[linux.git] / fs / proc / proc_sysctl.c

/*
 * /proc/sys support
 */

#include <linux/sysctl.h>
#include <linux/proc_fs.h>
#include <linux/security.h>
#include "internal.h"

static struct dentry_operations proc_sys_dentry_operations;
static const struct file_operations proc_sys_file_operations;
static struct inode_operations proc_sys_inode_operations;

static void proc_sys_refresh_inode(struct inode *inode, struct ctl_table *table)
{
	/* Refresh the cached information bits in the inode */
	if (table) {
		inode->i_uid = 0;
		inode->i_gid = 0;
		inode->i_mode = table->mode;
		if (table->proc_handler) {
			inode->i_mode |= S_IFREG;
			inode->i_nlink = 1;
		} else {
			inode->i_mode |= S_IFDIR;
			inode->i_nlink = 0;	/* It is too hard to figure out */
		}
	}
}

static struct inode *proc_sys_make_inode(struct inode *dir, struct ctl_table *table)
{
	struct inode *inode;
	struct proc_inode *dir_ei, *ei;
	int depth;

	inode = new_inode(dir->i_sb);
	if (!inode)
		goto out;

	/* A directory is always one deeper than it's parent */
	dir_ei = PROC_I(dir);
	depth = dir_ei->fd + 1;

	ei = PROC_I(inode);
	ei->fd = depth;
	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
	inode->i_op = &proc_sys_inode_operations;
	inode->i_fop = &proc_sys_file_operations;
	inode->i_flags |= S_PRIVATE; /* tell selinux to ignore this inode */
	proc_sys_refresh_inode(inode, table);
out:
	return inode;
}

static struct dentry *proc_sys_ancestor(struct dentry *dentry, int depth)
{
	for (;;) {
		struct proc_inode *ei;

		ei = PROC_I(dentry->d_inode);
		if (ei->fd == depth)
			break; /* found */

		dentry = dentry->d_parent;
	}
	return dentry;
}

static struct ctl_table *proc_sys_lookup_table_one(struct ctl_table *table,
							struct qstr *name)
{
	int len;
	for ( ; table->ctl_name || table->procname; table++) {

		if (!table->procname)
			continue;

		len = strlen(table->procname);
		if (len != name->len)
			continue;

		if (memcmp(table->procname, name->name, len) != 0)
			continue;

		/* I have a match */
		return table;
	}
	return NULL;
}

static struct ctl_table *proc_sys_lookup_table(struct dentry *dentry,
						struct ctl_table *table)
{
	struct dentry *ancestor;
	struct proc_inode *ei;
	int depth, i;

	ei = PROC_I(dentry->d_inode);
	depth = ei->fd;

	if (depth == 0)
		return table;

	for (i = 1; table && (i <= depth); i++) {
		ancestor = proc_sys_ancestor(dentry, i);
		table = proc_sys_lookup_table_one(table, &ancestor->d_name);
		if (table)
			table = table->child;
	}
	return table;

}
static struct ctl_table *proc_sys_lookup_entry(struct dentry *dparent,
						struct qstr *name,
						struct ctl_table *table)
{
	table = proc_sys_lookup_table(dparent, table);
	if (table)
		table = proc_sys_lookup_table_one(table, name);
	return table;
}

static struct ctl_table *do_proc_sys_lookup(struct dentry *parent,
						struct qstr *name,
						struct ctl_table_header **ptr)
{
	struct ctl_table_header *head;
	struct ctl_table *table = NULL;

	for (head = sysctl_head_next(NULL); head;
			head = sysctl_head_next(head)) {
		table = proc_sys_lookup_entry(parent, name, head->ctl_table);
		if (table)
			break;
	}
	*ptr = head;
	return table;
}

static struct dentry *proc_sys_lookup(struct inode *dir, struct dentry *dentry,
					struct nameidata *nd)
{
	struct ctl_table_header *head;
	struct inode *inode;
	struct dentry *err;
	struct ctl_table *table;

	err = ERR_PTR(-ENOENT);
	table = do_proc_sys_lookup(dentry->d_parent, &dentry->d_name, &head);
	if (!table)
		goto out;

	err = ERR_PTR(-ENOMEM);
	inode = proc_sys_make_inode(dir, table);
	if (!inode)
		goto out;

	err = NULL;
	dentry->d_op = &proc_sys_dentry_operations;
	d_add(dentry, inode);

out:
	sysctl_head_finish(head);
	return err;
}

static ssize_t proc_sys_read(struct file *filp, char __user *buf,
				size_t count, loff_t *ppos)
{
	struct dentry *dentry = filp->f_dentry;
	struct ctl_table_header *head;
	struct ctl_table *table;
	ssize_t error, res;

	table = do_proc_sys_lookup(dentry->d_parent, &dentry->d_name, &head);
	/* Has the sysctl entry disappeared on us? */
	error = -ENOENT;
	if (!table)
		goto out;

