@@ -98,7 +98,6 @@ struct unix_sock {
#define unix_state_unlock(s) spin_unlock(&unix_sk(s)->lock)
enum unix_socket_lock_class {
U_LOCK_NORMAL,
- U_LOCK_SECOND, /* for double locking, see unix_state_double_lock(). */
U_LOCK_DIAG, /* used while dumping icons, see sk_diag_dump_icons(). */
U_LOCK_GC_LISTENER, /* used for listening socket while determining gc
* candidates to close a small race window.
@@ -143,6 +143,41 @@ static int unix_state_lock_cmp_fn(const struct lockdep_map *_a,
a = container_of(_a, struct unix_sock, lock.dep_map);
b = container_of(_b, struct unix_sock, lock.dep_map);
+ if (a->sk.sk_state == TCP_LISTEN) {
+ /* unix_stream_connect(): Before the 2nd unix_state_lock(),
+ *
+ * 1. a is TCP_LISTEN.
+ * 2. b is not a.
+ * 3. concurrent connect(b -> a) must fail.
+ *
+ * Except for 2. & 3., the b's state can be any possible
+ * value due to concurrent connect() or listen().
+ *
+ * 2. is detected in debug_spin_lock_before(), and 3. cannot
+ * be expressed as lock_cmp_fn.
+ */
+ switch (b->sk.sk_state) {
+ case TCP_CLOSE:
+ case TCP_ESTABLISHED:
+ case TCP_LISTEN:
+ return -1;
+ default:
+ /* Invalid case. */
+ return 0;
+ }
+ }
+
+ /* Should never happen. Just to be symmetric. */
+ if (b->sk.sk_state == TCP_LISTEN) {
+ switch (b->sk.sk_state) {
+ case TCP_CLOSE:
+ case TCP_ESTABLISHED:
+ return 1;
+ default:
+ return 0;
+ }
+ }
+
/* unix_state_double_lock(): ascending address order. */
return cmp_ptr(a, b);
}
@@ -1585,7 +1620,7 @@ static int unix_stream_connect(struct socket *sock, struct sockaddr *uaddr,
goto out_unlock;
}
- unix_state_lock_nested(sk, U_LOCK_SECOND);
+ unix_state_lock(sk);
if (unlikely(sk->sk_state != TCP_CLOSE)) {
err = sk->sk_state == TCP_ESTABLISHED ? -EISCONN : -EINVAL;
While a SOCK_(STREAM|SEQPACKET) socket connect()s to another, we hold two locks of them by unix_state_lock() and unix_state_lock_nested() in unix_stream_connect(). Before unix_state_lock_nested(), the following is guaranteed by checking sk->sk_state: 1. The first socket is TCP_LISTEN 2. The second socket is not the first one 3. Simultaneous connect() must fail So, the client state can be TCP_CLOSE or TCP_LISTEN or TCP_ESTABLISHED. Let's define the expected states as unix_state_lock_cmp_fn() instead of using unix_state_lock_nested(). Note that 2. is detected by debug_spin_lock_before() and 3. cannot be expressed as lock_cmp_fn. Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com> --- include/net/af_unix.h | 1 - net/unix/af_unix.c | 37 ++++++++++++++++++++++++++++++++++++- 2 files changed, 36 insertions(+), 2 deletions(-)