Merge branch 'af_unix-data-races'

Kuniyuki Iwashima says:

====================
af_unix: Fix four data-races.

While running syzkaller, KCSAN reported 3 data-races with
systemd-coredump using AF_UNIX sockets.

This series fixes the three and another one inspiered by
one of the reports.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

Author: davem330

net/core/sock.c

@@ -2747,9 +2747,9 @@ static long sock_wait_for_wmem(struct sock *sk, long timeo)
 		prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
 		if (refcount_read(&sk->sk_wmem_alloc) < READ_ONCE(sk->sk_sndbuf))
 			break;
-		if (sk->sk_shutdown & SEND_SHUTDOWN)
+		if (READ_ONCE(sk->sk_shutdown) & SEND_SHUTDOWN)
 			break;
-		if (sk->sk_err)
+		if (READ_ONCE(sk->sk_err))
 			break;
 		timeo = schedule_timeout(timeo);
 	}
@@ -2777,7 +2777,7 @@ struct sk_buff *sock_alloc_send_pskb(struct sock *sk, unsigned long header_len,
 			goto failure;
 
 		err = -EPIPE;
-		if (sk->sk_shutdown & SEND_SHUTDOWN)
+		if (READ_ONCE(sk->sk_shutdown) & SEND_SHUTDOWN)
 			goto failure;
 
 		if (sk_wmem_alloc_get(sk) < READ_ONCE(sk->sk_sndbuf))

net/unix/af_unix.c

@@ -680,7 +680,7 @@ static void unix_release_sock(struct sock *sk, int embrion)
 	 *	  What the above comment does talk about? --ANK(980817)
 	 */
 
-	if (unix_tot_inflight)
+	if (READ_ONCE(unix_tot_inflight))
 		unix_gc();		/* Garbage collect fds */
 }
 

net/unix/scm.c

@@ -64,7 +64,7 @@ void unix_inflight(struct user_struct *user, struct file *fp)
 		/* Paired with READ_ONCE() in wait_for_unix_gc() */
 		WRITE_ONCE(unix_tot_inflight, unix_tot_inflight + 1);
 	}
-	user->unix_inflight++;
+	WRITE_ONCE(user->unix_inflight, user->unix_inflight + 1);
 	spin_unlock(&unix_gc_lock);
 }
 
@@ -85,7 +85,7 @@ void unix_notinflight(struct user_struct *user, struct file *fp)
 		/* Paired with READ_ONCE() in wait_for_unix_gc() */
 		WRITE_ONCE(unix_tot_inflight, unix_tot_inflight - 1);
 	}
-	user->unix_inflight--;
+	WRITE_ONCE(user->unix_inflight, user->unix_inflight - 1);
 	spin_unlock(&unix_gc_lock);
 }
 
@@ -99,7 +99,7 @@ static inline bool too_many_unix_fds(struct task_struct *p)
 {
 	struct user_struct *user = current_user();
 
-	if (unlikely(user->unix_inflight > task_rlimit(p, RLIMIT_NOFILE)))
+	if (unlikely(READ_ONCE(user->unix_inflight) > task_rlimit(p, RLIMIT_NOFILE)))
 		return !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN);
 	return false;
 }