diff options
Diffstat (limited to 'net/mctp/device.c')
| -rw-r--r-- | net/mctp/device.c | 21 |
1 files changed, 18 insertions, 3 deletions
diff --git a/net/mctp/device.c b/net/mctp/device.c index 9e097e61f23a..b754c31162b1 100644 --- a/net/mctp/device.c +++ b/net/mctp/device.c @@ -25,12 +25,25 @@ struct mctp_dump_cb { size_t a_idx; }; -/* unlocked: caller must hold rcu_read_lock */ +/* unlocked: caller must hold rcu_read_lock. + * Returned mctp_dev has its refcount incremented, or NULL if unset. + */ struct mctp_dev *__mctp_dev_get(const struct net_device *dev) { - return rcu_dereference(dev->mctp_ptr); + struct mctp_dev *mdev = rcu_dereference(dev->mctp_ptr); + + /* RCU guarantees that any mdev is still live. + * Zero refcount implies a pending free, return NULL. + */ + if (mdev) + if (!refcount_inc_not_zero(&mdev->refs)) + return NULL; + return mdev; } +/* Returned mctp_dev does not have refcount incremented. The returned pointer + * remains live while rtnl_lock is held, as that prevents mctp_unregister() + */ struct mctp_dev *mctp_dev_get_rtnl(const struct net_device *dev) { return rtnl_dereference(dev->mctp_ptr); @@ -124,6 +137,7 @@ static int mctp_dump_addrinfo(struct sk_buff *skb, struct netlink_callback *cb) if (mdev) { rc = mctp_dump_dev_addrinfo(mdev, skb, cb); + mctp_dev_put(mdev); // Error indicates full buffer, this // callback will get retried. if (rc < 0) @@ -298,7 +312,7 @@ void mctp_dev_hold(struct mctp_dev *mdev) void mctp_dev_put(struct mctp_dev *mdev) { - if (refcount_dec_and_test(&mdev->refs)) { + if (mdev && refcount_dec_and_test(&mdev->refs)) { dev_put(mdev->dev); kfree_rcu(mdev, rcu); } @@ -370,6 +384,7 @@ static size_t mctp_get_link_af_size(const struct net_device *dev, if (!mdev) return 0; ret = nla_total_size(4); /* IFLA_MCTP_NET */ + mctp_dev_put(mdev); return ret; } |