fs/quota.c

   1 /*
   2  * Quota code necessary even when VFS quota support is not compiled
   3  * into the kernel.  The interesting stuff is over in dquot.c, here
   4  * we have symbols for initial quotactl(2) handling, the sysctl(2)
   5  * variables, etc - things needed even when quota support disabled.
   6  */
   7
   8 #include <linux/fs.h>
   9 #include <linux/namei.h>
  10 #include <linux/slab.h>
  11 #include <asm/current.h>
  12 #include <asm/uaccess.h>
  13 #include <linux/kernel.h>
  14 #include <linux/smp_lock.h>
  15 #include <linux/security.h>
  16 #include <linux/syscalls.h>
  17 #include <linux/buffer_head.h>
  18
  19 /* Check validity of quotactl */
  20 static int check_quotactl_valid(struct super_block *sb, int type, int cmd, qid_t id)
  21 {
  22         if (type >= MAXQUOTAS)
  23                 return -EINVAL;
  24         if (!sb && cmd != Q_SYNC)
  25                 return -ENODEV;
  26         /* Is operation supported? */
  27         if (sb && !sb->s_qcop)
  28                 return -ENOSYS;
  29
  30         switch (cmd) {
  31                 case Q_GETFMT:
  32                         break;
  33                 case Q_QUOTAON:
  34                         if (!sb->s_qcop->quota_on)
  35                                 return -ENOSYS;
  36                         break;
  37                 case Q_QUOTAOFF:
  38                         if (!sb->s_qcop->quota_off)
  39                                 return -ENOSYS;
  40                         break;
  41                 case Q_SETINFO:
  42                         if (!sb->s_qcop->set_info)
  43                                 return -ENOSYS;
  44                         break;
  45                 case Q_GETINFO:
  46                         if (!sb->s_qcop->get_info)
  47                                 return -ENOSYS;
  48                         break;
  49                 case Q_SETQUOTA:
  50                         if (!sb->s_qcop->set_dqblk)
  51                                 return -ENOSYS;
  52                         break;
  53                 case Q_GETQUOTA:
  54                         if (!sb->s_qcop->get_dqblk)
  55                                 return -ENOSYS;
  56                         break;
  57                 case Q_SYNC:
  58                         if (sb && !sb->s_qcop->quota_sync)
  59                                 return -ENOSYS;
  60                         break;
  61                 case Q_XQUOTAON:
  62                 case Q_XQUOTAOFF:
  63                 case Q_XQUOTARM:
  64                         if (!sb->s_qcop->set_xstate)
  65                                 return -ENOSYS;
  66                         break;
  67                 case Q_XGETQSTAT:
  68                         if (!sb->s_qcop->get_xstate)
  69                                 return -ENOSYS;
  70                         break;
  71                 case Q_XSETQLIM:
  72                         if (!sb->s_qcop->set_xquota)
  73                                 return -ENOSYS;
  74                         break;
  75                 case Q_XGETQUOTA:
  76                         if (!sb->s_qcop->get_xquota)
  77                                 return -ENOSYS;
  78                         break;
  79                 default:
  80                         return -EINVAL;
  81         }
  82
  83         /* Is quota turned on for commands which need it? */
  84         switch (cmd) {
  85                 case Q_GETFMT:
  86                 case Q_GETINFO:
  87                 case Q_QUOTAOFF:
  88                 case Q_SETINFO:
  89                 case Q_SETQUOTA:
  90                 case Q_GETQUOTA:
  91                         /* This is just informative test so we are satisfied without a lock */
  92                         if (!sb_has_quota_enabled(sb, type))
  93                                 return -ESRCH;
  94         }
  95         /* Check privileges */
  96         if (cmd == Q_GETQUOTA || cmd == Q_XGETQUOTA) {
  97                 if (((type == USRQUOTA && current->euid != id) ||
  98                      (type == GRPQUOTA && !in_egroup_p(id))) &&
  99                     !capable(CAP_SYS_ADMIN))
 100                         return -EPERM;
 101         }
 102         else if (cmd != Q_GETFMT && cmd != Q_SYNC && cmd != Q_GETINFO && cmd != Q_XGETQSTAT)
 103                 if (!capable(CAP_SYS_ADMIN))
 104                         return -EPERM;
 105
 106         return security_quotactl (cmd, type, id, sb);
 107 }
 108
 109 static struct super_block *get_super_to_sync(int type)
 110 {
 111         struct list_head *head;
 112         int cnt, dirty;
 113
 114 restart:
 115         spin_lock(&sb_lock);
 116         list_for_each(head, &super_blocks) {
