1// SPDX-License-Identifier: GPL-2.0
2#include <linux/kernel.h>
3#include <linux/errno.h>
4#include <linux/file.h>
5#include <linux/slab.h>
6#include <linux/nospec.h>
7#include <linux/io_uring.h>
8
9#include <uapi/linux/io_uring.h>
10
11#include "io_uring.h"
12#include "rsrc.h"
13#include "filetable.h"
14#include "msg_ring.h"
15
16
17/* All valid masks for MSG_RING */
18#define IORING_MSG_RING_MASK		(IORING_MSG_RING_CQE_SKIP | \
19					IORING_MSG_RING_FLAGS_PASS)
20
21struct io_msg {
22	struct file			*file;
23	struct file			*src_file;
24	struct callback_head		tw;
25	u64 user_data;
26	u32 len;
27	u32 cmd;
28	u32 src_fd;
29	union {
30		u32 dst_fd;
31		u32 cqe_flags;
32	};
33	u32 flags;
34};
35
36static void io_double_unlock_ctx(struct io_ring_ctx *octx)
37{
38	mutex_unlock(&octx->uring_lock);
39}
40
41static int io_double_lock_ctx(struct io_ring_ctx *octx,
42			      unsigned int issue_flags)
43{
44	/*
45	 * To ensure proper ordering between the two ctxs, we can only
46	 * attempt a trylock on the target. If that fails and we already have
47	 * the source ctx lock, punt to io-wq.
48	 */
49	if (!(issue_flags & IO_URING_F_UNLOCKED)) {
50		if (!mutex_trylock(&octx->uring_lock))
51			return -EAGAIN;
52		return 0;
53	}
54	mutex_lock(&octx->uring_lock);
55	return 0;
56}
57
58void io_msg_ring_cleanup(struct io_kiocb *req)
59{
60	struct io_msg *msg = io_kiocb_to_cmd(req, struct io_msg);
61
62	if (WARN_ON_ONCE(!msg->src_file))
63		return;
64
65	fput(msg->src_file);
66	msg->src_file = NULL;
67}
68
69static inline bool io_msg_need_remote(struct io_ring_ctx *target_ctx)
70{
71	if (!target_ctx->task_complete)
72		return false;
73	return current != target_ctx->submitter_task;
74}
75
76static int io_msg_exec_remote(struct io_kiocb *req, task_work_func_t func)
77{
78	struct io_ring_ctx *ctx = req->file->private_data;
79	struct io_msg *msg = io_kiocb_to_cmd(req, struct io_msg);
80	struct task_struct *task = READ_ONCE(ctx->submitter_task);
81
82	if (unlikely(!task))
83		return -EOWNERDEAD;
84
85	init_task_work(&msg->tw, func);
86	if (task_work_add(task, &msg->tw, TWA_SIGNAL))
87		return -EOWNERDEAD;
88
89	return IOU_ISSUE_SKIP_COMPLETE;
90}
91
92static void io_msg_tw_complete(struct callback_head *head)
93{
94	struct io_msg *msg = container_of(head, struct io_msg, tw);
95	struct io_kiocb *req = cmd_to_io_kiocb(msg);
96	struct io_ring_ctx *target_ctx = req->file->private_data;
97	int ret = 0;
98
99	if (current->flags & PF_EXITING) {
100		ret = -EOWNERDEAD;
101	} else {
102		u32 flags = 0;
103
104		if (msg->flags & IORING_MSG_RING_FLAGS_PASS)
105			flags = msg->cqe_flags;
106
107		/*
108		 * If the target ring is using IOPOLL mode, then we need to be
109		 * holding the uring_lock for posting completions. Other ring
110		 * types rely on the regular completion locking, which is
111		 * handled while posting.
112		 */
113		if (target_ctx->flags & IORING_SETUP_IOPOLL)
114			mutex_lock(&target_ctx->uring_lock);
115		if (!io_post_aux_cqe(target_ctx, msg->user_data, msg->len, flags))
116			ret = -EOVERFLOW;
117		if (target_ctx->flags & IORING_SETUP_IOPOLL)
118			mutex_unlock(&target_ctx->uring_lock);
119	}
120
121	if (ret < 0)
122		req_set_fail(req);
123	io_req_queue_tw_complete(req, ret);
124}
125
126static int io_msg_ring_data(struct io_kiocb *req, unsigned int issue_flags)
127{
128	struct io_ring_ctx *target_ctx = req->file->private_data;
129	struct io_msg *msg = io_kiocb_to_cmd(req, struct io_msg);
130	u32 flags = 0;
131	int ret;
132
133	if (msg->src_fd || msg->flags & ~IORING_MSG_RING_FLAGS_PASS)
134		return -EINVAL;
135	if (!(msg->flags & IORING_MSG_RING_FLAGS_PASS) && msg->dst_fd)
136		return -EINVAL;
137	if (target_ctx->flags & IORING_SETUP_R_DISABLED)
138		return -EBADFD;
139
140	if (io_msg_need_remote(target_ctx))
141		return io_msg_exec_remote(req, io_msg_tw_complete);
142
143	if (msg->flags & IORING_MSG_RING_FLAGS_PASS)
144		flags = msg->cqe_flags;
145
146	ret = -EOVERFLOW;
147	if (target_ctx->flags & IORING_SETUP_IOPOLL) {
148		if (unlikely(io_double_lock_ctx(target_ctx, issue_flags)))
149			return -EAGAIN;
150	}
151	if (io_post_aux_cqe(target_ctx, msg->user_data, msg->len, flags))
152		ret = 0;
153	if (target_ctx->flags & IORING_SETUP_IOPOLL)
