Line data Source code
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 :
33 0 : int ioprio_check_cap(int ioprio)
34 : {
35 0 : int class = IOPRIO_PRIO_CLASS(ioprio);
36 0 : int level = IOPRIO_PRIO_LEVEL(ioprio);
37 :
38 0 : 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 0 : 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 0 : if (level >= IOPRIO_NR_LEVELS)
53 : return -EINVAL;
54 : break;
55 : case IOPRIO_CLASS_IDLE:
56 : break;
57 : case IOPRIO_CLASS_NONE:
58 0 : if (level)
59 : return -EINVAL;
60 : break;
61 : case IOPRIO_CLASS_INVALID:
62 : default:
63 : return -EINVAL;
64 : }
65 :
66 : return 0;
67 : }
68 :
69 0 : SYSCALL_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 0 : ret = ioprio_check_cap(ioprio);
78 0 : if (ret)
79 0 : return ret;
80 :
81 0 : ret = -ESRCH;
82 : rcu_read_lock();
83 0 : switch (which) {
84 : case IOPRIO_WHO_PROCESS:
85 0 : if (!who)
86 0 : p = current;
87 : else
88 0 : p = find_task_by_vpid(who);
89 0 : if (p)
90 0 : ret = set_task_ioprio(p, ioprio);
91 : break;
92 : case IOPRIO_WHO_PGRP:
93 0 : if (!who)
94 0 : pgrp = task_pgrp(current);
95 : else
96 0 : pgrp = find_vpid(who);
97 :
98 0 : read_lock(&tasklist_lock);
99 0 : do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
100 0 : ret = set_task_ioprio(p, ioprio);
101 0 : if (ret) {
102 0 : read_unlock(&tasklist_lock);
103 0 : goto out;
104 : }
105 0 : } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
106 0 : read_unlock(&tasklist_lock);
107 :
108 0 : break;
109 : case IOPRIO_WHO_USER:
110 0 : uid = make_kuid(current_user_ns(), who);
111 0 : if (!uid_valid(uid))
112 : break;
113 0 : if (!who)
114 0 : user = current_user();
115 : else
116 0 : user = find_user(uid);
117 :
118 0 : if (!user)
119 : break;
120 :
121 0 : for_each_process_thread(g, p) {
122 0 : if (!uid_eq(task_uid(p), uid) ||
123 0 : !task_pid_vnr(p))
124 0 : continue;
125 0 : ret = set_task_ioprio(p, ioprio);
126 0 : if (ret)
127 : goto free_uid;
128 : }
129 : free_uid:
130 0 : if (who)
131 0 : free_uid(user);
132 : break;
133 : default:
134 : ret = -EINVAL;
135 : }
136 :
137 : out:
138 : rcu_read_unlock();
139 0 : return ret;
140 : }
141 :
142 : /*
143 : * If the task has set an I/O priority, use that. Otherwise, return
144 : * the default I/O priority.
145 : *
146 : * Expected to be called for current task or with task_lock() held to keep
147 : * io_context stable.
148 : */
149 0 : int __get_task_ioprio(struct task_struct *p)
150 : {
151 0 : struct io_context *ioc = p->io_context;
152 : int prio;
153 :
154 0 : if (p != current)
155 : lockdep_assert_held(&p->alloc_lock);
156 0 : if (ioc)
157 0 : prio = ioc->ioprio;
158 : else
159 : prio = IOPRIO_DEFAULT;
160 :
161 0 : if (IOPRIO_PRIO_CLASS(prio) == IOPRIO_CLASS_NONE)
162 0 : prio = IOPRIO_PRIO_VALUE(task_nice_ioclass(p),
163 : task_nice_ioprio(p));
164 0 : return prio;
165 : }
166 : EXPORT_SYMBOL_GPL(__get_task_ioprio);
167 :
168 : static int get_task_ioprio(struct task_struct *p)
169 : {
170 : int ret;
171 :
172 0 : ret = security_task_getioprio(p);
173 : if (ret)
174 : goto out;
175 0 : task_lock(p);
176 0 : ret = __get_task_ioprio(p);
177 0 : task_unlock(p);
178 : out:
179 : return ret;
180 : }
181 :
182 : /*
183 : * Return raw IO priority value as set by userspace. We use this for
184 : * ioprio_get(pid, IOPRIO_WHO_PROCESS) so that we keep historical behavior and
185 : * also so that userspace can distinguish unset IO priority (which just gets
186 : * overriden based on task's nice value) from IO priority set to some value.
187 : */
188 : static int get_task_raw_ioprio(struct task_struct *p)
189 : {
190 : int ret;
191 :
192 0 : ret = security_task_getioprio(p);
193 : if (ret)
194 : goto out;
195 0 : task_lock(p);
196 0 : if (p->io_context)
197 0 : ret = p->io_context->ioprio;
198 : else
199 : ret = IOPRIO_DEFAULT;
200 0 : task_unlock(p);
201 : out:
202 : return ret;
203 : }
204 :
205 : static int ioprio_best(unsigned short aprio, unsigned short bprio)
206 : {
207 0 : return min(aprio, bprio);
208 : }
209 :
210 0 : SYSCALL_DEFINE2(ioprio_get, int, which, int, who)
211 : {
212 : struct task_struct *g, *p;
213 : struct user_struct *user;
214 : struct pid *pgrp;
215 : kuid_t uid;
216 0 : int ret = -ESRCH;
217 : int tmpio;
218 :
219 : rcu_read_lock();
220 0 : switch (which) {
221 : case IOPRIO_WHO_PROCESS:
222 0 : if (!who)
223 0 : p = current;
224 : else
225 0 : p = find_task_by_vpid(who);
226 0 : if (p)
227 0 : ret = get_task_raw_ioprio(p);
228 : break;
229 : case IOPRIO_WHO_PGRP:
230 0 : if (!who)
231 0 : pgrp = task_pgrp(current);
232 : else
233 0 : pgrp = find_vpid(who);
234 0 : read_lock(&tasklist_lock);
235 0 : do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
236 0 : tmpio = get_task_ioprio(p);
237 0 : if (tmpio < 0)
238 0 : continue;
239 0 : if (ret == -ESRCH)
240 : ret = tmpio;
241 : else
242 0 : ret = ioprio_best(ret, tmpio);
243 0 : } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
244 0 : read_unlock(&tasklist_lock);
245 :
246 0 : break;
247 : case IOPRIO_WHO_USER:
248 0 : uid = make_kuid(current_user_ns(), who);
249 0 : if (!who)
250 0 : user = current_user();
251 : else
252 0 : user = find_user(uid);
253 :
254 0 : if (!user)
255 : break;
256 :
257 0 : for_each_process_thread(g, p) {
258 0 : if (!uid_eq(task_uid(p), user->uid) ||
259 0 : !task_pid_vnr(p))
260 0 : continue;
261 0 : tmpio = get_task_ioprio(p);
262 0 : if (tmpio < 0)
263 0 : continue;
264 0 : if (ret == -ESRCH)
265 : ret = tmpio;
266 : else
267 0 : ret = ioprio_best(ret, tmpio);
268 : }
269 :
270 0 : if (who)
271 0 : free_uid(user);
272 : break;
273 : default:
274 : ret = -EINVAL;
275 : }
276 :
277 : rcu_read_unlock();
278 0 : return ret;
279 : }
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