af_unix: Define locking order for U_LOCK_SECOND in unix_state_double_lock().

unix_dgram_connect() and unix_dgram_{send,recv}msg() lock the socket
and peer in ascending order of the socket address.

Let's define the order as unix_state_lock_cmp_fn() instead of using
unix_state_lock_nested().

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: Kent Overstreet <kent.overstreet@linux.dev>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 7889d47239595fe2e4765741d0e61295a53f6c88..0657f599bbef7c479a1c508e50f122b46784fa0b 100644 (file)
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -134,6 +134,18 @@ static int unix_table_lock_cmp_fn(const struct lockdep_map *a,
 {
        return cmp_ptr(a, b);
 }
+
+static int unix_state_lock_cmp_fn(const struct lockdep_map *_a,
+                                 const struct lockdep_map *_b)
+{
+       const struct unix_sock *a, *b;
+
+       a = container_of(_a, struct unix_sock, lock.dep_map);
+       b = container_of(_b, struct unix_sock, lock.dep_map);
+
+       /* unix_state_double_lock(): ascending address order. */
+       return cmp_ptr(a, b);
+}
 #endif
 
 static unsigned int unix_unbound_hash(struct sock *sk)
@@ -987,6 +999,7 @@ static struct sock *unix_create1(struct net *net, struct socket *sock, int kern,
        u->path.dentry = NULL;
        u->path.mnt = NULL;
        spin_lock_init(&u->lock);
+       lock_set_cmp_fn(&u->lock, unix_state_lock_cmp_fn, NULL);
        mutex_init(&u->iolock); /* single task reading lock */
        mutex_init(&u->bindlock); /* single task binding lock */
        init_waitqueue_head(&u->peer_wait);
@@ -1335,11 +1348,12 @@ static void unix_state_double_lock(struct sock *sk1, struct sock *sk2)
                unix_state_lock(sk1);
                return;
        }
+
        if (sk1 > sk2)
                swap(sk1, sk2);
 
        unix_state_lock(sk1);
-       unix_state_lock_nested(sk2, U_LOCK_SECOND);
+       unix_state_lock(sk2);
 }
 
 static void unix_state_double_unlock(struct sock *sk1, struct sock *sk2)