[PATCH 5/6] net: allow specific fd selection for __sys_accept4_file()

[Jens Axboe <axboe@xxxxxxxxx>]

If 'open_fd' being passed in is != -1, make accept4() use the specific
fd instead of finding a free unused one.

Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
---
 include/linux/socket.h | 2 +-
 net/socket.c           | 8 +++++---
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/include/linux/socket.h b/include/linux/socket.h
index fc59ac825561..ce6c97d4a439 100644
--- a/include/linux/socket.h
+++ b/include/linux/socket.h
@@ -405,7 +405,7 @@ extern int __sys_sendto(int fd, void __user *buff, size_t len,
 			int addr_len);
 extern int __sys_accept4_file(struct file *file, unsigned file_flags,
 			struct sockaddr __user *upeer_sockaddr,
-			 int __user *upeer_addrlen, int flags);
+			 int __user *upeer_addrlen, int flags, int open_fd);
 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);
diff --git a/net/socket.c b/net/socket.c
index 70ede74ab24b..a9793b778701 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -1707,7 +1707,7 @@ SYSCALL_DEFINE2(listen, int, fd, int, backlog)
 
 int __sys_accept4_file(struct file *file, unsigned file_flags,
 		       struct sockaddr __user *upeer_sockaddr,
-		       int __user *upeer_addrlen, int flags)
+		       int __user *upeer_addrlen, int flags, int open_fd)
 {
 	struct socket *sock, *newsock;
 	struct file *newfile;
@@ -1719,6 +1719,8 @@ int __sys_accept4_file(struct file *file, unsigned file_flags,
 
 	if (SOCK_NONBLOCK != O_NONBLOCK && (flags & SOCK_NONBLOCK))
 		flags = (flags & ~SOCK_NONBLOCK) | O_NONBLOCK;
+	if (open_fd != -1)
+		flags |= O_SPECIFIC_FD;
 
 	sock = sock_from_file(file, &err);
 	if (!sock)
@@ -1738,7 +1740,7 @@ int __sys_accept4_file(struct file *file, unsigned file_flags,
 	 */
 	__module_get(newsock->ops->owner);
 
-	newfd = get_unused_fd_flags(flags);
+	newfd = get_specific_unused_fd_flags(open_fd, flags);
 	if (unlikely(newfd < 0)) {
 		err = newfd;
 		sock_release(newsock);
@@ -1807,7 +1809,7 @@ int __sys_accept4(int fd, struct sockaddr __user *upeer_sockaddr,
 	f = fdget(fd);
 	if (f.file) {
 		ret = __sys_accept4_file(f.file, 0, upeer_sockaddr,
-						upeer_addrlen, flags);
+						upeer_addrlen, flags, -1);
 		if (f.flags)
 			fput(f.file);
 	}
-- 
2.25.1