af_unix: Return struct unix_sock from unix_get_socket().

Currently, unix_get_socket() returns struct sock, but after calling
it, we always cast it to unix_sk().

Let's return struct unix_sock from unix_get_socket().
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Acked-by: Pavel Begunkov <asml.silence@gmail.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://lore.kernel.org/r/20240123170856.41348-4-kuniyu@amazon.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

include/net/af_unix.h

@@ -14,7 +14,7 @@ void unix_destruct_scm(struct sk_buff *skb);
 void io_uring_destruct_scm(struct sk_buff *skb);
 void unix_gc(void);
 void wait_for_unix_gc(void);
-struct sock *unix_get_socket(struct file *filp);
+struct unix_sock *unix_get_socket(struct file *filp);
 struct sock *unix_peer_get(struct sock *sk);
 
 #define UNIX_HASH_MOD	(256 - 1)

net/unix/garbage.c

@@ -105,22 +105,17 @@ static void scan_inflight(struct sock *x, void (*func)(struct unix_sock *),
 
 			while (nfd--) {
 				/* Get the socket the fd matches if it indeed does so */
-				struct sock *sk = unix_get_socket(*fp++);
+				struct unix_sock *u = unix_get_socket(*fp++);
 
-				if (sk) {
-					struct unix_sock *u = unix_sk(sk);
-
-					/* Ignore non-candidates, they could
-					 * have been added to the queues after
-					 * starting the garbage collection
+				/* Ignore non-candidates, they could have been added
+				 * to the queues after starting the garbage collection
 				 */
-					if (test_bit(UNIX_GC_CANDIDATE, &u->gc_flags)) {
+				if (u && test_bit(UNIX_GC_CANDIDATE, &u->gc_flags)) {
 					hit = true;
 
 					func(u);
 				}
 			}
-			}
 			if (hit && hitlist != NULL) {
 				__skb_unlink(skb, &x->sk_receive_queue);
 				__skb_queue_tail(hitlist, skb);

net/unix/scm.c

@@ -21,9 +21,8 @@ EXPORT_SYMBOL(gc_inflight_list);
 DEFINE_SPINLOCK(unix_gc_lock);
 EXPORT_SYMBOL(unix_gc_lock);
 
-struct sock *unix_get_socket(struct file *filp)
+struct unix_sock *unix_get_socket(struct file *filp)
 {
-	struct sock *u_sock = NULL;
 	struct inode *inode = file_inode(filp);
 
 	/* Socket ? */
@@ -34,10 +33,10 @@ struct sock *unix_get_socket(struct file *filp)
 
 		/* PF_UNIX ? */
 		if (s && ops && ops->family == PF_UNIX)
-			u_sock = s;
+			return unix_sk(s);
 	}
 
-	return u_sock;
+	return NULL;
 }
 EXPORT_SYMBOL(unix_get_socket);
 
@@ -46,13 +45,11 @@ EXPORT_SYMBOL(unix_get_socket);
  */
 void unix_inflight(struct user_struct *user, struct file *fp)
 {
-	struct sock *s = unix_get_socket(fp);
+	struct unix_sock *u = unix_get_socket(fp);
 
 	spin_lock(&unix_gc_lock);
 
-	if (s) {
-		struct unix_sock *u = unix_sk(s);
-
+	if (u) {
 		if (!u->inflight) {
 			BUG_ON(!list_empty(&u->link));
 			list_add_tail(&u->link, &gc_inflight_list);
@@ -69,13 +66,11 @@ void unix_inflight(struct user_struct *user, struct file *fp)
 
 void unix_notinflight(struct user_struct *user, struct file *fp)
 {
-	struct sock *s = unix_get_socket(fp);
+	struct unix_sock *u = unix_get_socket(fp);
 
 	spin_lock(&unix_gc_lock);
 
-	if (s) {
-		struct unix_sock *u = unix_sk(s);
-
+	if (u) {
 		BUG_ON(!u->inflight);
 		BUG_ON(list_empty(&u->link));