 117                 struct super_block *sb = list_entry(head, struct super_block, s_list);
 118
 119                 /* This test just improves performance so it needn't be reliable... */
 120                 for (cnt = 0, dirty = 0; cnt < MAXQUOTAS; cnt++)
 121                         if ((type == cnt || type == -1) && sb_has_quota_enabled(sb, cnt)
 122                             && info_any_dirty(&sb_dqopt(sb)->info[cnt]))
 123                                 dirty = 1;
 124                 if (!dirty)
 125                         continue;
 126                 sb->s_count++;
 127                 spin_unlock(&sb_lock);
 128                 down_read(&sb->s_umount);
 129                 if (!sb->s_root) {
 130                         drop_super(sb);
 131                         goto restart;
 132                 }
 133                 return sb;
 134         }
 135         spin_unlock(&sb_lock);
 136         return NULL;
 137 }
 138
 139 static void quota_sync_sb(struct super_block *sb, int type)
 140 {
 141         int cnt;
 142         struct inode *discard[MAXQUOTAS];
 143
 144         sb->s_qcop->quota_sync(sb, type);
 145         /* This is not very clever (and fast) but currently I don't know about
 146          * any other simple way of getting quota data to disk and we must get
 147          * them there for userspace to be visible... */
 148         if (sb->s_op->sync_fs)
 149                 sb->s_op->sync_fs(sb, 1);
 150         sync_blockdev(sb->s_bdev);
 151
 152         /* Now when everything is written we can discard the pagecache so
 153          * that userspace sees the changes. We need i_sem and so we could
 154          * not do it inside dqonoff_sem. Moreover we need to be carefull
 155          * about races with quotaoff() (that is the reason why we have own
 156          * reference to inode). */
 157         down(&sb_dqopt(sb)->dqonoff_sem);
 158         for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
 159                 discard[cnt] = NULL;
 160                 if (type != -1 && cnt != type)
 161                         continue;
 162                 if (!sb_has_quota_enabled(sb, cnt))
 163                         continue;
 164                 discard[cnt] = igrab(sb_dqopt(sb)->files[cnt]);
 165         }
 166         up(&sb_dqopt(sb)->dqonoff_sem);
 167         for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
 168                 if (discard[cnt]) {
 169                         down(&discard[cnt]->i_sem);
 170                         truncate_inode_pages(&discard[cnt]->i_data, 0);
 171                         up(&discard[cnt]->i_sem);
 172                         iput(discard[cnt]);
 173                 }
 174         }
 175 }
 176
 177 void sync_dquots(struct super_block *sb, int type)
 178 {
 179         if (sb) {
 180                 if (sb->s_qcop->quota_sync)
 181                         quota_sync_sb(sb, type);
 182         }
 183         else {
 184                 while ((sb = get_super_to_sync(type)) != NULL) {
 185                         if (sb->s_qcop->quota_sync)
 186                                 quota_sync_sb(sb, type);
 187                         drop_super(sb);
 188                 }
 189         }
 190 }
 191
 192 /* Copy parameters and call proper function */
 193 static int do_quotactl(struct super_block *sb, int type, int cmd, qid_t id, void __user *addr)
 194 {
 195         int ret;
 196
 197         switch (cmd) {
 198                 case Q_QUOTAON: {
 199                         char *pathname;
 200
 201                         if (IS_ERR(pathname = getname(addr)))
 202                                 return PTR_ERR(pathname);
 203                         ret = sb->s_qcop->quota_on(sb, type, id, pathname);
 204                         putname(pathname);
 205                         return ret;
 206                 }
 207                 case Q_QUOTAOFF:
 208                         return sb->s_qcop->quota_off(sb, type);
 209
 210                 case Q_GETFMT: {
 211                         __u32 fmt;
 212
 213                         down_read(&sb_dqopt(sb)->dqptr_sem);
 214                         if (!sb_has_quota_enabled(sb, type)) {
 215                                 up_read(&sb_dqopt(sb)->dqptr_sem);
 216                                 return -ESRCH;
 217                         }
 218                         fmt = sb_dqopt(sb)->info[type].dqi_format->qf_fmt_id;
 219                         up_read(&sb_dqopt(sb)->dqptr_sem);
 220                         if (copy_to_user(addr, &fmt, sizeof(fmt)))
 221                                 return -EFAULT;
 222                         return 0;
 223                 }
 224                 case Q_GETINFO: {
