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 #include <linux/blkdev.h>
  26
  27 #include <scsi/scsi.h>
  28 #include <linux/cdrom.h>
  29
  30 int blk_verify_command(struct blk_cmd_filter *filter,
  31                        unsigned char *cmd, fmode_t has_write_perm)
  32 {
  33         /* root can do any command. */
  34         if (capable(CAP_SYS_RAWIO))
  35                 return 0;
  36
  37         /* if there's no filter set, assume we're filtering everything out */
  38         if (!filter)
  39                 return -EPERM;
  40
  41         /* Anybody who can open the device can do a read-safe command */
  42         if (test_bit(cmd[0], filter->read_ok))
  43                 return 0;
  44
  45         /* Write-safe commands require a writable open */
  46         if (test_bit(cmd[0], filter->write_ok) && has_write_perm)
  47                 return 0;
  48
  49         return -EPERM;
  50 }
  51 EXPORT_SYMBOL(blk_verify_command);
  52
  53 #if 0
  54 /* and now, the sysfs stuff */
  55 static ssize_t rcf_cmds_show(struct blk_cmd_filter *filter, char *page,
  56                              int rw)
  57 {
  58         char *npage = page;
  59         unsigned long *okbits;
  60         int i;
  61
  62         if (rw == READ)
  63                 okbits = filter->read_ok;
  64         else
  65                 okbits = filter->write_ok;
  66
  67         for (i = 0; i < BLK_SCSI_MAX_CMDS; i++) {
  68                 if (test_bit(i, okbits)) {
  69                         npage += sprintf(npage, "0x%02x", i);
  70                         if (i < BLK_SCSI_MAX_CMDS - 1)
  71                                 sprintf(npage++, " ");
  72                 }
  73         }
  74
  75         if (npage != page)
  76                 npage += sprintf(npage, "\n");
  77
  78         return npage - page;
  79 }
  80
  81 static ssize_t rcf_readcmds_show(struct blk_cmd_filter *filter, char *page)
  82 {
  83         return rcf_cmds_show(filter, page, READ);
  84 }
  85
  86 static ssize_t rcf_writecmds_show(struct blk_cmd_filter *filter,
  87                                  char *page)
  88 {
  89         return rcf_cmds_show(filter, page, WRITE);
  90 }
  91
  92 static ssize_t rcf_cmds_store(struct blk_cmd_filter *filter,
  93                               const char *page, size_t count, int rw)
  94 {
  95         unsigned long okbits[BLK_SCSI_CMD_PER_LONG], *target_okbits;
  96         int cmd, set;
  97         char *p, *status;
  98
  99         if (rw == READ) {
 100                 memcpy(&okbits, filter->read_ok, sizeof(okbits));
 101                 target_okbits = filter->read_ok;
 102         } else {
 103                 memcpy(&okbits, filter->write_ok, sizeof(okbits));
 104                 target_okbits = filter->write_ok;
 105         }
 106
 107         while ((p = strsep((char **)&page, " ")) != NULL) {
 108                 set = 1;
 109
 110                 if (p[0] == '+') {
 111                         p++;
 112                 } else if (p[0] == '-') {
 113                         set = 0;
 114                         p++;
 115                 }
 116
 117                 cmd = simple_strtol(p, &status, 16);
 118
 119                 /* either of these cases means invalid input, so do nothing. */
 120                 if ((status == p) || cmd >= BLK_SCSI_MAX_CMDS)
 121                         return -EINVAL;
 122
 123                 if (set)
 124                         __set_bit(cmd, okbits);
 125                 else
 126                         __clear_bit(cmd, okbits);
 127         }
 128
 129         memcpy(target_okbits, okbits, sizeof(okbits));
 130         return count;
 131 }
 132
 133 static ssize_t rcf_readcmds_store(struct blk_cmd_filter *filter,
 134                                   const char *page, size_t count)
 135 {
 136         return rcf_cmds_store(filter, page, count, READ);
 137 }
 138
 139 static ssize_t rcf_writecmds_store(struct blk_cmd_filter *filter,
 140                                    const char *page, size_t count)
 141 {
 142         return rcf_cmds_store(filter, page, count, WRITE);
 143 }
 144
 145 struct rcf_sysfs_entry {
 146         struct attribute attr;
 147         ssize_t (*show)(struct blk_cmd_filter *, char *);
 148         ssize_t (*store)(struct blk_cmd_filter *, const char *, size_t);
 149 };
 150
 151 static struct rcf_sysfs_entry rcf_readcmds_entry = {
 152         .attr = { .name = "read_table", .mode = S_IRUGO | S_IWUSR },
 153         .show = rcf_readcmds_show,
 154         .store = rcf_readcmds_store,
 155 };
 156
 157 static struct rcf_sysfs_entry rcf_writecmds_entry = {
 158         .attr = {.name = "write_table", .mode = S_IRUGO | S_IWUSR },
 159         .show = rcf_writecmds_show,
 160         .store = rcf_writecmds_store,
 161 };
 162
 163 static struct attribute *default_attrs[] = {
 164         &rcf_readcmds_entry.attr,
 165         &rcf_writecmds_entry.attr,
 166         NULL,
 167 };
 168
 169 #define to_rcf(atr) container_of((atr), struct rcf_sysfs_entry, attr)
 170
 171 static ssize_t
 172 rcf_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
 173 {
 174         struct rcf_sysfs_entry *entry = to_rcf(attr);
 175         struct blk_cmd_filter *filter;
 176
 177         filter = container_of(kobj, struct blk_cmd_filter, kobj);
 178         if (entry->show)
 179                 return entry->show(filter, page);
 180
 181         return 0;
 182 }
 183
 184 static ssize_t
 185 rcf_attr_store(struct kobject *kobj, struct attribute *attr,
 186                         const char *page, size_t length)
 187 {
 188         struct rcf_sysfs_entry *entry = to_rcf(attr);
 189         struct blk_cmd_filter *filter;
 190
 191         if (!capable(CAP_SYS_RAWIO))
 192                 return -EPERM;
 193
 194         if (!entry->store)
 195                 return -EINVAL;
 196
 197         filter = container_of(kobj, struct blk_cmd_filter, kobj);
 198         return entry->store(filter, page, length);
 199 }
 200
 201 static struct sysfs_ops rcf_sysfs_ops = {
 202         .show = rcf_attr_show,
 203         .store = rcf_attr_store,
 204 };
 205
 206 static struct kobj_type rcf_ktype = {
 207         .sysfs_ops = &rcf_sysfs_ops,
 208         .default_attrs = default_attrs,
 209 };
 210
 211 int blk_register_filter(struct gendisk *disk)
 212 {
 213         int ret;
 214         struct blk_cmd_filter *filter = &disk->queue->cmd_filter;
 215
 216         ret = kobject_init_and_add(&filter->kobj, &rcf_ktype,
 217                                    &disk_to_dev(disk)->kobj,
 218                                    "%s", "cmd_filter");
 219         if (ret < 0)
 220                 return ret;
 221
 222         return 0;
 223 }
 224 EXPORT_SYMBOL(blk_register_filter);
 225
 226 void blk_unregister_filter(struct gendisk *disk)
 227 {
 228         struct blk_cmd_filter *filter = &disk->queue->cmd_filter;
 229
 230         kobject_put(&filter->kobj);
 231 }
 232 EXPORT_SYMBOL(blk_unregister_filter);
 233 #endif