net: mctp: add an explicit reference from a mctp_sk_key to sock

Currently, we correlate the mctp_sk_key lifetime to the sock lifetime
through the sock hash/unhash operations, but this is pretty tenuous, and
there are cases where we may have a temporary reference to an unhashed
sk.

This change makes the reference more explicit, by adding a hold on the
sock when it's associated with a mctp_sk_key, released on final key
unref.

Fixes: 73c618456dc5 ("mctp: locking, lifetime and validity changes for sk_keys")
Signed-off-by: Jeremy Kerr <jk@codeconstruct.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/mctp/route.c b/net/mctp/route.c
index f9a80b8..ce10ba7 100644 (file)
--- a/net/mctp/route.c
+++ b/net/mctp/route.c
@@ -147,6 +147,7 @@ static struct mctp_sk_key *mctp_key_alloc(struct mctp_sock *msk,
        key->valid = true;
        spin_lock_init(&key->lock);
        refcount_set(&key->refs, 1);
+       sock_hold(key->sk);
 
        return key;
 }
@@ -165,6 +166,7 @@ void mctp_key_unref(struct mctp_sk_key *key)
        mctp_dev_release_key(key->dev, key);
        spin_unlock_irqrestore(&key->lock, flags);
 
+       sock_put(key->sk);
        kfree(key);
 }
 
@@ -419,14 +421,14 @@ static int mctp_route_input(struct mctp_route *route, struct sk_buff *skb)
                         * this function.
                         */
                        rc = mctp_key_add(key, msk);
-                       if (rc) {
-                               kfree(key);
-                       } else {
+                       if (!rc)
                                trace_mctp_key_acquire(key);
 
-                               /* we don't need to release key->lock on exit */
-                               mctp_key_unref(key);
-                       }
+                       /* we don't need to release key->lock on exit, so
+                        * clean up here and suppress the unlock via
+                        * setting to NULL
+                        */
+                       mctp_key_unref(key);
                        key = NULL;
 
                } else {