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 
21 struct 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 
io_double_unlock_ctx(struct io_ring_ctx * octx)36 static void io_double_unlock_ctx(struct io_ring_ctx *octx)
37 {
38 	mutex_unlock(&octx->uring_lock);
39 }
40 
io_double_lock_ctx(struct io_ring_ctx * octx,unsigned int issue_flags)41 static 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 
io_msg_ring_cleanup(struct io_kiocb * req)58 void 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 
io_msg_need_remote(struct io_ring_ctx * target_ctx)69 static 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 
io_msg_exec_remote(struct io_kiocb * req,task_work_func_t func)76 static 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(ctx->submitter_task, &msg->tw, TWA_SIGNAL))
87 		return -EOWNERDEAD;
88 
89 	return IOU_ISSUE_SKIP_COMPLETE;
90 }
91 
io_msg_tw_complete(struct callback_head * head)92 static 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 
io_msg_ring_data(struct io_kiocb * req,unsigned int issue_flags)126 static 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 		if (io_post_aux_cqe(target_ctx, msg->user_data, msg->len, flags))
151 			ret = 0;
152 		io_double_unlock_ctx(target_ctx);
153 	} else {
154 		if (io_post_aux_cqe(target_ctx, msg->user_data, msg->len, flags))
155 			ret = 0;
156 	}
157 	return ret;
158 }
159 
io_msg_grab_file(struct io_kiocb * req,unsigned int issue_flags)160 static struct file *io_msg_grab_file(struct io_kiocb *req, unsigned int issue_flags)
161 {
162 	struct io_msg *msg = io_kiocb_to_cmd(req, struct io_msg);
163 	struct io_ring_ctx *ctx = req->ctx;
164 	struct file *file = NULL;
165 	int idx = msg->src_fd;
166 
167 	io_ring_submit_lock(ctx, issue_flags);
168 	if (likely(idx < ctx->nr_user_files)) {
169 		idx = array_index_nospec(idx, ctx->nr_user_files);
170 		file = io_file_from_index(&ctx->file_table, idx);
171 		if (file)
172 			get_file(file);
173 	}
174 	io_ring_submit_unlock(ctx, issue_flags);
175 	return file;
176 }
177 
io_msg_install_complete(struct io_kiocb * req,unsigned int issue_flags)178 static int io_msg_install_complete(struct io_kiocb *req, unsigned int issue_flags)
179 {
180 	struct io_ring_ctx *target_ctx = req->file->private_data;
181 	struct io_msg *msg = io_kiocb_to_cmd(req, struct io_msg);
182 	struct file *src_file = msg->src_file;
183 	int ret;
184 
185 	if (unlikely(io_double_lock_ctx(target_ctx, issue_flags)))
186 		return -EAGAIN;
187 
188 	ret = __io_fixed_fd_install(target_ctx, src_file, msg->dst_fd);
189 	if (ret < 0)
190 		goto out_unlock;
191 
192 	msg->src_file = NULL;
193 	req->flags &= ~REQ_F_NEED_CLEANUP;
194 
195 	if (msg->flags & IORING_MSG_RING_CQE_SKIP)
196 		goto out_unlock;
197 	/*
198 	 * If this fails, the target still received the file descriptor but
199 	 * wasn't notified of the fact. This means that if this request
200 	 * completes with -EOVERFLOW, then the sender must ensure that a
201 	 * later IORING_OP_MSG_RING delivers the message.
202 	 */
203 	if (!io_post_aux_cqe(target_ctx, msg->user_data, ret, 0))
204 		ret = -EOVERFLOW;
205 out_unlock:
206 	io_double_unlock_ctx(target_ctx);
207 	return ret;
208 }
209 
io_msg_tw_fd_complete(struct callback_head * head)210 static void io_msg_tw_fd_complete(struct callback_head *head)
211 {
212 	struct io_msg *msg = container_of(head, struct io_msg, tw);
213 	struct io_kiocb *req = cmd_to_io_kiocb(msg);
214 	int ret = -EOWNERDEAD;
215 
216 	if (!(current->flags & PF_EXITING))
217 		ret = io_msg_install_complete(req, IO_URING_F_UNLOCKED);
218 	if (ret < 0)
219 		req_set_fail(req);
220 	io_req_queue_tw_complete(req, ret);
221 }
222 
io_msg_send_fd(struct io_kiocb * req,unsigned int issue_flags)223 static int io_msg_send_fd(struct io_kiocb *req, unsigned int issue_flags)
224 {
225 	struct io_ring_ctx *target_ctx = req->file->private_data;
226 	struct io_msg *msg = io_kiocb_to_cmd(req, struct io_msg);
227 	struct io_ring_ctx *ctx = req->ctx;
228 	struct file *src_file = msg->src_file;
229 
230 	if (msg->len)
231 		return -EINVAL;
232 	if (target_ctx == ctx)
233 		return -EINVAL;
234 	if (target_ctx->flags & IORING_SETUP_R_DISABLED)
235 		return -EBADFD;
236 	if (!src_file) {
237 		src_file = io_msg_grab_file(req, issue_flags);
238 		if (!src_file)
239 			return -EBADF;
240 		msg->src_file = src_file;
241 		req->flags |= REQ_F_NEED_CLEANUP;
242 	}
243 
244 	if (io_msg_need_remote(target_ctx))
245 		return io_msg_exec_remote(req, io_msg_tw_fd_complete);
246 	return io_msg_install_complete(req, issue_flags);
247 }
248 
io_msg_ring_prep(struct io_kiocb * req,const struct io_uring_sqe * sqe)249 int io_msg_ring_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
250 {
251 	struct io_msg *msg = io_kiocb_to_cmd(req, struct io_msg);
252 
253 	if (unlikely(sqe->buf_index || sqe->personality))
254 		return -EINVAL;
255 
256 	msg->src_file = NULL;
257 	msg->user_data = READ_ONCE(sqe->off);
258 	msg->len = READ_ONCE(sqe->len);
259 	msg->cmd = READ_ONCE(sqe->addr);
260 	msg->src_fd = READ_ONCE(sqe->addr3);
261 	msg->dst_fd = READ_ONCE(sqe->file_index);
262 	msg->flags = READ_ONCE(sqe->msg_ring_flags);
263 	if (msg->flags & ~IORING_MSG_RING_MASK)
264 		return -EINVAL;
265 
266 	return 0;
267 }
268 
io_msg_ring(struct io_kiocb * req,unsigned int issue_flags)269 int io_msg_ring(struct io_kiocb *req, unsigned int issue_flags)
270 {
271 	struct io_msg *msg = io_kiocb_to_cmd(req, struct io_msg);
272 	int ret;
273 
274 	ret = -EBADFD;
275 	if (!io_is_uring_fops(req->file))
276 		goto done;
277 
278 	switch (msg->cmd) {
279 	case IORING_MSG_DATA:
280 		ret = io_msg_ring_data(req, issue_flags);
281 		break;
282 	case IORING_MSG_SEND_FD:
283 		ret = io_msg_send_fd(req, issue_flags);
284 		break;
285 	default:
286 		ret = -EINVAL;
287 		break;
288 	}
289 
290 done:
291 	if (ret < 0) {
292 		if (ret == -EAGAIN || ret == IOU_ISSUE_SKIP_COMPLETE)
293 			return ret;
294 		req_set_fail(req);
295 	}
296 	io_req_set_res(req, ret, 0);
297 	return IOU_OK;
298 }
299