unix_bind_bsd(): move done_path_create() call after dealing with ->bindlock

Final preparations for doing unlink on failure past the successful
mknod.  We can't hold ->bindlock over ->mknod() or ->unlink(), since
either might do sb_start_write() (e.g. on overlayfs).  However, we
can do it while holding filesystem and VFS locks - doing
	kern_path_create()
	vfs_mknod()
	grab ->bindlock
	if u->addr had been set
		drop ->bindlock
		done_path_create
		return -EINVAL
	else
		assign the address to socket
		drop ->bindlock
		done_path_create
		return 0
would be deadlock-free.  Here we massage unix_bind_bsd() to that
form.  We are still doing equivalent transformations.

Next commit will *not* be an equivalent transformation - it will
add a call of vfs_unlink() before done_path_create() in "alread bound"
case.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index fe337dc..25dda9c 100644 (file)
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -989,8 +989,8 @@ static int unix_bind_bsd(struct sock *sk, struct unix_address *addr)
        struct unix_sock *u = unix_sk(sk);
        umode_t mode = S_IFSOCK |
               (SOCK_INODE(sk->sk_socket)->i_mode & ~current_umask());
-       struct path parent, path;
        struct user_namespace *ns; // barf...
+       struct path parent;
        struct dentry *dentry;
        unsigned int hash;
        int err;
@@ -1008,36 +1008,32 @@ static int unix_bind_bsd(struct sock *sk, struct unix_address *addr)
         * All right, let's create it.
         */
        err = security_path_mknod(&parent, dentry, mode, 0);
-       if (!err) {
+       if (!err)
                err = vfs_mknod(ns, d_inode(parent.dentry), dentry, mode, 0);
-               if (!err) {
-                       path.mnt = mntget(parent.mnt);
-                       path.dentry = dget(dentry);
-               }
-       }
-       done_path_create(&parent, dentry);
-       if (err)
+       if (err) {
+               done_path_create(&parent, dentry);
                return err;
-
+       }
        err = mutex_lock_interruptible(&u->bindlock);
        if (err) {
-               path_put(&path);
+               done_path_create(&parent, dentry);
                return err;
        }
-
        if (u->addr) {
                mutex_unlock(&u->bindlock);
-               path_put(&path);
+               done_path_create(&parent, dentry);
                return -EINVAL;
        }
 
        addr->hash = UNIX_HASH_SIZE;
-       hash = d_backing_inode(path.dentry)->i_ino & (UNIX_HASH_SIZE - 1);
+       hash = d_backing_inode(dentry)->i_ino & (UNIX_HASH_SIZE - 1);
        spin_lock(&unix_table_lock);
-       u->path = path;
+       u->path.mnt = mntget(parent.mnt);
+       u->path.dentry = dget(dentry);
        __unix_set_addr(sk, addr, hash);
        spin_unlock(&unix_table_lock);
        mutex_unlock(&u->bindlock);
+       done_path_create(&parent, dentry);
        return 0;
 }