Commit cac9e441 authored by Jens Axboe's avatar Jens Axboe
Browse files

io_uring/net: save msghdr->msg_control for retries 

If the application sets ->msg_control and we have to later retry this
command, or if it got queued with IOSQE_ASYNC to begin with, then we
need to retain the original msg_control value. This is due to the net
stack overwriting this field with an in-kernel pointer, to copy it
in. Hitting that path for the second time will now fail the copy from
user, as it's attempting to copy from a non-user address.

Cc: stable@vger.kernel.org # 5.10+
Link: https://github.com/axboe/liburing/issues/880


Reported-and-tested-by: default avatarMarek Majkowski <marek@cloudflare.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent b6dad517

io_uring/net.c

+7 −1
Original line number Diff line number Diff line
@@ -65,6 +65,7 @@ struct io_sr_msg { 
	u16				addr_len;

	u16				buf_group;

	void __user			*addr;

	void __user			*msg_control;

	/* used only for send zerocopy */

	struct io_kiocb 		*notif;

};
@@ -195,11 +196,15 @@ static int io_sendmsg_copy_hdr(struct io_kiocb *req, 
			       struct io_async_msghdr *iomsg)

{

	struct io_sr_msg *sr = io_kiocb_to_cmd(req, struct io_sr_msg);

	int ret;



	iomsg->msg.msg_name = &iomsg->addr;

	iomsg->free_iov = iomsg->fast_iov;

	return sendmsg_copy_msghdr(&iomsg->msg, sr->umsg, sr->msg_flags,

	ret = sendmsg_copy_msghdr(&iomsg->msg, sr->umsg, sr->msg_flags,

					&iomsg->free_iov);

	/* save msg_control as sys_sendmsg() overwrites it */

	sr->msg_control = iomsg->msg.msg_control;

	return ret;

}



int io_send_prep_async(struct io_kiocb *req)
@@ -297,6 +302,7 @@ int io_sendmsg(struct io_kiocb *req, unsigned int issue_flags) 


	if (req_has_async_data(req)) {

		kmsg = req->async_data;

		kmsg->msg.msg_control = sr->msg_control;

	} else {

		ret = io_sendmsg_copy_hdr(req, &iomsg);

		if (ret)