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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * fs/ioprio.c
4 *
5 * Copyright (C) 2004 Jens Axboe <axboe@kernel.dk>
6 *
7 * Helper functions for setting/querying io priorities of processes. The
8 * system calls closely mimmick getpriority/setpriority, see the man page for
9 * those. The prio argument is a composite of prio class and prio data, where
10 * the data argument has meaning within that class. The standard scheduling
11 * classes have 8 distinct prio levels, with 0 being the highest prio and 7
12 * being the lowest.
13 *
14 * IOW, setting BE scheduling class with prio 2 is done ala:
15 *
16 * unsigned int prio = (IOPRIO_CLASS_BE << IOPRIO_CLASS_SHIFT) | 2;
17 *
18 * ioprio_set(PRIO_PROCESS, pid, prio);
19 *
20 * See also Documentation/block/ioprio.rst
21 *
22 */
23#include <linux/gfp.h>
24#include <linux/kernel.h>
25#include <linux/ioprio.h>
26#include <linux/cred.h>
27#include <linux/blkdev.h>
28#include <linux/capability.h>
29#include <linux/syscalls.h>
30#include <linux/security.h>
31#include <linux/pid_namespace.h>
32
33int ioprio_check_cap(int ioprio)
34{
35 int class = IOPRIO_PRIO_CLASS(ioprio);
36 int data = IOPRIO_PRIO_DATA(ioprio);
37
38 switch (class) {
39 case IOPRIO_CLASS_RT:
40 /*
41 * Originally this only checked for CAP_SYS_ADMIN,
42 * which was implicitly allowed for pid 0 by security
43 * modules such as SELinux. Make sure we check
44 * CAP_SYS_ADMIN first to avoid a denial/avc for
45 * possibly missing CAP_SYS_NICE permission.
46 */
47 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_NICE))
48 return -EPERM;
49 fallthrough;
50 /* rt has prio field too */
51 case IOPRIO_CLASS_BE:
52 if (data >= IOPRIO_NR_LEVELS || data < 0)
53 return -EINVAL;
54 break;
55 case IOPRIO_CLASS_IDLE:
56 break;
57 case IOPRIO_CLASS_NONE:
58 if (data)
59 return -EINVAL;
60 break;
61 default:
62 return -EINVAL;
63 }
64
65 return 0;
66}
67
68SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio)
69{
70 struct task_struct *p, *g;
71 struct user_struct *user;
72 struct pid *pgrp;
73 kuid_t uid;
74 int ret;
75
76 ret = ioprio_check_cap(ioprio);
77 if (ret)
78 return ret;
79
80 ret = -ESRCH;
81 rcu_read_lock();
82 switch (which) {
83 case IOPRIO_WHO_PROCESS:
84 if (!who)
85 p = current;
86 else
87 p = find_task_by_vpid(who);
88 if (p)
89 ret = set_task_ioprio(p, ioprio);
90 break;
91 case IOPRIO_WHO_PGRP:
92 if (!who)
93 pgrp = task_pgrp(current);
94 else
95 pgrp = find_vpid(who);
96
97 read_lock(&tasklist_lock);
98 do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
99 ret = set_task_ioprio(p, ioprio);
100 if (ret) {
101 read_unlock(&tasklist_lock);
102 goto out;
103 }
104 } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
105 read_unlock(&tasklist_lock);
106
107 break;
108 case IOPRIO_WHO_USER:
109 uid = make_kuid(current_user_ns(), who);
110 if (!uid_valid(uid))
111 break;
112 if (!who)
113 user = current_user();
114 else
115 user = find_user(uid);
116
117 if (!user)
118 break;
119
120 for_each_process_thread(g, p) {
121 if (!uid_eq(task_uid(p), uid) ||
122 !task_pid_vnr(p))
123 continue;
124 ret = set_task_ioprio(p, ioprio);
125 if (ret)
126 goto free_uid;
127 }
128free_uid:
129 if (who)
130 free_uid(user);
131 break;
132 default:
133 ret = -EINVAL;
134 }
135
136out:
137 rcu_read_unlock();
138 return ret;
139}
140
141/*
142 * If the task has set an I/O priority, use that. Otherwise, return
143 * the default I/O priority.
144 *
145 * Expected to be called for current task or with task_lock() held to keep
146 * io_context stable.
147 */
148int __get_task_ioprio(struct task_struct *p)
149{
150 struct io_context *ioc = p->io_context;
151 int prio;
152
153 if (p != current)
154 lockdep_assert_held(&p->alloc_lock);
155 if (ioc)
156 prio = ioc->ioprio;
157 else
158 prio = IOPRIO_DEFAULT;
159
160 if (IOPRIO_PRIO_CLASS(prio) == IOPRIO_CLASS_NONE)
161 prio = IOPRIO_PRIO_VALUE(task_nice_ioclass(p),
162 task_nice_ioprio(p));
163 return prio;
164}
165EXPORT_SYMBOL_GPL(__get_task_ioprio);
166
167static int get_task_ioprio(struct task_struct *p)
168{
169 int ret;
170
171 ret = security_task_getioprio(p);
172 if (ret)
173 goto out;
174 task_lock(p);
175 ret = __get_task_ioprio(p);
176 task_unlock(p);
177out:
178 return ret;
179}
180
181/*
182 * Return raw IO priority value as set by userspace. We use this for
183 * ioprio_get(pid, IOPRIO_WHO_PROCESS) so that we keep historical behavior and
184 * also so that userspace can distinguish unset IO priority (which just gets
185 * overriden based on task's nice value) from IO priority set to some value.
186 */
187static int get_task_raw_ioprio(struct task_struct *p)
188{
189 int ret;
190
191 ret = security_task_getioprio(p);
192 if (ret)
193 goto out;
194 task_lock(p);
195 if (p->io_context)
196 ret = p->io_context->ioprio;
197 else
198 ret = IOPRIO_DEFAULT;
199 task_unlock(p);
200out:
201 return ret;
202}
203
204static int ioprio_best(unsigned short aprio, unsigned short bprio)
205{
206 return min(aprio, bprio);
207}
208
209SYSCALL_DEFINE2(ioprio_get, int, which, int, who)
210{
211 struct task_struct *g, *p;
212 struct user_struct *user;
213 struct pid *pgrp;
214 kuid_t uid;
215 int ret = -ESRCH;
216 int tmpio;
217
218 rcu_read_lock();
219 switch (which) {
220 case IOPRIO_WHO_PROCESS:
221 if (!who)
222 p = current;
223 else
224 p = find_task_by_vpid(who);
225 if (p)
226 ret = get_task_raw_ioprio(p);
227 break;
228 case IOPRIO_WHO_PGRP:
229 if (!who)
230 pgrp = task_pgrp(current);
231 else
232 pgrp = find_vpid(who);
233 read_lock(&tasklist_lock);
234 do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
235 tmpio = get_task_ioprio(p);
236 if (tmpio < 0)
237 continue;
238 if (ret == -ESRCH)
239 ret = tmpio;
240 else
241 ret = ioprio_best(ret, tmpio);
242 } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
243 read_unlock(&tasklist_lock);
244
245 break;
246 case IOPRIO_WHO_USER:
247 uid = make_kuid(current_user_ns(), who);
248 if (!who)
249 user = current_user();
250 else
251 user = find_user(uid);
252
253 if (!user)
254 break;
255
256 for_each_process_thread(g, p) {
257 if (!uid_eq(task_uid(p), user->uid) ||
258 !task_pid_vnr(p))
259 continue;
260 tmpio = get_task_ioprio(p);
261 if (tmpio < 0)
262 continue;
263 if (ret == -ESRCH)
264 ret = tmpio;
265 else
266 ret = ioprio_best(ret, tmpio);
267 }
268
269 if (who)
270 free_uid(user);
271 break;
272 default:
273 ret = -EINVAL;
274 }
275
276 rcu_read_unlock();
277 return ret;
278}
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * fs/ioprio.c
4 *
5 * Copyright (C) 2004 Jens Axboe <axboe@kernel.dk>
6 *
7 * Helper functions for setting/querying io priorities of processes. The
8 * system calls closely mimmick getpriority/setpriority, see the man page for
9 * those. The prio argument is a composite of prio class and prio data, where
10 * the data argument has meaning within that class. The standard scheduling
11 * classes have 8 distinct prio levels, with 0 being the highest prio and 7
12 * being the lowest.
13 *
14 * IOW, setting BE scheduling class with prio 2 is done ala:
15 *
16 * unsigned int prio = (IOPRIO_CLASS_BE << IOPRIO_CLASS_SHIFT) | 2;
17 *
18 * ioprio_set(PRIO_PROCESS, pid, prio);
19 *
20 * See also Documentation/block/ioprio.rst
21 *
22 */
23#include <linux/gfp.h>
24#include <linux/kernel.h>
25#include <linux/ioprio.h>
26#include <linux/cred.h>
27#include <linux/blkdev.h>
28#include <linux/capability.h>
29#include <linux/syscalls.h>
30#include <linux/security.h>
31#include <linux/pid_namespace.h>
32
33int ioprio_check_cap(int ioprio)
34{
35 int class = IOPRIO_PRIO_CLASS(ioprio);
36 int level = IOPRIO_PRIO_LEVEL(ioprio);
37
38 switch (class) {
39 case IOPRIO_CLASS_RT:
40 /*
41 * Originally this only checked for CAP_SYS_ADMIN,
42 * which was implicitly allowed for pid 0 by security
43 * modules such as SELinux. Make sure we check
44 * CAP_SYS_ADMIN first to avoid a denial/avc for
45 * possibly missing CAP_SYS_NICE permission.
46 */
47 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_NICE))
48 return -EPERM;
49 fallthrough;
50 /* rt has prio field too */
51 case IOPRIO_CLASS_BE:
52 if (level >= IOPRIO_NR_LEVELS)
53 return -EINVAL;
54 break;
55 case IOPRIO_CLASS_IDLE:
56 break;
57 case IOPRIO_CLASS_NONE:
58 if (level)
59 return -EINVAL;
60 break;
61 case IOPRIO_CLASS_INVALID:
62 default:
63 return -EINVAL;
64 }
65
66 return 0;
67}
68
69SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio)
70{
71 struct task_struct *p, *g;
72 struct user_struct *user;
73 struct pid *pgrp;
74 kuid_t uid;
75 int ret;
76
77 ret = ioprio_check_cap(ioprio);
78 if (ret)
79 return ret;
80
81 ret = -ESRCH;
82 rcu_read_lock();
83 switch (which) {
84 case IOPRIO_WHO_PROCESS:
85 if (!who)
86 p = current;
87 else
88 p = find_task_by_vpid(who);
89 if (p)
90 ret = set_task_ioprio(p, ioprio);
91 break;
92 case IOPRIO_WHO_PGRP:
93 if (!who)
94 pgrp = task_pgrp(current);
95 else
96 pgrp = find_vpid(who);
97
98 read_lock(&tasklist_lock);
99 do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
100 ret = set_task_ioprio(p, ioprio);
101 if (ret) {
102 read_unlock(&tasklist_lock);
103 goto out;
104 }
105 } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
106 read_unlock(&tasklist_lock);
107
108 break;
109 case IOPRIO_WHO_USER:
110 uid = make_kuid(current_user_ns(), who);
111 if (!uid_valid(uid))
112 break;
113 if (!who)
114 user = current_user();
115 else
116 user = find_user(uid);
117
118 if (!user)
119 break;
120
121 for_each_process_thread(g, p) {
122 if (!uid_eq(task_uid(p), uid) ||
123 !task_pid_vnr(p))
124 continue;
125 ret = set_task_ioprio(p, ioprio);
126 if (ret)
127 goto free_uid;
128 }
129free_uid:
130 if (who)
131 free_uid(user);
132 break;
133 default:
134 ret = -EINVAL;
135 }
136
137out:
138 rcu_read_unlock();
139 return ret;
140}
141
142static int get_task_ioprio(struct task_struct *p)
143{
144 int ret;
145
146 ret = security_task_getioprio(p);
147 if (ret)
148 goto out;
149 task_lock(p);
150 ret = __get_task_ioprio(p);
151 task_unlock(p);
152out:
153 return ret;
154}
155
156/*
157 * Return raw IO priority value as set by userspace. We use this for
158 * ioprio_get(pid, IOPRIO_WHO_PROCESS) so that we keep historical behavior and
159 * also so that userspace can distinguish unset IO priority (which just gets
160 * overriden based on task's nice value) from IO priority set to some value.
161 */
162static int get_task_raw_ioprio(struct task_struct *p)
163{
164 int ret;
165
166 ret = security_task_getioprio(p);
167 if (ret)
168 goto out;
169 task_lock(p);
170 if (p->io_context)
171 ret = p->io_context->ioprio;
172 else
173 ret = IOPRIO_DEFAULT;
174 task_unlock(p);
175out:
176 return ret;
177}
178
179static int ioprio_best(unsigned short aprio, unsigned short bprio)
180{
181 return min(aprio, bprio);
182}
183
184SYSCALL_DEFINE2(ioprio_get, int, which, int, who)
185{
186 struct task_struct *g, *p;
187 struct user_struct *user;
188 struct pid *pgrp;
189 kuid_t uid;
190 int ret = -ESRCH;
191 int tmpio;
192
193 rcu_read_lock();
194 switch (which) {
195 case IOPRIO_WHO_PROCESS:
196 if (!who)
197 p = current;
198 else
199 p = find_task_by_vpid(who);
200 if (p)
201 ret = get_task_raw_ioprio(p);
202 break;
203 case IOPRIO_WHO_PGRP:
204 if (!who)
205 pgrp = task_pgrp(current);
206 else
207 pgrp = find_vpid(who);
208 read_lock(&tasklist_lock);
209 do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
210 tmpio = get_task_ioprio(p);
211 if (tmpio < 0)
212 continue;
213 if (ret == -ESRCH)
214 ret = tmpio;
215 else
216 ret = ioprio_best(ret, tmpio);
217 } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
218 read_unlock(&tasklist_lock);
219
220 break;
221 case IOPRIO_WHO_USER:
222 uid = make_kuid(current_user_ns(), who);
223 if (!who)
224 user = current_user();
225 else
226 user = find_user(uid);
227
228 if (!user)
229 break;
230
231 for_each_process_thread(g, p) {
232 if (!uid_eq(task_uid(p), user->uid) ||
233 !task_pid_vnr(p))
234 continue;
235 tmpio = get_task_ioprio(p);
236 if (tmpio < 0)
237 continue;
238 if (ret == -ESRCH)
239 ret = tmpio;
240 else
241 ret = ioprio_best(ret, tmpio);
242 }
243
244 if (who)
245 free_uid(user);
246 break;
247 default:
248 ret = -EINVAL;
249 }
250
251 rcu_read_unlock();
252 return ret;
253}