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 /* and now, the sysfs stuff */
  53 static ssize_t rcf_cmds_show(struct blk_cmd_filter *filter, char *page,
  54                              int rw)
  55 {
  56         char *npage = page;
  57         unsigned long *okbits;
  58         int i;
  59
  60         if (rw == READ)
  61                 okbits = filter->read_ok;
  62         else
  63                 okbits = filter->write_ok;
  64
  65         for (i = 0; i < BLK_SCSI_MAX_CMDS; i++) {
  66                 if (test_bit(i, okbits)) {
  67                         npage += sprintf(npage, "0x%02x", i);
  68                         if (i < BLK_SCSI_MAX_CMDS - 1)
  69                                 sprintf(npage++, " ");
  70                 }
  71         }
  72
  73         if (npage != page)
  74                 npage += sprintf(npage, "\n");
  75
  76         return npage - page;
  77 }
  78
  79 static ssize_t rcf_readcmds_show(struct blk_cmd_filter *filter, char *page)
  80 {
  81         return rcf_cmds_show(filter, page, READ);
  82 }
  83
  84 static ssize_t rcf_writecmds_show(struct blk_cmd_filter *filter,
  85                                  char *page)
  86 {
  87         return rcf_cmds_show(filter, page, WRITE);
  88 }
  89
  90 static ssize_t rcf_cmds_store(struct blk_cmd_filter *filter,
  91                               const char *page, size_t count, int rw)
  92 {
  93         unsigned long okbits[BLK_SCSI_CMD_PER_LONG], *target_okbits;
  94         int cmd, set;
  95         char *p, *status;
  96
  97         if (rw == READ) {
  98                 memcpy(&okbits, filter->read_ok, sizeof(okbits));
  99                 target_okbits = filter->read_ok;
 100         } else {
 101                 memcpy(&okbits, filter->write_ok, sizeof(okbits));
 102                 target_okbits = filter->write_ok;
 103         }
 104
 105         while ((p = strsep((char **)&page, " ")) != NULL) {
 106                 set = 1;
 107
 108                 if (p[0] == '+') {
 109                         p++;
 110                 } else if (p[0] == '-') {
 111                         set = 0;
 112                         p++;
 113                 }
 114
 115                 cmd = simple_strtol(p, &status, 16);
 116
 117                 /* either of these cases means invalid input, so do nothing. */
 118                 if ((status == p) || cmd >= BLK_SCSI_MAX_CMDS)
 119                         return -EINVAL;
 120
 121                 if (set)
 122                         __set_bit(cmd, okbits);
 123                 else
 124                         __clear_bit(cmd, okbits);
 125         }
 126
 127         memcpy(target_okbits, okbits, sizeof(okbits));
 128         return count;
 129 }
 130
 131 static ssize_t rcf_readcmds_store(struct blk_cmd_filter *filter,
 132                                   const char *page, size_t count)
 133 {
 134         return rcf_cmds_store(filter, page, count, READ);
 135 }
 136
 137 static ssize_t rcf_writecmds_store(struct blk_cmd_filter *filter,
 138                                    const char *page, size_t count)
 139 {
 140         return rcf_cmds_store(filter, page, count, WRITE);
 141 }
 142
 143 struct rcf_sysfs_entry {
 144         struct attribute attr;
 145         ssize_t (*show)(struct blk_cmd_filter *, char *);
 146         ssize_t (*store)(struct blk_cmd_filter *, const char *, size_t);
 147 };
 148
 149 static struct rcf_sysfs_entry rcf_readcmds_entry = {
 150         .attr = { .name = "read_table", .mode = S_IRUGO | S_IWUSR },
 151         .show = rcf_readcmds_show,
 152         .store = rcf_readcmds_store,
 153 };
 154
 155 static struct rcf_sysfs_entry rcf_writecmds_entry = {
 156         .attr = {.name = "write_table", .mode = S_IRUGO | S_IWUSR },
 157         .show = rcf_writecmds_show,
 158         .store = rcf_writecmds_store,
 159 };
 160
 161 static struct attribute *default_attrs[] = {
 162         &rcf_readcmds_entry.attr,
 163         &rcf_writecmds_entry.attr,
 164         NULL,
 165 };
 166
 167 #define to_rcf(atr) container_of((atr), struct rcf_sysfs_entry, attr)
 168
 169 static ssize_t
 170 rcf_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
 171 {
 172         struct rcf_sysfs_entry *entry = to_rcf(attr);
 173         struct blk_cmd_filter *filter;
 174
 175         filter = container_of(kobj, struct blk_cmd_filter, kobj);
 176         if (entry->show)
 177                 return entry->show(filter, page);
 178
 179         return 0;
 180 }
 181
 182 static ssize_t
 183 rcf_attr_store(struct kobject *kobj, struct attribute *attr,
 184                         const char *page, size_t length)
 185 {
 186         struct rcf_sysfs_entry *entry = to_rcf(attr);
 187         struct blk_cmd_filter *filter;
 188
 189         if (!capable(CAP_SYS_RAWIO))
 190                 return -EPERM;
 191
 192         if (!entry->store)
 193                 return -EINVAL;
 194
 195         filter = container_of(kobj, struct blk_cmd_filter, kobj);
 196         return entry->store(filter, page, length);
 197 }
 198
 199 static struct sysfs_ops rcf_sysfs_ops = {
 200         .show = rcf_attr_show,
 201         .store = rcf_attr_store,
 202 };
 203
 204 static struct kobj_type rcf_ktype = {
 205         .sysfs_ops = &rcf_sysfs_ops,
 206         .default_attrs = default_attrs,
 207 };
 208
 209 int blk_register_filter(struct gendisk *disk)
 210 {
 211         int ret;
 212         struct blk_cmd_filter *filter = &disk->queue->cmd_filter;
 213         struct kobject *parent = kobject_get(disk->holder_dir->parent);
 214
 215         if (!parent)
 216                 return -ENODEV;
 217
 218         ret = kobject_init_and_add(&filter->kobj, &rcf_ktype, parent,
 219                                    "%s", "cmd_filter");
 220
 221         if (ret < 0)
 222                 return ret;
 223
 224         return 0;
 225 }
 226
 227 void blk_unregister_filter(struct gendisk *disk)
 228 {
 229         struct blk_cmd_filter *filter = &disk->queue->cmd_filter;
 230
 231         kobject_put(&filter->kobj);
 232         kobject_put(disk->holder_dir->parent);
 233 }
 234