block/cmd-filter.c

   1 /*
   2  * Copyright 2004 Peter M. Jones <pjones@redhat.com>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License version 2 as
   6  * published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  *
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public Licens
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-
  17  *
  18  */
  19
  20 #include <linux/list.h>
  21 #include <linux/genhd.h>
  22 #include <linux/spinlock.h>
  23 #include <linux/capability.h>
  24 #include <linux/bitops.h>
  25
  26 #include <scsi/scsi.h>
  27 #include <linux/cdrom.h>
  28
  29 int blk_verify_command(struct blk_cmd_filter *filter,
  30                        unsigned char *cmd, int has_write_perm)
  31 {
  32         /* root can do any command. */
  33         if (capable(CAP_SYS_RAWIO))
  34                 return 0;
  35
  36         /* if there's no filter set, assume we're filtering everything out */
  37         if (!filter)
  38                 return -EPERM;
  39
  40         /* Anybody who can open the device can do a read-safe command */
  41         if (test_bit(cmd[0], filter->read_ok))
  42                 return 0;
  43
  44         /* Write-safe commands require a writable open */
  45         if (test_bit(cmd[0], filter->write_ok) && has_write_perm)
  46                 return 0;
  47
  48         return -EPERM;
  49 }
  50 EXPORT_SYMBOL(blk_verify_command);
  51
  52 #if 0
  53 /* and now, the sysfs stuff */
  54 static ssize_t rcf_cmds_show(struct blk_cmd_filter *filter, char *page,
  55                              int rw)
  56 {
  57         char *npage = page;
  58         unsigned long *okbits;
  59         int i;
  60
  61         if (rw == READ)
  62                 okbits = filter->read_ok;
  63         else
  64                 okbits = filter->write_ok;
  65
  66         for (i = 0; i < BLK_SCSI_MAX_CMDS; i++) {
  67                 if (test_bit(i, okbits)) {
  68                         npage += sprintf(npage, "0x%02x", i);
  69                         if (i < BLK_SCSI_MAX_CMDS - 1)
  70                                 sprintf(npage++, " ");
  71                 }
  72         }
  73
  74         if (npage != page)
  75                 npage += sprintf(npage, "\n");
  76
  77         return npage - page;
  78 }
  79
  80 static ssize_t rcf_readcmds_show(struct blk_cmd_filter *filter, char *page)
  81 {
  82         return rcf_cmds_show(filter, page, READ);
  83 }
  84
  85 static ssize_t rcf_writecmds_show(struct blk_cmd_filter *filter,
  86                                  char *page)
  87 {
  88         return rcf_cmds_show(filter, page, WRITE);
  89 }
  90
  91 static ssize_t rcf_cmds_store(struct blk_cmd_filter *filter,
  92                               const char *page, size_t count, int rw)
  93 {
  94         unsigned long okbits[BLK_SCSI_CMD_PER_LONG], *target_okbits;
  95         int cmd, set;
  96         char *p, *status;
  97
  98         if (rw == READ) {
  99                 memcpy(&okbits, filter->read_ok, sizeof(okbits));
 100                 target_okbits = filter->read_ok;
 101         } else {
 102                 memcpy(&okbits, filter->write_ok, sizeof(okbits));
 103                 target_okbits = filter->write_ok;
 104         }
 105
 106         while ((p = strsep((char **)&page, " ")) != NULL) {
 107                 set = 1;
 108
 109                 if (p[0] == '+') {
 110                         p++;
 111                 } else if (p[0] == '-') {
 112                         set = 0;
 113                         p++;
 114                 }
 115
 116                 cmd = simple_strtol(p, &status, 16);
 117
 118                 /* either of these cases means invalid input, so do nothing. */
 119                 if ((status == p) || cmd >= BLK_SCSI_MAX_CMDS)
