Date: Fri, 6 Jun 2008 22:11:30 +0200 (CEST) From: Stefan Richter Subject: 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 Signed-off-by: Kristian Høgsberg --- drivers/firewire/fw-cdev.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) Index: linux/drivers/firewire/fw-cdev.c =================================================================== --- linux.orig/drivers/firewire/fw-cdev.c +++ linux/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_even 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 { 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->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; }