firewire: fill_bus_reset_event needs lock protection

Callers of fill_bus_reset_event() have to take card->lock.  Otherwise
access to node data may oops if node removal is in progress.

A lockless alternative would be

-	event->local_node_id = card->local_node->node_id;
+	tmp = fw_node_get(card->local_node);
+	event->local_node_id = tmp->node_id;
+	fw_node_put(tmp);

and ditto with the other node pointers which fill_bus_reset_event()
accesses.  But I went the locked route because one of the two callers
already holds the lock.  As a bonus, we don't need the memory barrier
anymore because device->generation and device->node_id are written in
a card->lock protected section.

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

1 files changed, 7 insertions, 2 deletions

diff --git a/drivers/firewire/fw-cdev.c b/drivers/firewire/fw-cdev.c
index dda14015e873..c639915fc3cb 100644
--- a/drivers/firewire/fw-cdev.c
+++ b/drivers/firewire/fw-cdev.c
@@ -205,6 +205,7 @@ fw_device_op_read(struct file *file,
         return dequeue_event(client, buffer, count);
 }
 
+/* caller must hold card->lock so that node pointers can be dereferenced here */
 static void
 fill_bus_reset_event(struct fw_cdev_event_bus_reset *event,
                      struct client *client)
@@ -214,7 +215,6 @@ fill_bus_reset_event(struct fw_cdev_event_bus_reset *event,
         event->closure       = client->bus_reset_closure;
         event->type          = FW_CDEV_EVENT_BUS_RESET;
         event->generation    = client->device->generation;
-        smp_rmb();           /* node_id must not be older than generation */
         event->node_id       = client->device->node_id;
         event->local_node_id = card->local_node->node_id;
         event->bm_node_id    = 0; /* FIXME: We don't track the BM. */
@@ -274,6 +274,7 @@ static int ioctl_get_info(struct client *client, void *buffer)
 {
         struct fw_cdev_get_info *get_info = buffer;
         struct fw_cdev_event_bus_reset bus_reset;
+        struct fw_card *card = client->device->card;
         unsigned long ret = 0;
 
         client->version = get_info->version;
@@ -299,13 +300,17 @@ static int ioctl_get_info(struct client *client, void *buffer)
         client->bus_reset_closure = get_info->bus_reset_closure;
         if (get_info->bus_reset != 0) {
                 void __user *uptr = u64_to_uptr(get_info->bus_reset);
+                unsigned long flags;
 
+                spin_lock_irqsave(&card->lock, flags);
                 fill_bus_reset_event(&bus_reset, client);
+                spin_unlock_irqrestore(&card->lock, flags);
+
                 if (copy_to_user(uptr, &bus_reset, sizeof(bus_reset)))
                         return -EFAULT;
         }
 
-        get_info->card = client->device->card->index;
+        get_info->card = card->index;
 
         return 0;
 }