 120                         return -EINVAL;
 121
 122                 if (set)
 123                         __set_bit(cmd, okbits);
 124                 else
 125                         __clear_bit(cmd, okbits);
 126         }
 127
 128         memcpy(target_okbits, okbits, sizeof(okbits));
 129         return count;
 130 }
 131
 132 static ssize_t rcf_readcmds_store(struct blk_cmd_filter *filter,
 133                                   const char *page, size_t count)
 134 {
 135         return rcf_cmds_store(filter, page, count, READ);
 136 }
 137
 138 static ssize_t rcf_writecmds_store(struct blk_cmd_filter *filter,
 139                                    const char *page, size_t count)
 140 {
 141         return rcf_cmds_store(filter, page, count, WRITE);
 142 }
 143
 144 struct rcf_sysfs_entry {
 145         struct attribute attr;
 146         ssize_t (*show)(struct blk_cmd_filter *, char *);
 147         ssize_t (*store)(struct blk_cmd_filter *, const char *, size_t);
 148 };
 149
 150 static struct rcf_sysfs_entry rcf_readcmds_entry = {
 151         .attr = { .name = "read_table", .mode = S_IRUGO | S_IWUSR },
 152         .show = rcf_readcmds_show,
 153         .store = rcf_readcmds_store,
 154 };
 155
 156 static struct rcf_sysfs_entry rcf_writecmds_entry = {
 157         .attr = {.name = "write_table", .mode = S_IRUGO | S_IWUSR },
 158         .show = rcf_writecmds_show,
 159         .store = rcf_writecmds_store,
 160 };
 161
 162 static struct attribute *default_attrs[] = {
 163         &rcf_readcmds_entry.attr,
 164         &rcf_writecmds_entry.attr,
 165         NULL,
 166 };
 167
 168 #define to_rcf(atr) container_of((atr), struct rcf_sysfs_entry, attr)
 169
 170 static ssize_t
 171 rcf_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
 172 {
 173         struct rcf_sysfs_entry *entry = to_rcf(attr);
 174         struct blk_cmd_filter *filter;
 175
 176         filter = container_of(kobj, struct blk_cmd_filter, kobj);
 177         if (entry->show)
 178                 return entry->show(filter, page);
 179
 180         return 0;
 181 }
 182
 183 static ssize_t
 184 rcf_attr_store(struct kobject *kobj, struct attribute *attr,
 185                         const char *page, size_t length)
 186 {
 187         struct rcf_sysfs_entry *entry = to_rcf(attr);
 188         struct blk_cmd_filter *filter;
 189
 190         if (!capable(CAP_SYS_RAWIO))
 191                 return -EPERM;
 192
 193         if (!entry->store)
 194                 return -EINVAL;
 195
 196         filter = container_of(kobj, struct blk_cmd_filter, kobj);
 197         return entry->store(filter, page, length);
 198 }
 199
 200 static struct sysfs_ops rcf_sysfs_ops = {
 201         .show = rcf_attr_show,
 202         .store = rcf_attr_store,
 203 };
 204
 205 static struct kobj_type rcf_ktype = {
 206         .sysfs_ops = &rcf_sysfs_ops,
 207         .default_attrs = default_attrs,
 208 };
 209
 210 int blk_register_filter(struct gendisk *disk)
 211 {
 212         int ret;
 213         struct blk_cmd_filter *filter = &disk->queue->cmd_filter;
 214         struct kobject *parent = kobject_get(disk->holder_dir->parent);
 215
 216         if (!parent)
 217                 return -ENODEV;
 218
 219         ret = kobject_init_and_add(&filter->kobj, &rcf_ktype, parent,
 220                                    "%s", "cmd_filter");
 221
 222         if (ret < 0)
 223                 return ret;
 224
 225         return 0;
 226 }
 227 EXPORT_SYMBOL(blk_register_filter);
 228
 229 void blk_unregister_filter(struct gendisk *disk)
 230 {
 231         struct blk_cmd_filter *filter = &disk->queue->cmd_filter;
 232
 233         kobject_put(&filter->kobj);
 234         kobject_put(disk->holder_dir->parent);
 235 }
 236 EXPORT_SYMBOL(blk_unregister_filter);
 237 #endif