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_NR_LEVELS || data < 0)
  78                                 return -EINVAL;
  79                         break;
  80                 case IOPRIO_CLASS_IDLE:
  81                         break;
  82                 case IOPRIO_CLASS_NONE:
  83                         if (data)
  84                                 return -EINVAL;
  85                         break;
  86                 default:
  87                         return -EINVAL;
  88         }
  89
  90         return 0;
  91 }
  92
  93 SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio)
  94 {
  95         struct task_struct *p, *g;
  96         struct user_struct *user;
  97         struct pid *pgrp;
  98         kuid_t uid;
  99         int ret;
 100
 101         ret = ioprio_check_cap(ioprio);
 102         if (ret)
 103                 return ret;
 104
 105         ret = -ESRCH;
 106         rcu_read_lock();
 107         switch (which) {
 108                 case IOPRIO_WHO_PROCESS:
 109                         if (!who)
 110                                 p = current;
 111                         else
 112                                 p = find_task_by_vpid(who);
 113                         if (p)
 114                                 ret = set_task_ioprio(p, ioprio);
 115                         break;
 116                 case IOPRIO_WHO_PGRP:
 117                         if (!who)
 118                                 pgrp = task_pgrp(current);
 119                         else
 120                                 pgrp = find_vpid(who);
 121
 122                         read_lock(&tasklist_lock);
 123                         do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
 124                                 ret = set_task_ioprio(p, ioprio);
 125                                 if (ret) {
 126                                         read_unlock(&tasklist_lock);
 127                                         goto out;
 128                                 }
 129                         } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
 130                         read_unlock(&tasklist_lock);
 131
 132                         break;
 133                 case IOPRIO_WHO_USER:
 134                         uid = make_kuid(current_user_ns(), who);
 135                         if (!uid_valid(uid))
 136                                 break;
 137                         if (!who)
 138                                 user = current_user();
 139                         else
 140                                 user = find_user(uid);
 141
 142                         if (!user)
 143                                 break;
 144
 145                         for_each_process_thread(g, p) {
 146                                 if (!uid_eq(task_uid(p), uid) ||
 147                                     !task_pid_vnr(p))
 148                                         continue;
 149                                 ret = set_task_ioprio(p, ioprio);
 150                                 if (ret)
 151                                         goto free_uid;
 152                         }
 153 free_uid:
 154                         if (who)
 155                                 free_uid(user);
 156                         break;
 157                 default:
 158                         ret = -EINVAL;
 159         }
 160
 161 out:
 162         rcu_read_unlock();
 163         return ret;
 164 }
 165
 166 static int get_task_ioprio(struct task_struct *p)
 167 {
 168         int ret;
 169
 170         ret = security_task_getioprio(p);
 171         if (ret)
 172                 goto out;
 173         ret = IOPRIO_DEFAULT;
 174         task_lock(p);
 175         if (p->io_context)
 176                 ret = p->io_context->ioprio;
 177         task_unlock(p);
 178 out:
 179         return ret;
 180 }
 181
 182 int ioprio_best(unsigned short aprio, unsigned short bprio)
 183 {
 184         if (!ioprio_valid(aprio))
 185                 aprio = IOPRIO_DEFAULT;
 186         if (!ioprio_valid(bprio))
 187                 bprio = IOPRIO_DEFAULT;
 188
 189         return min(aprio, bprio);
 190 }
 191
 192 SYSCALL_DEFINE2(ioprio_get, int, which, int, who)
 193 {
 194         struct task_struct *g, *p;
 195         struct user_struct *user;
 196         struct pid *pgrp;
 197         kuid_t uid;
 198         int ret = -ESRCH;
 199         int tmpio;
 200
 201         rcu_read_lock();
 202         switch (which) {
 203                 case IOPRIO_WHO_PROCESS:
 204                         if (!who)
 205                                 p = current;
 206                         else
 207                                 p = find_task_by_vpid(who);
 208                         if (p)
 209                                 ret = get_task_ioprio(p);
 210                         break;
 211                 case IOPRIO_WHO_PGRP:
 212                         if (!who)
 213                                 pgrp = task_pgrp(current);
 214                         else
 215                                 pgrp = find_vpid(who);
 216                         do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
 217                                 tmpio = get_task_ioprio(p);
 218                                 if (tmpio < 0)
 219                                         continue;
 220                                 if (ret == -ESRCH)
 221                                         ret = tmpio;
 222                                 else
 223                                         ret = ioprio_best(ret, tmpio);
 224                         } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
 225                         break;
 226                 case IOPRIO_WHO_USER:
 227                         uid = make_kuid(current_user_ns(), who);
 228                         if (!who)
 229                                 user = current_user();
 230                         else
 231                                 user = find_user(uid);
 232
 233                         if (!user)
 234                                 break;
 235
 236                         for_each_process_thread(g, p) {
 237                                 if (!uid_eq(task_uid(p), user->uid) ||
 238                                     !task_pid_vnr(p))
 239                                         continue;
 240                                 tmpio = get_task_ioprio(p);
 241                                 if (tmpio < 0)
 242                                         continue;
 243                                 if (ret == -ESRCH)
 244                                         ret = tmpio;
 245                                 else
 246                                         ret = ioprio_best(ret, tmpio);
 247                         }
 248
 249                         if (who)
 250                                 free_uid(user);
 251                         break;
 252                 default:
 253                         ret = -EINVAL;
 254         }
 255
 256         rcu_read_unlock();
 257         return ret;
 258 }