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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>
This commit is contained in:
Arnd Bergmann 2010-02-11 05:55:39 +00:00 committed by David S. Miller
parent e9449d85c6
commit 564517e804
1 changed files with 22 additions and 13 deletions
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35
drivers/net/macvtap.c
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@ -70,7 +70,8 @@ static struct cdev macvtap_cdev;
* 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 void macvtap_del_queues(struct net_device *dev)
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 @@ static unsigned int macvtap_poll(struct file *file, poll_table * wait)
sock_writeable(&q->sk)))
mask |= POLLOUT | POLLWRNORM;
macvtap_file_put_queue(q);
out:
macvtap_file_put_queue();
return mask;
}
@ -366,8 +375,8 @@ static ssize_t macvtap_aio_write(struct kiocb *iocb, const struct iovec *iv,
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 @@ static ssize_t macvtap_aio_read(struct kiocb *iocb, const struct iovec *iv,
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 @@ static ssize_t macvtap_aio_read(struct kiocb *iocb, const struct iovec *iv,
remove_wait_queue(q->sk.sk_sleep, &wait);
out:
macvtap_file_put_queue();
macvtap_file_put_queue(q);
return ret;
}
@ -468,7 +475,7 @@ static long macvtap_ioctl(struct file *file, unsigned int cmd,
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 @@ static long macvtap_ioctl(struct file *file, unsigned int cmd,
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: