firewire: Don't set card->irm_node before we have a new valid topology.

In case the topology build fails, we want to retain the old topology
info until another reset finishes and results in a valid new tree.  If
we clear card->irm_node to NULL and the topology build fails, we end up
dereferencing a NULL pointer in a few places.

Signed-off-by: Kristian Høgsberg <krh@redhat.com>
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>

1 files changed, 4 insertions, 3 deletions

diff --git a/drivers/firewire/fw-topology.c b/drivers/firewire/fw-topology.c
index 7923463fdbf3..bc8a3487c83a 100644
--- a/drivers/firewire/fw-topology.c
+++ b/drivers/firewire/fw-topology.c
@@ -166,7 +166,7 @@ static void update_hop_count(struct fw_node *node)
 static struct fw_node *build_tree(struct fw_card *card,
                                   u32 *sid, int self_id_count)
 {
-        struct fw_node *node, *child, *local_node;
+        struct fw_node *node, *child, *local_node, *irm_node;
         struct list_head stack, *h;
         u32 *next_sid, *end, q;
         int i, port_count, child_port_count, phy_id, parent_count, stack_depth;
@@ -178,7 +178,7 @@ static struct fw_node *build_tree(struct fw_card *card,
         stack_depth = 0;
         end = sid + self_id_count;
         phy_id = 0;
-        card->irm_node = NULL;
+        irm_node = NULL;
         gap_count = self_id_gap_count(*sid);
         topology_type = 0;
 
@@ -218,7 +218,7 @@ static struct fw_node *build_tree(struct fw_card *card,
                         local_node = node;
 
                 if (self_id_contender(q))
-                        card->irm_node = node;
+                        irm_node = node;
 
                 if (node->phy_speed == SCODE_BETA)
                         topology_type |= FW_TOPOLOGY_B;
@@ -282,6 +282,7 @@ static struct fw_node *build_tree(struct fw_card *card,
         }
 
         card->root_node = node;
+        card->irm_node = irm_node;
         card->gap_count = gap_count;
         card->topology_type = topology_type;