net/macvtap: fix reference counting
The RCU usage in the original code was broken because
there are cases where we possibly sleep with rcu_read_lock
held. As a fix, change the macvtap_file_get_queue to
get a reference on the socket and the netdev instead of
taking the full rcu_read_lock.
Also, change macvtap_file_get_queue failure case to
not require a subsequent macvtap_file_put_queue, as
pointed out by Ed Swierk.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Ed Swierk <eswierk@aristanetworks.com>
Cc: Sridhar Samudrala <sri@us.ibm.com>
Acked-by: Sridhar Samudrala <sri@us.ibm.com>
Acked-by: Ed Swierk <eswierk@aristanetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
index ad1f6ef..fe7656b 100644
--- a/drivers/net/macvtap.c
+++ b/drivers/net/macvtap.c
@@ -70,7 +70,8 @@
* exists.
*
* The callbacks from macvlan are always done with rcu_read_lock held
- * already, while in the file_operations, we get it ourselves.
+ * already. For calls from file_operations, we use the rcu_read_lock_bh
+ * to get a reference count on the socket and the device.
*
* When destroying a queue, we remove the pointers from the file and
* from the dev and then synchronize_rcu to make sure no thread is
@@ -159,13 +160,21 @@
static inline struct macvtap_queue *macvtap_file_get_queue(struct file *file)
{
+ struct macvtap_queue *q;
rcu_read_lock_bh();
- return rcu_dereference(file->private_data);
+ q = rcu_dereference(file->private_data);
+ if (q) {
+ sock_hold(&q->sk);
+ dev_hold(q->vlan->dev);
+ }
+ rcu_read_unlock_bh();
+ return q;
}
-static inline void macvtap_file_put_queue(void)
+static inline void macvtap_file_put_queue(struct macvtap_queue *q)
{
- rcu_read_unlock_bh();
+ sock_put(&q->sk);
+ dev_put(q->vlan->dev);
}
/*
@@ -314,8 +323,8 @@
sock_writeable(&q->sk)))
mask |= POLLOUT | POLLWRNORM;
+ macvtap_file_put_queue(q);
out:
- macvtap_file_put_queue();
return mask;
}
@@ -366,8 +375,8 @@
result = macvtap_get_user(q, iv, iov_length(iv, count),
file->f_flags & O_NONBLOCK);
+ macvtap_file_put_queue(q);
out:
- macvtap_file_put_queue();
return result;
}
@@ -398,10 +407,8 @@
struct sk_buff *skb;
ssize_t len, ret = 0;
- if (!q) {
- ret = -ENOLINK;
- goto out;
- }
+ if (!q)
+ return -ENOLINK;
len = iov_length(iv, count);
if (len < 0) {
@@ -437,7 +444,7 @@
remove_wait_queue(q->sk.sk_sleep, &wait);
out:
- macvtap_file_put_queue();
+ macvtap_file_put_queue(q);
return ret;
}
@@ -468,7 +475,7 @@
if (!q)
return -ENOLINK;
memcpy(devname, q->vlan->dev->name, sizeof(devname));
- macvtap_file_put_queue();
+ macvtap_file_put_queue(q);
if (copy_to_user(&ifr->ifr_name, q->vlan->dev->name, IFNAMSIZ) ||
put_user((TUN_TAP_DEV | TUN_NO_PI), &ifr->ifr_flags))
@@ -485,8 +492,10 @@
return -EFAULT;
q = macvtap_file_get_queue(file);
+ if (!q)
+ return -ENOLINK;
q->sk.sk_sndbuf = u;
- macvtap_file_put_queue();
+ macvtap_file_put_queue(q);
return 0;
case TUNSETOFFLOAD: