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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/*
2 * fs/ioprio.c
3 *
4 * Copyright (C) 2004 Jens Axboe <axboe@kernel.dk>
5 *
6 * Helper functions for setting/querying io priorities of processes. The
7 * system calls closely mimmick getpriority/setpriority, see the man page for
8 * those. The prio argument is a composite of prio class and prio data, where
9 * the data argument has meaning within that class. The standard scheduling
10 * classes have 8 distinct prio levels, with 0 being the highest prio and 7
11 * being the lowest.
12 *
13 * IOW, setting BE scheduling class with prio 2 is done ala:
14 *
15 * unsigned int prio = (IOPRIO_CLASS_BE << IOPRIO_CLASS_SHIFT) | 2;
16 *
17 * ioprio_set(PRIO_PROCESS, pid, prio);
18 *
19 * See also Documentation/block/ioprio.txt
20 *
21 */
22#include <linux/gfp.h>
23#include <linux/kernel.h>
24#include <linux/export.h>
25#include <linux/ioprio.h>
26#include <linux/blkdev.h>
27#include <linux/capability.h>
28#include <linux/syscalls.h>
29#include <linux/security.h>
30#include <linux/pid_namespace.h>
31
32int set_task_ioprio(struct task_struct *task, int ioprio)
33{
34 int err;
35 struct io_context *ioc;
36 const struct cred *cred = current_cred(), *tcred;
37
38 rcu_read_lock();
39 tcred = __task_cred(task);
40 if (!uid_eq(tcred->uid, cred->euid) &&
41 !uid_eq(tcred->uid, cred->uid) && !capable(CAP_SYS_NICE)) {
42 rcu_read_unlock();
43 return -EPERM;
44 }
45 rcu_read_unlock();
46
47 err = security_task_setioprio(task, ioprio);
48 if (err)
49 return err;
50
51 ioc = get_task_io_context(task, GFP_ATOMIC, NUMA_NO_NODE);
52 if (ioc) {
53 ioc->ioprio = ioprio;
54 put_io_context(ioc);
55 }
56
57 return err;
58}
59EXPORT_SYMBOL_GPL(set_task_ioprio);
60
61SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio)
62{
63 int class = IOPRIO_PRIO_CLASS(ioprio);
64 int data = IOPRIO_PRIO_DATA(ioprio);
65 struct task_struct *p, *g;
66 struct user_struct *user;
67 struct pid *pgrp;
68 kuid_t uid;
69 int ret;
70
71 switch (class) {
72 case IOPRIO_CLASS_RT:
73 if (!capable(CAP_SYS_ADMIN))
74 return -EPERM;
75 /* fall through, rt has prio field too */
76 case IOPRIO_CLASS_BE:
77 if (data >= IOPRIO_BE_NR || data < 0)
78 return -EINVAL;
79
80 break;
81 case IOPRIO_CLASS_IDLE:
82 break;
83 case IOPRIO_CLASS_NONE:
84 if (data)
85 return -EINVAL;
86 break;
87 default:
88 return -EINVAL;
89 }
90
91 ret = -ESRCH;
92 rcu_read_lock();
93 switch (which) {
94 case IOPRIO_WHO_PROCESS:
95 if (!who)
96 p = current;
97 else
98 p = find_task_by_vpid(who);
99 if (p)
100 ret = set_task_ioprio(p, ioprio);
101 break;
102 case IOPRIO_WHO_PGRP:
103 if (!who)
104 pgrp = task_pgrp(current);
105 else
106 pgrp = find_vpid(who);
107 do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
108 ret = set_task_ioprio(p, ioprio);
109 if (ret)
110 break;
111 } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
112 break;
113 case IOPRIO_WHO_USER:
114 uid = make_kuid(current_user_ns(), who);
115 if (!uid_valid(uid))
116 break;
117 if (!who)
118 user = current_user();
119 else
120 user = find_user(uid);
121
122 if (!user)
123 break;
124
125 do_each_thread(g, p) {
126 if (!uid_eq(task_uid(p), uid) ||
127 !task_pid_vnr(p))
128 continue;
129 ret = set_task_ioprio(p, ioprio);
130 if (ret)
131 goto free_uid;
132 } while_each_thread(g, p);
133free_uid:
134 if (who)
135 free_uid(user);
136 break;
137 default:
138 ret = -EINVAL;
139 }
140
141 rcu_read_unlock();
142 return ret;
143}
144
145static int get_task_ioprio(struct task_struct *p)
146{
147 int ret;
148
149 ret = security_task_getioprio(p);
150 if (ret)
151 goto out;
152 ret = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, IOPRIO_NORM);
153 if (p->io_context)
154 ret = p->io_context->ioprio;
155out:
156 return ret;
157}
158
159int ioprio_best(unsigned short aprio, unsigned short bprio)
160{
161 unsigned short aclass;
162 unsigned short bclass;
163
164 if (!ioprio_valid(aprio))
165 aprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM);
166 if (!ioprio_valid(bprio))
167 bprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM);
168
169 aclass = IOPRIO_PRIO_CLASS(aprio);
170 bclass = IOPRIO_PRIO_CLASS(bprio);
171 if (aclass == bclass)
172 return min(aprio, bprio);
173 if (aclass > bclass)
174 return bprio;
175 else
176 return aprio;
177}
178
179SYSCALL_DEFINE2(ioprio_get, int, which, int, who)
180{
181 struct task_struct *g, *p;
182 struct user_struct *user;
183 struct pid *pgrp;
184 kuid_t uid;
185 int ret = -ESRCH;
186 int tmpio;
187
188 rcu_read_lock();
189 switch (which) {
190 case IOPRIO_WHO_PROCESS:
191 if (!who)
192 p = current;
193 else
194 p = find_task_by_vpid(who);
195 if (p)
196 ret = get_task_ioprio(p);
197 break;
198 case IOPRIO_WHO_PGRP:
199 if (!who)
200 pgrp = task_pgrp(current);
201 else
202 pgrp = find_vpid(who);
203 do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
204 tmpio = get_task_ioprio(p);
205 if (tmpio < 0)
206 continue;
207 if (ret == -ESRCH)
208 ret = tmpio;
209 else
210 ret = ioprio_best(ret, tmpio);
211 } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
212 break;
213 case IOPRIO_WHO_USER:
214 uid = make_kuid(current_user_ns(), who);
215 if (!who)
216 user = current_user();
217 else
218 user = find_user(uid);
219
220 if (!user)
221 break;
222
223 do_each_thread(g, p) {
224 if (!uid_eq(task_uid(p), user->uid) ||
225 !task_pid_vnr(p))
226 continue;
227 tmpio = get_task_ioprio(p);
228 if (tmpio < 0)
229 continue;
230 if (ret == -ESRCH)
231 ret = tmpio;
232 else
233 ret = ioprio_best(ret, tmpio);
234 } while_each_thread(g, p);
235
236 if (who)
237 free_uid(user);
238 break;
239 default:
240 ret = -EINVAL;
241 }
242
243 rcu_read_unlock();
244 return ret;
245}