bit in the
                  * STATE_CLEAR register of this node, as described in
@@ -332,7 +344,7 @@ fw_card_bm_work(struct work_struct *work)
                  * successfully read the config rom, but it's not
                  * cycle master capable.
                  */
-                new_root_id = card->local_node->node_id;
+                new_root_id = local_node->node_id;
         }
 
  pick_me:
@@ -341,8 +353,8 @@ fw_card_bm_work(struct work_struct *work)
          * the typically much larger 1394b beta repeater delays though.
          */
         if (!card->beta_repeaters_present &&
-            card->root_node->max_hops < ARRAY_SIZE(gap_count_table))
-                gap_count = gap_count_table[card->root_node->max_hops];
+            root_node->max_hops < ARRAY_SIZE(gap_count_table))
+                gap_count = gap_count_table[root_node->max_hops];
         else
                 gap_count = 63;
 
@@ -364,6 +376,11 @@ fw_card_bm_work(struct work_struct *work)
                 fw_send_phy_config(card, new_root_id, generation, gap_count);
                 fw_core_initiate_bus_reset(card, 1);
         }
+ out:
+        if (root_device)
+                fw_device_put(root_device);
+        fw_node_put(root_node);
+        fw_node_put(local_node);
 }
 
 static void
diff --git a/drivers/firewire/fw-topology.c b/drivers/firewire/fw-topology.c
index 172c1867e9a..e47bb040197 100644
--- a/drivers/firewire/fw-topology.c
+++ b/drivers/firewire/fw-topology.c
@@ -383,6 +383,7 @@ void fw_destroy_nodes(struct fw_card *card)
         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);
 }