| 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 | int 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 | |
| 69 | 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 | 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 | } |
| 129 | free_uid: |
| 130 | if (who) |
| 131 | free_uid(user); |
| 132 | break; |
| 133 | default: |
| 134 | ret = -EINVAL; |
| 135 | } |
| 136 | |
| 137 | out: |
| 138 | rcu_read_unlock(); |
| 139 | return ret; |
| 140 | } |
| 141 | |
| 142 | static 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); |
| 152 | out: |
| 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 | */ |
| 162 | static 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); |
| 175 | out: |
| 176 | return ret; |
| 177 | } |
| 178 | |
| 179 | static int ioprio_best(unsigned short aprio, unsigned short bprio) |
| 180 | { |
| 181 | return min(aprio, bprio); |
| 182 | } |
| 183 | |
| 184 | SYSCALL_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 | } |