	/* Has the sysctl entry been replaced by a directory? */
	error = -EISDIR;
	if (!table->proc_handler)
		goto out;

	/*
	 * At this point we know that the sysctl was not unregistered
	 * and won't be until we finish.
	 */
	error = -EPERM;
	if (sysctl_perm(table, MAY_READ))
		goto out;

	/* careful: calling conventions are nasty here */
	res = count;
	error = table->proc_handler(table, 0, filp, buf, &res, ppos);
	if (!error)
		error = res;
out:
	sysctl_head_finish(head);

	return error;
}

static ssize_t proc_sys_write(struct file *filp, const char __user *buf,
				size_t count, loff_t *ppos)
{
	struct dentry *dentry = filp->f_dentry;
	struct ctl_table_header *head;
	struct ctl_table *table;
	ssize_t error, res;

	table = do_proc_sys_lookup(dentry->d_parent, &dentry->d_name, &head);
	/* Has the sysctl entry disappeared on us? */
	error = -ENOENT;
	if (!table)
		goto out;

	/* Has the sysctl entry been replaced by a directory? */
	error = -EISDIR;
	if (!table->proc_handler)
		goto out;

	/*
	 * At this point we know that the sysctl was not unregistered
	 * and won't be until we finish.
	 */
	error = -EPERM;
	if (sysctl_perm(table, MAY_WRITE))
		goto out;

	/* careful: calling conventions are nasty here */
	res = count;
	error = table->proc_handler(table, 1, filp, (char __user *)buf,
				    &res, ppos);
	if (!error)
		error = res;
out:
	sysctl_head_finish(head);

	return error;
}


static int proc_sys_fill_cache(struct file *filp, void *dirent,
				filldir_t filldir, struct ctl_table *table)
{
	struct ctl_table_header *head;
	struct ctl_table *child_table = NULL;
	struct dentry *child, *dir = filp->f_path.dentry;
	struct inode *inode;
	struct qstr qname;
	ino_t ino = 0;
	unsigned type = DT_UNKNOWN;
	int ret;

	qname.name = table->procname;
	qname.len  = strlen(table->procname);
	qname.hash = full_name_hash(qname.name, qname.len);

	/* Suppress duplicates.
	 * Only fill a directory entry if it is the value that
	 * an ordinary lookup of that name returns.  Hide all
	 * others.
	 *
	 * If we ever cache this translation in the dcache
	 * I should do a dcache lookup first.  But for now
	 * it is just simpler not to.
	 */
	ret = 0;
	child_table = do_proc_sys_lookup(dir, &qname, &head);
	sysctl_head_finish(head);
	if (child_table != table)
		return 0;

	child = d_lookup(dir, &qname);
	if (!child) {
		struct dentry *new;
		new = d_alloc(dir, &qname);
		if (new) {
			inode = proc_sys_make_inode(dir->d_inode, table);
			if (!inode)
				child = ERR_PTR(-ENOMEM);
			else {
				new->d_op = &proc_sys_dentry_operations;
				d_add(new, inode);
			}
			if (child)
				dput(new);
			else
				child = new;
		}
	}
	if (!child || IS_ERR(child) || !child->d_inode)
		goto end_instantiate;
	inode = child->d_inode;
	if (inode) {
		ino  = inode->i_ino;
		type = inode->i_mode >> 12;
	}
	dput(child);
end_instantiate:
	if (!ino)
		ino= find_inode_number(dir, &qname);
	if (!ino)
		ino = 1;
	return filldir(dirent, qname.name, qname.len, filp->f_pos, ino, type);
}

static int proc_sys_readdir(struct file *filp, void *dirent, filldir_t filldir)
{
	struct dentry *dentry = filp->f_dentry;
	struct inode *inode = dentry->d_inode;
	struct ctl_table_header *head = NULL;
	struct ctl_table *table;
	unsigned long pos;
	int ret;

	ret = -ENOTDIR;
	if (!S_ISDIR(inode->i_mode))
		goto out;

	ret = 0;
	/* Avoid a switch here: arm builds fail with missing __cmpdi2 */
	if (filp->f_pos == 0) {
		if (filldir(dirent, ".", 1, filp->f_pos,
				inode->i_ino, DT_DIR) < 0)
			goto out;
		filp->f_pos++;
	}
	if (filp->f_pos == 1) {
		if (filldir(dirent, "..", 2, filp->f_pos,
				parent_ino(dentry), DT_DIR) < 0)
			goto out;
		filp->f_pos++;
	}
	pos = 2;

