linux/block/cmd-filter.c
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   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
  29int blk_verify_command(struct blk_cmd_filter *filter,
  30                       unsigned char *cmd, fmode_t 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}
  50EXPORT_SYMBOL(blk_verify_command);
  51
  52#if 0
  53/* and now, the sysfs stuff */
  54static 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
  80static ssize_t rcf_readcmds_show(struct blk_cmd_filter *filter, char *page)
  81{
  82        return rcf_cmds_show(filter, page, READ);
  83}
  84
  85static ssize_t rcf_writecmds_show(struct blk_cmd_filter *filter,
  86                                 char *page)
  87{
  88        return rcf_cmds_show(filter, page, WRITE);
  89}
  90
  91static 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
 132static 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
 138static 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
 144struct 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
 150static 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
 156static 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
 162static 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
 170static ssize_t
 171rcf_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
 183static ssize_t
 184rcf_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
 200static struct sysfs_ops rcf_sysfs_ops = {
 201        .show = rcf_attr_show,
 202        .store = rcf_attr_store,
 203};
 204
 205static struct kobj_type rcf_ktype = {
 206        .sysfs_ops = &rcf_sysfs_ops,
 207        .default_attrs = default_attrs,
 208};
 209
 210int blk_register_filter(struct gendisk *disk)
 211{
 212        int ret;
 213        struct blk_cmd_filter *filter = &disk->queue->cmd_filter;
 214
 215        ret = kobject_init_and_add(&filter->kobj, &rcf_ktype,
 216                                   &disk_to_dev(disk)->kobj,
 217                                   "%s", "cmd_filter");
 218        if (ret < 0)
 219                return ret;
 220
 221        return 0;
 222}
 223EXPORT_SYMBOL(blk_register_filter);
 224
 225void blk_unregister_filter(struct gendisk *disk)
 226{
 227        struct blk_cmd_filter *filter = &disk->queue->cmd_filter;
 228
 229        kobject_put(&filter->kobj);
 230}
 231EXPORT_SYMBOL(blk_unregister_filter);
 232#endif
 233
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