154		io_double_unlock_ctx(target_ctx);
155	return ret;
156}
157
158static struct file *io_msg_grab_file(struct io_kiocb *req, unsigned int issue_flags)
159{
160	struct io_msg *msg = io_kiocb_to_cmd(req, struct io_msg);
161	struct io_ring_ctx *ctx = req->ctx;
162	struct file *file = NULL;
163	int idx = msg->src_fd;
164
165	io_ring_submit_lock(ctx, issue_flags);
166	if (likely(idx < ctx->nr_user_files)) {
167		idx = array_index_nospec(idx, ctx->nr_user_files);
168		file = io_file_from_index(&ctx->file_table, idx);
169		if (file)
170			get_file(file);
171	}
172	io_ring_submit_unlock(ctx, issue_flags);
173	return file;
174}
175
176static int io_msg_install_complete(struct io_kiocb *req, unsigned int issue_flags)
177{
178	struct io_ring_ctx *target_ctx = req->file->private_data;
179	struct io_msg *msg = io_kiocb_to_cmd(req, struct io_msg);
180	struct file *src_file = msg->src_file;
181	int ret;
182
183	if (unlikely(io_double_lock_ctx(target_ctx, issue_flags)))
184		return -EAGAIN;
185
186	ret = __io_fixed_fd_install(target_ctx, src_file, msg->dst_fd);
187	if (ret < 0)
188		goto out_unlock;
189
190	msg->src_file = NULL;
191	req->flags &= ~REQ_F_NEED_CLEANUP;
192
193	if (msg->flags & IORING_MSG_RING_CQE_SKIP)
194		goto out_unlock;
195	/*
196	 * If this fails, the target still received the file descriptor but
197	 * wasn't notified of the fact. This means that if this request
198	 * completes with -EOVERFLOW, then the sender must ensure that a
199	 * later IORING_OP_MSG_RING delivers the message.
200	 */
201	if (!io_post_aux_cqe(target_ctx, msg->user_data, ret, 0))
202		ret = -EOVERFLOW;
203out_unlock:
204	io_double_unlock_ctx(target_ctx);
205	return ret;
206}
207
208static void io_msg_tw_fd_complete(struct callback_head *head)
209{
210	struct io_msg *msg = container_of(head, struct io_msg, tw);
211	struct io_kiocb *req = cmd_to_io_kiocb(msg);
212	int ret = -EOWNERDEAD;
213
214	if (!(current->flags & PF_EXITING))
215		ret = io_msg_install_complete(req, IO_URING_F_UNLOCKED);
216	if (ret < 0)
217		req_set_fail(req);
218	io_req_queue_tw_complete(req, ret);
219}
220
221static int io_msg_send_fd(struct io_kiocb *req, unsigned int issue_flags)
222{
223	struct io_ring_ctx *target_ctx = req->file->private_data;
224	struct io_msg *msg = io_kiocb_to_cmd(req, struct io_msg);
225	struct io_ring_ctx *ctx = req->ctx;
226	struct file *src_file = msg->src_file;
227
228	if (msg->len)
229		return -EINVAL;
230	if (target_ctx == ctx)
231		return -EINVAL;
232	if (target_ctx->flags & IORING_SETUP_R_DISABLED)
233		return -EBADFD;
234	if (!src_file) {
235		src_file = io_msg_grab_file(req, issue_flags);
236		if (!src_file)
237			return -EBADF;
238		msg->src_file = src_file;
239		req->flags |= REQ_F_NEED_CLEANUP;
240	}
241
242	if (io_msg_need_remote(target_ctx))
243		return io_msg_exec_remote(req, io_msg_tw_fd_complete);
244	return io_msg_install_complete(req, issue_flags);
245}
246
247int io_msg_ring_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
248{
249	struct io_msg *msg = io_kiocb_to_cmd(req, struct io_msg);
250
251	if (unlikely(sqe->buf_index || sqe->personality))
252		return -EINVAL;
253
254	msg->src_file = NULL;
255	msg->user_data = READ_ONCE(sqe->off);
256	msg->len = READ_ONCE(sqe->len);
257	msg->cmd = READ_ONCE(sqe->addr);
258	msg->src_fd = READ_ONCE(sqe->addr3);
259	msg->dst_fd = READ_ONCE(sqe->file_index);
260	msg->flags = READ_ONCE(sqe->msg_ring_flags);
261	if (msg->flags & ~IORING_MSG_RING_MASK)
262		return -EINVAL;
263
264	return 0;
265}
266
267int io_msg_ring(struct io_kiocb *req, unsigned int issue_flags)
268{
269	struct io_msg *msg = io_kiocb_to_cmd(req, struct io_msg);
270	int ret;
271
272	ret = -EBADFD;
273	if (!io_is_uring_fops(req->file))
274		goto done;
275
276	switch (msg->cmd) {
277	case IORING_MSG_DATA:
278		ret = io_msg_ring_data(req, issue_flags);
279		break;
280	case IORING_MSG_SEND_FD:
281		ret = io_msg_send_fd(req, issue_flags);
282		break;
283	default:
284		ret = -EINVAL;
285		break;
286	}
287
288done:
289	if (ret < 0) {
290		if (ret == -EAGAIN || ret == IOU_ISSUE_SKIP_COMPLETE)
291			return ret;
292		req_set_fail(req);
293	}
294	io_req_set_res(req, ret, 0);
295	return IOU_OK;
296}
297