	/* - Find each instance of the directory
	 * - Read all entries in each instance
	 * - Before returning an entry to user space lookup the entry
	 *   by name and if I find a different entry don't return
	 *   this one because it means it is a buried dup.
	 * For sysctl this should only happen for directory entries.
	 */
	for (head = sysctl_head_next(NULL); head; head = sysctl_head_next(head)) {
		table = proc_sys_lookup_table(dentry, head->ctl_table);

		if (!table)
			continue;

		for (; table->ctl_name || table->procname; table++, pos++) {
			/* Can't do anything without a proc name */
			if (!table->procname)
				continue;

			if (pos < filp->f_pos)
				continue;

			if (proc_sys_fill_cache(filp, dirent, filldir, table) < 0)
				goto out;
			filp->f_pos = pos + 1;
		}
	}
	ret = 1;
out:
	sysctl_head_finish(head);
	return ret;
}

static int proc_sys_permission(struct inode *inode, int mask, struct nameidata *nd)
{
	/*
	 * sysctl entries that are not writeable,
	 * are _NOT_ writeable, capabilities or not.
	 */
	struct ctl_table_header *head;
	struct ctl_table *table;
	struct dentry *dentry;
	int mode;
	int depth;
	int error;

	head = NULL;
	depth = PROC_I(inode)->fd;

	/* First check the cached permissions, in case we don't have
	 * enough information to lookup the sysctl table entry.
	 */
	error = -EACCES;
	mode = inode->i_mode;

	if (current->euid == 0)
		mode >>= 6;
	else if (in_group_p(0))
		mode >>= 3;

	if ((mode & mask & (MAY_READ|MAY_WRITE|MAY_EXEC)) == mask)
		error = 0;

	/* If we can't get a sysctl table entry the permission
	 * checks on the cached mode will have to be enough.
	 */
	if (!nd || !depth)
		goto out;

	dentry = nd->dentry;
	table = do_proc_sys_lookup(dentry->d_parent, &dentry->d_name, &head);

	/* If the entry does not exist deny permission */
	error = -EACCES;
	if (!table)
		goto out;

	/* Use the permissions on the sysctl table entry */
	error = sysctl_perm(table, mask);
out:
	sysctl_head_finish(head);
	return error;
}

static int proc_sys_setattr(struct dentry *dentry, struct iattr *attr)
{
	struct inode *inode = dentry->d_inode;
	int error;

	if (attr->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))
		return -EPERM;

	error = inode_change_ok(inode, attr);
	if (!error)
		error = inode_setattr(inode, attr);

	return error;
}

/* I'm lazy and don't distinguish between files and directories,
 * until access time.
 */
static const struct file_operations proc_sys_file_operations = {
	.read		= proc_sys_read,
	.write		= proc_sys_write,
	.readdir	= proc_sys_readdir,
};

static struct inode_operations proc_sys_inode_operations = {
	.lookup		= proc_sys_lookup,
	.permission	= proc_sys_permission,
	.setattr	= proc_sys_setattr,
};

static int proc_sys_revalidate(struct dentry *dentry, struct nameidata *nd)
{
	struct ctl_table_header *head;
	struct ctl_table *table;
	table = do_proc_sys_lookup(dentry->d_parent, &dentry->d_name, &head);
	proc_sys_refresh_inode(dentry->d_inode, table);
	sysctl_head_finish(head);
	return !!table;
}

static struct dentry_operations proc_sys_dentry_operations = {
	.d_revalidate	= proc_sys_revalidate,
};

static struct proc_dir_entry *proc_sys_root;

