block/ioprio.c

   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
  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
  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
  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
 123                         read_lock(&tasklist_lock);
 124                         do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
 125                                 ret = set_task_ioprio(p, ioprio);
 126                                 if (ret) {
 127                                         read_unlock(&tasklist_lock);
 128                                         goto out;
 129                                 }
 130                         } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
 131                         read_unlock(&tasklist_lock);
 132
 133                         break;
 134                 case IOPRIO_WHO_USER:
 135                         uid = make_kuid(current_user_ns(), who);
 136                         if (!uid_valid(uid))
 137                                 break;
 138                         if (!who)
 139                                 user = current_user();
 140                         else
 141                                 user = find_user(uid);
 142
 143                         if (!user)
 144                                 break;
 145
 146                         for_each_process_thread(g, p) {
 147                                 if (!uid_eq(task_uid(p), uid) ||
 148                                     !task_pid_vnr(p))
 149                                         continue;
 150                                 ret = set_task_ioprio(p, ioprio);
 151                                 if (ret)
 152                                         goto free_uid;
 153                         }
 154 free_uid:
 155                         if (who)
 156                                 free_uid(user);
 157                         break;
 158                 default:
 159                         ret = -EINVAL;
 160         }
 161
 162 out:
 163         rcu_read_unlock();
 164         return ret;
 165 }
 166
 167 static 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         ret = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, IOPRIO_NORM);
 175         task_lock(p);
 176         if (p->io_context)
 177                 ret = p->io_context->ioprio;
 178         task_unlock(p);
 179 out:
 180         return ret;
 181 }
 182
 183 int ioprio_best(unsigned short aprio, unsigned short bprio)
 184 {
 185         if (!ioprio_valid(aprio))
 186                 aprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM);
 187         if (!ioprio_valid(bprio))
 188                 bprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM);
 189
 190         return min(aprio, bprio);
 191 }
 192
 193 SYSCALL_DEFINE2(ioprio_get, int, which, int, who)
 194 {
 195         struct task_struct *g, *p;
 196         struct user_struct *user;
 197         struct pid *pgrp;
 198         kuid_t uid;
 199         int ret = -ESRCH;
 200         int tmpio;
 201
 202         rcu_read_lock();
 203         switch (which) {
 204                 case IOPRIO_WHO_PROCESS:
 205                         if (!who)
 206                                 p = current;
 207                         else
 208                                 p = find_task_by_vpid(who);
 209                         if (p)
 210                                 ret = get_task_ioprio(p);
 211                         break;
 212                 case IOPRIO_WHO_PGRP:
 213                         if (!who)
 214                                 pgrp = task_pgrp(current);
 215                         else
 216                                 pgrp = find_vpid(who);
 217                         do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
 218                                 tmpio = get_task_ioprio(p);
 219                                 if (tmpio < 0)
 220                                         continue;
 221                                 if (ret == -ESRCH)
 222                                         ret = tmpio;
 223                                 else
 224                                         ret = ioprio_best(ret, tmpio);
 225                         } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
 226                         break;
 227                 case IOPRIO_WHO_USER:
 228                         uid = make_kuid(current_user_ns(), who);
 229                         if (!who)
 230                                 user = current_user();
 231                         else
 232                                 user = find_user(uid);
 233
 234                         if (!user)
 235                                 break;
 236
 237                         for_each_process_thread(g, p) {
 238                                 if (!uid_eq(task_uid(p), user->uid) ||
 239                                     !task_pid_vnr(p))
 240                                         continue;
 241                                 tmpio = get_task_ioprio(p);
 242                                 if (tmpio < 0)
 243                                         continue;
 244                                 if (ret == -ESRCH)
 245                                         ret = tmpio;
 246                                 else
 247                                         ret = ioprio_best(ret, tmpio);
 248                         }
 249
 250                         if (who)
 251                                 free_uid(user);
 252                         break;
 253                 default:
 254                         ret = -EINVAL;
 255         }
 256
 257         rcu_read_unlock();
 258         return ret;
 259 }