Subject: [PATCH 2/2] io_uring: make sure accept honor rlimit nofile

From: Jens Axboe <[email-masked]>
Date: Thu, 19 Mar 2020 20:22:16 -0600

Just like commit 21ec2da35ce3, this fixes the fact that
IORING_OP_ACCEPT ends up using get_unused_fd_flags(), which checks
current->signal->rlim[] for limits.

Add an extra argument to __sys_accept4_file() that allows us to pass
in the proper nofile limit, and grab it at request prep time.

Signed-off-by: Jens Axboe <[email-masked]>
---
 fs/io_uring.c          | 5 ++++-
 include/linux/socket.h | 3 ++-
 net/socket.c           | 8 +++++---
 3 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index fe5ded7c74ef..3affd96a98ba 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -343,6 +343,7 @@ struct io_accept {
 	struct sockaddr __user		*addr;
 	int __user			*addr_len;
 	int				flags;
+	unsigned long			nofile;
 };
 
 struct io_sync {
@@ -3324,6 +3325,7 @@ static int io_accept_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 	accept->addr = u64_to_user_ptr(READ_ONCE(sqe->addr));
 	accept->addr_len = u64_to_user_ptr(READ_ONCE(sqe->addr2));
 	accept->flags = READ_ONCE(sqe->accept_flags);
+	accept->nofile = rlimit(RLIMIT_NOFILE);
 	return 0;
 #else
 	return -EOPNOTSUPP;
@@ -3340,7 +3342,8 @@ static int __io_accept(struct io_kiocb *req, struct io_kiocb **nxt,
 
 	file_flags = force_nonblock ? O_NONBLOCK : 0;
 	ret = __sys_accept4_file(req->file, file_flags, accept->addr,
-					accept->addr_len, accept->flags);
+					accept->addr_len, accept->flags,
+					accept->nofile);
 	if (ret == -EAGAIN && force_nonblock)
 		return -EAGAIN;
 	if (ret == -ERESTARTSYS)
diff --git a/include/linux/socket.h b/include/linux/socket.h
index 2d2313403101..15f3412d481e 100644
--- a/include/linux/socket.h
+++ b/include/linux/socket.h
@@ -401,7 +401,8 @@ 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,
+			 unsigned long nofile);
 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 b79a05de7c6e..2eecf1517f76 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -1707,7 +1707,8 @@ 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,
+		       unsigned long nofile)
 {
 	struct socket *sock, *newsock;
 	struct file *newfile;
@@ -1738,7 +1739,7 @@ int __sys_accept4_file(struct file *file, unsigned file_flags,
 	 */
 	__module_get(newsock->ops->owner);
 
-	newfd = get_unused_fd_flags(flags);
+	newfd = __get_unused_fd_flags(flags, nofile);
 	if (unlikely(newfd < 0)) {
 		err = newfd;
 		sock_release(newsock);
@@ -1807,7 +1808,8 @@ 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,
+						rlimit(RLIMIT_NOFILE));
 		if (f.flags)
 			fput(f.file);
 	}
-- 
2.25.2