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/export.h>
26 #include <linux/ioprio.h>
27 #include <linux/cred.h>
28 #include <linux/blkdev.h>
29 #include <linux/capability.h>
30 #include <linux/sched/user.h>
31 #include <linux/sched/task.h>
32 #include <linux/syscalls.h>
33 #include <linux/security.h>
34 #include <linux/pid_namespace.h>
35
set_task_ioprio(struct task_struct * task,int ioprio)36 int set_task_ioprio(struct task_struct *task, int ioprio)
37 {
38 int err;
39 struct io_context *ioc;
40 const struct cred *cred = current_cred(), *tcred;
41
42 rcu_read_lock();
43 tcred = __task_cred(task);
44 if (!uid_eq(tcred->uid, cred->euid) &&
45 !uid_eq(tcred->uid, cred->uid) && !capable(CAP_SYS_NICE)) {
46 rcu_read_unlock();
47 return -EPERM;
48 }
49 rcu_read_unlock();
50
51 err = security_task_setioprio(task, ioprio);
52 if (err)
53 return err;
54
55 ioc = get_task_io_context(task, GFP_ATOMIC, NUMA_NO_NODE);
56 if (ioc) {
57 ioc->ioprio = ioprio;
58 put_io_context(ioc);
59 }
60
61 return err;
62 }
63 EXPORT_SYMBOL_GPL(set_task_ioprio);
64
ioprio_check_cap(int ioprio)65 int ioprio_check_cap(int ioprio)
66 {
67 int class = IOPRIO_PRIO_CLASS(ioprio);
68 int data = IOPRIO_PRIO_DATA(ioprio);
69
70 switch (class) {
71 case IOPRIO_CLASS_RT:
72 if (!capable(CAP_SYS_NICE) && !capable(CAP_SYS_ADMIN))
73 return -EPERM;
74 fallthrough;
75 /* 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 return 0;
92 }
93
SYSCALL_DEFINE3(ioprio_set,int,which,int,who,int,ioprio)94 SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio)
95 {
96 struct task_struct *p, *g;
97 struct user_struct *user;
98 struct pid *pgrp;
99 kuid_t uid;
100 int ret;
101
102 ret = ioprio_check_cap(ioprio);
103 if (ret)
104 return ret;
105
106 ret = -ESRCH;
107 rcu_read_lock();
108 switch (which) {
109 case IOPRIO_WHO_PROCESS:
110 if (!who)
111 p = current;
112 else
113 p = find_task_by_vpid(who);
114 if (p)
115 ret = set_task_ioprio(p, ioprio);
116 break;
117 case IOPRIO_WHO_PGRP:
118 if (!who)
119 pgrp = task_pgrp(current);
120 else
121 pgrp = find_vpid(who);
122 do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
123 ret = set_task_ioprio(p, ioprio);
124 if (ret)
125 break;
126 } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
127 break;
128 case IOPRIO_WHO_USER:
129 uid = make_kuid(current_user_ns(), who);
130 if (!uid_valid(uid))
131 break;
132 if (!who)
133 user = current_user();
134 else
135 user = find_user(uid);
136
137 if (!user)
138 break;
139
140 for_each_process_thread(g, p) {
141 if (!uid_eq(task_uid(p), uid) ||
142 !task_pid_vnr(p))
143 continue;
144 ret = set_task_ioprio(p, ioprio);
145 if (ret)
146 goto free_uid;
147 }
148 free_uid:
149 if (who)
150 free_uid(user);
151 break;
152 default:
153 ret = -EINVAL;
154 }
155
156 rcu_read_unlock();
157 return ret;
158 }
159
get_task_ioprio(struct task_struct * p)160 static int get_task_ioprio(struct task_struct *p)
161 {
162 int ret;
163
164 ret = security_task_getioprio(p);
165 if (ret)
166 goto out;
167 ret = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, IOPRIO_NORM);
168 task_lock(p);
169 if (p->io_context)
170 ret = p->io_context->ioprio;
171 task_unlock(p);
172 out:
173 return ret;
174 }
175
ioprio_best(unsigned short aprio,unsigned short bprio)176 int ioprio_best(unsigned short aprio, unsigned short bprio)
177 {
178 if (!ioprio_valid(aprio))
179 aprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM);
180 if (!ioprio_valid(bprio))
181 bprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM);
182
183 return min(aprio, bprio);
184 }
185
SYSCALL_DEFINE2(ioprio_get,int,which,int,who)186 SYSCALL_DEFINE2(ioprio_get, int, which, int, who)
187 {
188 struct task_struct *g, *p;
189 struct user_struct *user;
190 struct pid *pgrp;
191 kuid_t uid;
192 int ret = -ESRCH;
193 int tmpio;
194
195 rcu_read_lock();
196 switch (which) {
197 case IOPRIO_WHO_PROCESS:
198 if (!who)
199 p = current;
200 else
201 p = find_task_by_vpid(who);
202 if (p)
203 ret = get_task_ioprio(p);
204 break;
205 case IOPRIO_WHO_PGRP:
206 if (!who)
207 pgrp = task_pgrp(current);
208 else
209 pgrp = find_vpid(who);
210 do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
211 tmpio = get_task_ioprio(p);
212 if (tmpio < 0)
213 continue;
214 if (ret == -ESRCH)
215 ret = tmpio;
216 else
217 ret = ioprio_best(ret, tmpio);
218 } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
219 break;
220 case IOPRIO_WHO_USER:
221 uid = make_kuid(current_user_ns(), who);
222 if (!who)
223 user = current_user();
224 else
225 user = find_user(uid);
226
227 if (!user)
228 break;
229
230 for_each_process_thread(g, p) {
231 if (!uid_eq(task_uid(p), user->uid) ||
232 !task_pid_vnr(p))
233 continue;
234 tmpio = get_task_ioprio(p);
235 if (tmpio < 0)
236 continue;
237 if (ret == -ESRCH)
238 ret = tmpio;
239 else
240 ret = ioprio_best(ret, tmpio);
241 }
242
243 if (who)
244 free_uid(user);
245 break;
246 default:
247 ret = -EINVAL;
248 }
249
250 rcu_read_unlock();
251 return ret;
252 }
253