 225                         struct if_dqinfo info;
 226
 227                         if ((ret = sb->s_qcop->get_info(sb, type, &info)))
 228                                 return ret;
 229                         if (copy_to_user(addr, &info, sizeof(info)))
 230                                 return -EFAULT;
 231                         return 0;
 232                 }
 233                 case Q_SETINFO: {
 234                         struct if_dqinfo info;
 235
 236                         if (copy_from_user(&info, addr, sizeof(info)))
 237                                 return -EFAULT;
 238                         return sb->s_qcop->set_info(sb, type, &info);
 239                 }
 240                 case Q_GETQUOTA: {
 241                         struct if_dqblk idq;
 242
 243                         if ((ret = sb->s_qcop->get_dqblk(sb, type, id, &idq)))
 244                                 return ret;
 245                         if (copy_to_user(addr, &idq, sizeof(idq)))
 246                                 return -EFAULT;
 247                         return 0;
 248                 }
 249                 case Q_SETQUOTA: {
 250                         struct if_dqblk idq;
 251
 252                         if (copy_from_user(&idq, addr, sizeof(idq)))
 253                                 return -EFAULT;
 254                         return sb->s_qcop->set_dqblk(sb, type, id, &idq);
 255                 }
 256                 case Q_SYNC:
 257                         sync_dquots(sb, type);
 258                         return 0;
 259
 260                 case Q_XQUOTAON:
 261                 case Q_XQUOTAOFF:
 262                 case Q_XQUOTARM: {
 263                         __u32 flags;
 264
 265                         if (copy_from_user(&flags, addr, sizeof(flags)))
 266                                 return -EFAULT;
 267                         return sb->s_qcop->set_xstate(sb, flags, cmd);
 268                 }
 269                 case Q_XGETQSTAT: {
 270                         struct fs_quota_stat fqs;
 271
 272                         if ((ret = sb->s_qcop->get_xstate(sb, &fqs)))
 273                                 return ret;
 274                         if (copy_to_user(addr, &fqs, sizeof(fqs)))
 275                                 return -EFAULT;
 276                         return 0;
 277                 }
 278                 case Q_XSETQLIM: {
 279                         struct fs_disk_quota fdq;
 280
 281                         if (copy_from_user(&fdq, addr, sizeof(fdq)))
 282                                 return -EFAULT;
 283                        return sb->s_qcop->set_xquota(sb, type, id, &fdq);
 284                 }
 285                 case Q_XGETQUOTA: {
 286                         struct fs_disk_quota fdq;
 287
 288                         if ((ret = sb->s_qcop->get_xquota(sb, type, id, &fdq)))
 289                                 return ret;
 290                         if (copy_to_user(addr, &fdq, sizeof(fdq)))
 291                                 return -EFAULT;
 292                         return 0;
 293                 }
 294                 /* We never reach here unless validity check is broken */
 295                 default:
 296                         BUG();
 297         }
 298         return 0;
 299 }
 300
 301 /*
 302  * This is the system call interface. This communicates with
 303  * the user-level programs. Currently this only supports diskquota
 304  * calls. Maybe we need to add the process quotas etc. in the future,
 305  * but we probably should use rlimits for that.
 306  */
 307 asmlinkage long sys_quotactl(unsigned int cmd, const char __user *special, qid_t id, void __user *addr)
 308 {
 309         uint cmds, type;
 310         struct super_block *sb = NULL;
 311         struct block_device *bdev;
 312         char *tmp;
 313         int ret;
 314
 315         cmds = cmd >> SUBCMDSHIFT;
 316         type = cmd & SUBCMDMASK;
 317
 318         if (cmds != Q_SYNC || special) {
 319                 tmp = getname(special);
 320                 if (IS_ERR(tmp))
 321                         return PTR_ERR(tmp);
 322                 bdev = lookup_bdev(tmp);
 323                 putname(tmp);
 324                 if (IS_ERR(bdev))
 325                         return PTR_ERR(bdev);
 326                 sb = get_super(bdev);
 327                 bdput(bdev);
 328                 if (!sb)
 329                         return -ENODEV;
 330         }
 331
 332         ret = check_quotactl_valid(sb, type, cmds, id);
 333         if (ret >= 0)
 334                 ret = do_quotactl(sb, type, cmds, id, addr);
 335         if (sb)
 336                 drop_super(sb);
 337
 338         return ret;
 339 }