linux-kernel - [PATCH 3/8] unix_bind(): separate BSD and abstract cases

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Message-Id: <20210222191222.4093800-3-viro@zeniv.linux.org.uk>
Date:   Mon, 22 Feb 2021 19:12:17 +0000
From:   Al Viro <viro@...iv.linux.org.uk>
To:     netdev@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        Christoph Hellwig <hch@...radead.org>,
        Jakub Kicinski <kuba@...nel.org>,
        Denis Kirjanov <kda@...ux-powerpc.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Cong Wang <xiyou.wangcong@...il.com>
Subject: [PATCH 3/8] unix_bind(): separate BSD and abstract cases

We do get some duplication that way, but it's minor compared to
parts that are different.  What we get is an ability to change
locking in BSD case without making failure exits very hard to
follow.

Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
---
 net/unix/af_unix.c | 55 +++++++++++++++++++++++++++++++++---------------------
 1 file changed, 34 insertions(+), 21 deletions(-)

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 54f1bfe14191..496b069c99fe 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -1022,7 +1022,6 @@ static int unix_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
 	int err;
 	unsigned int hash;
 	struct unix_address *addr;
-	struct path path = { };
 
 	err = -EINVAL;
 	if (addr_len < offsetofend(struct sockaddr_un, sun_family) ||
@@ -1049,6 +1048,7 @@ static int unix_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
 	refcount_set(&addr->refcnt, 1);
 
 	if (sun_path[0]) {
+		struct path path = { };
 		umode_t mode = S_IFSOCK |
 		       (SOCK_INODE(sock)->i_mode & ~current_umask());
 		err = unix_mknod(sun_path, mode, &path);
@@ -1057,41 +1057,54 @@ static int unix_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
 				err = -EADDRINUSE;
 			goto out_addr;
 		}
-	}
 
-	err = mutex_lock_interruptible(&u->bindlock);
-	if (err)
-		goto out_put;
+		err = mutex_lock_interruptible(&u->bindlock);
+		if (err) {
+			path_put(&path);
+			goto out_addr;
+		}
 
-	err = -EINVAL;
-	if (u->addr)
-		goto out_up;
+		err = -EINVAL;
+		if (u->addr) {
+			mutex_unlock(&u->bindlock);
+			path_put(&path);
+			goto out_addr;
+		}
 
-	if (sun_path[0]) {
 		addr->hash = UNIX_HASH_SIZE;
 		hash = d_backing_inode(path.dentry)->i_ino & (UNIX_HASH_SIZE - 1);
 		spin_lock(&unix_table_lock);
 		u->path = path;
+		__unix_set_addr(sk, addr, hash);
+		spin_unlock(&unix_table_lock);
+		mutex_unlock(&u->bindlock);
+		addr = NULL;
+		err = 0;
 	} else {
+		err = mutex_lock_interruptible(&u->bindlock);
+		if (err)
+			goto out_addr;
+
+		err = -EINVAL;
+		if (u->addr) {
+			mutex_unlock(&u->bindlock);
+			goto out_addr;
+		}
+
 		spin_lock(&unix_table_lock);
 		err = -EADDRINUSE;
 		if (__unix_find_socket_byname(net, sunaddr, addr_len,
 					      sk->sk_type, hash)) {
 			spin_unlock(&unix_table_lock);
-			goto out_up;
+			mutex_unlock(&u->bindlock);
+			goto out_addr;
 		}
-		hash = addr->hash;
+		__unix_set_addr(sk, addr, addr->hash);
+		spin_unlock(&unix_table_lock);
+		mutex_unlock(&u->bindlock);
+		addr = NULL;
+		err = 0;
 	}
-
-	__unix_set_addr(sk, addr, hash);
-	spin_unlock(&unix_table_lock);
-	addr = NULL;
-	err = 0;
-out_up:
-	mutex_unlock(&u->bindlock);
-out_put:
-	if (err)
-		path_put(&path);
 out_addr:
 	if (addr)
 		unix_release_addr(addr);
-- 
2.11.0