[PATCH 1/2] io_uring: call req_set_fail_links() on short send[msg]()/recv[msg]() calls

[Stefan Metzmacher <metze@samba.org>]

Without that it's not safe to use them in a linked combination with
others.

Now combinations like IORING_OP_SENDMSG followed by IORING_OP_SPLICE
should be possible.

We already handle short reads and writes for the following opcodes:

- IORING_OP_READV
- IORING_OP_READ_FIXED
- IORING_OP_READ
- IORING_OP_WRITEV
- IORING_OP_WRITE_FIXED
- IORING_OP_WRITE
- IORING_OP_SPLICE
- IORING_OP_TEE

Now we have it for these as well:

- IORING_OP_SENDMSG
- IORING_OP_SEND
- IORING_OP_RECVMSG
- IORING_OP_RECV

For IORING_OP_RECVMSG we also check for the MSG_TRUNC and MSG_CTRUNC
flags in order to call req_set_fail_links().

cc: stable@vger.kernel.org
Signed-off-by: Stefan Metzmacher <metze@samba.org>
---
 fs/io_uring.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index e88d9f95d0aa..f8a6a629e4db 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -4354,6 +4354,7 @@ static int io_sendmsg(struct io_kiocb *req, unsigned int issue_flags)
 	struct io_async_msghdr iomsg, *kmsg;
 	struct socket *sock;
 	unsigned flags;
+	int expected_ret;
 	int ret;
 
 	sock = sock_from_file(req->file);
@@ -4374,6 +4375,9 @@ static int io_sendmsg(struct io_kiocb *req, unsigned int issue_flags)
 	else if (issue_flags & IO_URING_F_NONBLOCK)
 		flags |= MSG_DONTWAIT;
 
+	expected_ret = iov_iter_count(&kmsg->msg.msg_iter);
+	if (unlikely(expected_ret == MAX_RW_COUNT))
+		expected_ret += 1;
 	ret = __sys_sendmsg_sock(sock, &kmsg->msg, flags);
 	if ((issue_flags & IO_URING_F_NONBLOCK) && ret == -EAGAIN)
 		return io_setup_async_msg(req, kmsg);
@@ -4384,7 +4388,7 @@ static int io_sendmsg(struct io_kiocb *req, unsigned int issue_flags)
 	if (kmsg->free_iov)
 		kfree(kmsg->free_iov);
 	req->flags &= ~REQ_F_NEED_CLEANUP;
-	if (ret < 0)
+	if (ret != expected_ret)
 		req_set_fail_links(req);
 	__io_req_complete(req, issue_flags, ret, 0);
 	return 0;
@@ -4425,7 +4429,7 @@ static int io_send(struct io_kiocb *req, unsigned int issue_flags)
 	if (ret == -ERESTARTSYS)
 		ret = -EINTR;
 
-	if (ret < 0)
+	if (ret != sr->len)
 		req_set_fail_links(req);
 	__io_req_complete(req, issue_flags, ret, 0);
 	return 0;
@@ -4577,6 +4581,7 @@ static int io_recvmsg(struct io_kiocb *req, unsigned int issue_flags)
 	struct socket *sock;
 	struct io_buffer *kbuf;
 	unsigned flags;
+	int expected_ret;
 	int ret, cflags = 0;
 	bool force_nonblock = issue_flags & IO_URING_F_NONBLOCK;
 
@@ -4608,6 +4613,9 @@ static int io_recvmsg(struct io_kiocb *req, unsigned int issue_flags)
 	else if (force_nonblock)
 		flags |= MSG_DONTWAIT;
 
+	expected_ret = iov_iter_count(&kmsg->msg.msg_iter);
+	if (unlikely(expected_ret == MAX_RW_COUNT))
+		expected_ret += 1;
 	ret = __sys_recvmsg_sock(sock, &kmsg->msg, req->sr_msg.umsg,
 					kmsg->uaddr, flags);
 	if (force_nonblock && ret == -EAGAIN)
@@ -4621,7 +4629,7 @@ static int io_recvmsg(struct io_kiocb *req, unsigned int issue_flags)
 	if (kmsg->free_iov)
 		kfree(kmsg->free_iov);
 	req->flags &= ~REQ_F_NEED_CLEANUP;
-	if (ret < 0)
+	if (ret != expected_ret || (kmsg->msg.msg_flags & (MSG_TRUNC | MSG_CTRUNC)))
 		req_set_fail_links(req);
 	__io_req_complete(req, issue_flags, ret, cflags);
 	return 0;
@@ -4675,7 +4683,7 @@ static int io_recv(struct io_kiocb *req, unsigned int issue_flags)
 out_free:
 	if (req->flags & REQ_F_BUFFER_SELECTED)
 		cflags = io_put_recv_kbuf(req);
-	if (ret < 0)
+	if (ret != sr->len)
 		req_set_fail_links(req);
 	__io_req_complete(req, issue_flags, ret, cflags);
 	return 0;
-- 
2.25.1