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1// SPDX-License-Identifier: GPL-2.02/*3 * fs/ioprio.c4 *5 * Copyright (C) 2004 Jens Axboe <axboe@kernel.dk>6 *7 * Helper functions for setting/querying io priorities of processes. The8 * system calls closely mimmick getpriority/setpriority, see the man page for9 * those. The prio argument is a composite of prio class and prio data, where10 * the data argument has meaning within that class. The standard scheduling11 * classes have 8 distinct prio levels, with 0 being the highest prio and 712 * 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.rst21 *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 security43 * modules such as SELinux. Make sure we check44 * CAP_SYS_ADMIN first to avoid a denial/avc for45 * 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 else88 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 else96 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 else116 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 for158 * ioprio_get(pid, IOPRIO_WHO_PROCESS) so that we keep historical behavior and159 * also so that userspace can distinguish unset IO priority (which just gets160 * 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 else173 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 else199 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 else207 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 else216 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 else226 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 else241 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}254