aboutsummaryrefslogtreecommitdiff
path: root/block/cmd-filter.c
blob: 1d4026206ac2717b6f29826d3fcf014a68c0a127 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
/*
 * Copyright 2004 Peter M. Jones <pjones@redhat.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 *
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public Licens
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-
 *
 */

#include <linux/list.h>
#include <linux/genhd.h>
#include <linux/spinlock.h>
#include <linux/capability.h>
#include <linux/bitops.h>

#include <scsi/scsi.h>
#include <linux/cdrom.h>

int blk_verify_command(struct blk_cmd_filter *filter,
		       unsigned char *cmd, int has_write_perm)
{
	/* root can do any command. */
	if (capable(CAP_SYS_RAWIO))
		return 0;

	/* if there's no filter set, assume we're filtering everything out */
	if (!filter)
		return -EPERM;

	/* Anybody who can open the device can do a read-safe command */
	if (test_bit(cmd[0], filter->read_ok))
		return 0;

	/* Write-safe commands require a writable open */
	if (test_bit(cmd[0], filter->write_ok) && has_write_perm)
		return 0;

	return -EPERM;
}
EXPORT_SYMBOL(blk_verify_command);

/* and now, the sysfs stuff */
static ssize_t rcf_cmds_show(struct blk_cmd_filter *filter, char *page,
			     int rw)
{
	char *npage = page;
	unsigned long *okbits;
	int i;

	if (rw == READ)
		okbits = filter->read_ok;
	else
		okbits = filter->write_ok;

	for (i = 0; i < BLK_SCSI_MAX_CMDS; i++) {
		if (test_bit(i, okbits)) {
			npage += sprintf(npage, "0x%02x", i);
			if (i < BLK_SCSI_MAX_CMDS - 1)
				sprintf(npage++, " ");
		}
	}

	if (npage != page)
		npage += sprintf(npage, "\n");

	return npage - page;
}

static ssize_t rcf_readcmds_show(struct blk_cmd_filter *filter, char *page)
{
	return rcf_cmds_show(filter, page, READ);
}

static ssize_t rcf_writecmds_show(struct blk_cmd_filter *filter,
				 char *page)
{
	return rcf_cmds_show(filter, page, WRITE);
}

static ssize_t rcf_cmds_store(struct blk_cmd_filter *filter,
			      const char *page, size_t count, int rw)
{
	unsigned long okbits[BLK_SCSI_CMD_PER_LONG], *target_okbits;
	int cmd, set;
	char *p, *status;

	if (rw == READ) {
		memcpy(&okbits, filter->read_ok, sizeof(okbits));
		target_okbits = filter->read_ok;
	} else {
		memcpy(&okbits, filter->write_ok, sizeof(okbits));
		target_okbits = filter->write_ok;
	}

	while ((p = strsep((char **)&page, " ")) != NULL) {
		set = 1;

		if (p[0] == '+') {
			p++;
		} else if (p[0] == '-') {
			set = 0;
			p++;
		}

		cmd = simple_strtol(p, &status, 16);

		/* either of these cases means invalid input, so do nothing. */
		if ((status == p) || cmd >= BLK_SCSI_MAX_CMDS)
			return -EINVAL;

		if (set)
			__set_bit(cmd, okbits);
		else
			__clear_bit(cmd, okbits);
	}

	memcpy(target_okbits, okbits, sizeof(okbits));
	return count;
}

static ssize_t rcf_readcmds_store(struct blk_cmd_filter *filter,
				  const char *page, size_t count)
{
	return rcf_cmds_store(filter, page, count, READ);
}

static ssize_t rcf_writecmds_store(struct blk_cmd_filter *filter,
				   const char *page, size_t count)
{
	return rcf_cmds_store(filter, page, count, WRITE);
}

struct rcf_sysfs_entry {
	struct attribute attr;
	ssize_t (*show)(struct blk_cmd_filter *, char *);
	ssize_t (*store)(struct blk_cmd_filter *, const char *, size_t);
};

static struct rcf_sysfs_entry rcf_readcmds_entry = {
	.attr = { .name = "read_table", .mode = S_IRUGO | S_IWUSR },
	.show = rcf_readcmds_show,
	.store = rcf_readcmds_store,
};

static struct rcf_sysfs_entry rcf_writecmds_entry = {
	.attr = {.name = "write_table", .mode = S_IRUGO | S_IWUSR },
	.show = rcf_writecmds_show,
	.store = rcf_writecmds_store,
};

static struct attribute *default_attrs[] = {
	&rcf_readcmds_entry.attr,
	&rcf_writecmds_entry.attr,
	NULL,
};

#define to_rcf(atr) container_of((atr), struct rcf_sysfs_entry, attr)

static ssize_t
rcf_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
{
	struct rcf_sysfs_entry *entry = to_rcf(attr);
	struct blk_cmd_filter *filter;

	filter = container_of(kobj, struct blk_cmd_filter, kobj);
	if (entry->show)
		return entry->show(filter, page);

	return 0;
}

static ssize_t
rcf_attr_store(struct kobject *kobj, struct attribute *attr,
			const char *page, size_t length)
{
	struct rcf_sysfs_entry *entry = to_rcf(attr);
	struct blk_cmd_filter *filter;

	if (!capable(CAP_SYS_RAWIO))
		return -EPERM;

	if (!entry->store)
		return -EINVAL;

	filter = container_of(kobj, struct blk_cmd_filter, kobj);
	return entry->store(filter, page, length);
}

static struct sysfs_ops rcf_sysfs_ops = {
	.show = rcf_attr_show,
	.store = rcf_attr_store,
};

static struct kobj_type rcf_ktype = {
	.sysfs_ops = &rcf_sysfs_ops,
	.default_attrs = default_attrs,
};

int blk_register_filter(struct gendisk *disk)
{
	int ret;
	struct blk_cmd_filter *filter = &disk->queue->cmd_filter;
	struct kobject *parent = kobject_get(disk->holder_dir->parent);

	if (!parent)
		return -ENODEV;

	ret = kobject_init_and_add(&filter->kobj, &rcf_ktype, parent,
				   "%s", "cmd_filter");

	if (ret < 0)
		return ret;

	return 0;
}

void blk_unregister_filter(struct gendisk *disk)
{
	struct blk_cmd_filter *filter = &disk->queue->cmd_filter;

	kobject_put(&filter->kobj);
	kobject_put(disk->holder_dir->parent);
}