net: add __sys_socket_file()

This works like __sys_socket(), except instead of allocating and
returning a socket fd, it just returns the file associated with the
socket. No fd is installed into the process file table.

This is similar to do_accept(), and allows io_uring to use this without
instantiating a file descriptor in the process file table.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
Acked-by: David S. Miller <davem@davemloft.net>
Link: https://lore.kernel.org/r/20220412202240.234207-2-axboe@kernel.dk

diff --git a/include/linux/socket.h b/include/linux/socket.h
index 6f85f5d..a1882e1 100644 (file)
--- a/include/linux/socket.h
+++ b/include/linux/socket.h
@@ -434,6 +434,7 @@ extern struct file *do_accept(struct file *file, unsigned file_flags,
 extern int __sys_accept4(int fd, struct sockaddr __user *upeer_sockaddr,
                         int __user *upeer_addrlen, int flags);
 extern int __sys_socket(int family, int type, int protocol);
+extern struct file *__sys_socket_file(int family, int type, int protocol);
 extern int __sys_bind(int fd, struct sockaddr __user *umyaddr, int addrlen);
 extern int __sys_connect_file(struct file *file, struct sockaddr_storage *addr,
                              int addrlen, int file_flags);

diff --git a/net/socket.c b/net/socket.c
index 6887840..bb6a1a1 100644 (file)
--- a/net/socket.c
+++ b/net/socket.c
@@ -504,7 +504,7 @@ static int sock_map_fd(struct socket *sock, int flags)
 struct socket *sock_from_file(struct file *file)
 {
        if (file->f_op == &socket_file_ops)
-               return file->private_data;      /* set in sock_map_fd */
+               return file->private_data;      /* set in sock_alloc_file */
 
        return NULL;
 }
@@ -1538,11 +1538,10 @@ int sock_create_kern(struct net *net, int family, int type, int protocol, struct
 }
 EXPORT_SYMBOL(sock_create_kern);
 
-int __sys_socket(int family, int type, int protocol)
+static struct socket *__sys_socket_create(int family, int type, int protocol)
 {
-       int retval;
        struct socket *sock;
-       int flags;
+       int retval;
 
        /* Check the SOCK_* constants for consistency.  */
        BUILD_BUG_ON(SOCK_CLOEXEC != O_CLOEXEC);
@@ -1550,17 +1549,50 @@ int __sys_socket(int family, int type, int protocol)
        BUILD_BUG_ON(SOCK_CLOEXEC & SOCK_TYPE_MASK);
        BUILD_BUG_ON(SOCK_NONBLOCK & SOCK_TYPE_MASK);
 
-       flags = type & ~SOCK_TYPE_MASK;
-       if (flags & ~(SOCK_CLOEXEC | SOCK_NONBLOCK))
-               return -EINVAL;
+       if ((type & ~SOCK_TYPE_MASK) & ~(SOCK_CLOEXEC | SOCK_NONBLOCK))
+               return ERR_PTR(-EINVAL);
        type &= SOCK_TYPE_MASK;
 
+       retval = sock_create(family, type, protocol, &sock);
+       if (retval < 0)
+               return ERR_PTR(retval);
+
+       return sock;
+}
+
+struct file *__sys_socket_file(int family, int type, int protocol)
+{
+       struct socket *sock;
+       struct file *file;
+       int flags;
+
+       sock = __sys_socket_create(family, type, protocol);
+       if (IS_ERR(sock))
+               return ERR_CAST(sock);
+
+       flags = type & ~SOCK_TYPE_MASK;
        if (SOCK_NONBLOCK != O_NONBLOCK && (flags & SOCK_NONBLOCK))
                flags = (flags & ~SOCK_NONBLOCK) | O_NONBLOCK;
 
-       retval = sock_create(family, type, protocol, &sock);
-       if (retval < 0)
-               return retval;
+       file = sock_alloc_file(sock, flags, NULL);
+       if (IS_ERR(file))
+               sock_release(sock);
+
+       return file;
+}
+
+int __sys_socket(int family, int type, int protocol)
+{
+       struct socket *sock;
+       int flags;
+
+       sock = __sys_socket_create(family, type, protocol);
+       if (IS_ERR(sock))
+               return PTR_ERR(sock);
+
+       flags = type & ~SOCK_TYPE_MASK;
+       if (SOCK_NONBLOCK != O_NONBLOCK && (flags & SOCK_NONBLOCK))
+               flags = (flags & ~SOCK_NONBLOCK) | O_NONBLOCK;
 
        return sock_map_fd(sock, flags & (O_CLOEXEC | O_NONBLOCK));
 }