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firewire: fill_bus_reset_event needs lock protection

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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>
This commit is contained in:
Stefan Richter 2008-06-06 22:11:30 +02:00
parent affc9c24ad
commit 5cb84067d6
1 changed files with 7 additions and 2 deletions
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9
drivers/firewire/fw-cdev.c
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@ -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;
}