Re: [PATCH net] ax25: Fix refcount leak issues of ax25_dev
From: Dan Carpenter <hidden>
Date: 2024-05-04 11:04:33
Also in:
linux-hams, lkml
On Wed, May 01, 2024 at 02:02:18PM +0800, Duoming Zhou wrote:
quoted hunk ↗ jump to hunk
@@ -58,7 +59,6 @@ void ax25_dev_device_up(struct net_device *dev) return; } - refcount_set(&ax25_dev->refcount, 1);
Let's keep this here, and just delete the ax25_dev_hold(). It makes the diff smaller and I like setting the refcount earlier anyway.
dev->ax25_ptr = ax25_dev;
Let's move this assignment under the spinlock where ax25_dev_hold() was.
quoted hunk ↗ jump to hunk
ax25_dev->dev = dev; netdev_hold(dev, &ax25_dev->dev_tracker, GFP_KERNEL);@@ -88,7 +88,7 @@ void ax25_dev_device_up(struct net_device *dev) ax25_dev->next = ax25_dev_list; ax25_dev_list = ax25_dev; spin_unlock_bh(&ax25_dev_lock); - ax25_dev_hold(ax25_dev); + refcount_set(&ax25_dev->refcount, 1); ax25_register_dev_sysctl(ax25_dev); }@@ -135,7 +135,6 @@ void ax25_dev_device_down(struct net_device *dev) unlock_put: spin_unlock_bh(&ax25_dev_lock); - ax25_dev_put(ax25_dev); dev->ax25_ptr = NULL; netdev_put(dev, &ax25_dev->dev_tracker); ax25_dev_put(ax25_dev);
So far as I can see, the ax25_dev should be on the list. Also, I think
the dev->ax25_ptr = NULL; assignment should be under the lock. So this
code should just look like:
list_for_each_entry(s, &ax25_dev_list, list) {
if (s->forward == dev)
s->forward = NULL;
}
list_for_each_entry(s, &ax25_dev_list, list) {
if (s == ax25_dev) {
list_del(&s->list);
break;
}
}
dev->ax25_ptr = NULL;
spin_unlock_bh(&ax25_dev_lock);
netdev_put(dev, &ax25_dev->dev_tracker);
ax25_dev_put(ax25_dev);
}
Also it should just be on the list once... In fact, it's impossible for
one pointer to be on a list twice. So it would be nice to add a break;
in ax25_addr_ax25dev(). It doesn't change the code, it just makes it
more obvious.
ax25_dev *ax25_addr_ax25dev(ax25_address *addr)
{
ax25_dev *ax25_dev, *res = NULL;
spin_lock_bh(&ax25_dev_lock);
list_for_each_entry(ax25_dev, &ax25_dev_list, list) {
if (ax25cmp(addr, (const ax25_address *)ax25_dev->dev->dev_addr) == 0) {
res = ax25_dev;
ax25_dev_hold(res);
break;
}
}
spin_unlock_bh(&ax25_dev_lock);
return res;
}
regards,
dan carpenter