int proc_sys_init(void)
{
	proc_sys_root = proc_mkdir("sys", NULL);
	proc_sys_root->proc_iops = &proc_sys_inode_operations;
	proc_sys_root->proc_fops = &proc_sys_file_operations;
	proc_sys_root->nlink = 0;
	return 0;
}
Commit	Line	Data
77b14db5 EB	1	/*
	2	* /proc/sys support
	3	*/
	4
	5	#include <linux/sysctl.h>
	6	#include <linux/proc_fs.h>
	7	#include <linux/security.h>
	8	#include "internal.h"
	9
	10	static struct dentry_operations proc_sys_dentry_operations;
	11	static const struct file_operations proc_sys_file_operations;
	12	static struct inode_operations proc_sys_inode_operations;
	13
	14	static void proc_sys_refresh_inode(struct inode inode, struct ctl_table table)
	15	{
	16	/* Refresh the cached information bits in the inode */
	17	if (table) {
	18	inode->i_uid = 0;
	19	inode->i_gid = 0;
	20	inode->i_mode = table->mode;
	21	if (table->proc_handler) {
	22	inode->i_mode \|= S_IFREG;
	23	inode->i_nlink = 1;
	24	} else {
	25	inode->i_mode \|= S_IFDIR;
	26	inode->i_nlink = 0; /* It is too hard to figure out */
	27	}
	28	}
	29	}
	30
	31	static struct inode proc_sys_make_inode(struct inode dir, struct ctl_table *table)
	32	{
	33	struct inode *inode;
	34	struct proc_inode dir_ei, ei;
	35	int depth;
	36
	37	inode = new_inode(dir->i_sb);
	38	if (!inode)
	39	goto out;
	40
	41	/* A directory is always one deeper than it's parent */
	42	dir_ei = PROC_I(dir);
	43	depth = dir_ei->fd + 1;
	44
	45	ei = PROC_I(inode);
	46	ei->fd = depth;
	47	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
	48	inode->i_op = &proc_sys_inode_operations;
	49	inode->i_fop = &proc_sys_file_operations;
86a71dbd	50	inode->i_flags \|= S_PRIVATE; /* tell selinux to ignore this inode */
77b14db5 EB	51	proc_sys_refresh_inode(inode, table);
	52	out:
	53	return inode;
	54	}
	55
	56	static struct dentry proc_sys_ancestor(struct dentry dentry, int depth)
	57	{
	58	for (;;) {
	59	struct proc_inode *ei;
	60
	61	ei = PROC_I(dentry->d_inode);
	62	if (ei->fd == depth)
	63	break; /* found */
	64
	65	dentry = dentry->d_parent;
	66	}
	67	return dentry;
	68	}
	69
	70	static struct ctl_table proc_sys_lookup_table_one(struct ctl_table table,
	71	struct qstr *name)
	72	{
	73	int len;
	74	for ( ; table->ctl_name \|\| table->procname; table++) {
	75
	76	if (!table->procname)
	77	continue;
	78
	79	len = strlen(table->procname);
	80	if (len != name->len)
	81	continue;
	82
	83	if (memcmp(table->procname, name->name, len) != 0)
	84	continue;
	85
	86	/* I have a match */
	87	return table;
	88	}
	89	return NULL;
	90	}
	91
	92	static struct ctl_table proc_sys_lookup_table(struct dentry dentry,
	93	struct ctl_table *table)
	94	{
	95	struct dentry *ancestor;
	96	struct proc_inode *ei;
	97	int depth, i;
	98
	99	ei = PROC_I(dentry->d_inode);
	100	depth = ei->fd;
	101
	102	if (depth == 0)
	103	return table;
	104
	105	for (i = 1; table && (i <= depth); i++) {
	106	ancestor = proc_sys_ancestor(dentry, i);
	107	table = proc_sys_lookup_table_one(table, &ancestor->d_name);
	108	if (table)
	109	table = table->child;
	110	}
	111	return table;
	112
	113	}
	114	static struct ctl_table proc_sys_lookup_entry(struct dentry dparent,
115	struct qstr *name,
116	struct ctl_table *table)
117	{
118	table = proc_sys_lookup_table(dparent, table);
119	if (table)
120	table = proc_sys_lookup_table_one(table, name);
121	return table;
122	}
123
124	static struct ctl_table do_proc_sys_lookup(struct dentry parent,
125	struct qstr *name,
126	struct ctl_table_header **ptr)
127	{
128	struct ctl_table_header *head;
129	struct ctl_table *table = NULL;
130
131	for (head = sysctl_head_next(NULL); head;
132	head = sysctl_head_next(head)) {
133	table = proc_sys_lookup_entry(parent, name, head->ctl_table);
134	if (table)
135	break;
136	}
137	*ptr = head;
138	return table;
139	}
140
141	static struct dentry proc_sys_lookup(struct inode dir, struct dentry *dentry,
142	struct nameidata *nd)
143	{
144	struct ctl_table_header *head;
145	struct inode *inode;
146	struct dentry *err;
147	struct ctl_table *table;
148
149	err = ERR_PTR(-ENOENT);
150	table = do_proc_sys_lookup(dentry->d_parent, &dentry->d_name, &head);
151	if (!table)
152	goto out;
153
154	err = ERR_PTR(-ENOMEM);
155	inode = proc_sys_make_inode(dir, table);
156	if (!inode)
157	goto out;
158
159	err = NULL;
160	dentry->d_op = &proc_sys_dentry_operations;
161	d_add(dentry, inode);
162
163	out:
164	sysctl_head_finish(head);
165	return err;
166	}
167
168	static ssize_t proc_sys_read(struct file filp, char __user buf,
169	size_t count, loff_t *ppos)
170	{
171	struct dentry *dentry = filp->f_dentry;
172	struct ctl_table_header *head;
173	struct ctl_table *table;
174	ssize_t error, res;
175
176	table = do_proc_sys_lookup(dentry->d_parent, &dentry->d_name, &head);
177	/* Has the sysctl entry disappeared on us? */
178	error = -ENOENT;
179	if (!table)
180	goto out;
181
182	/* Has the sysctl entry been replaced by a directory? */
183	error = -EISDIR;
184	if (!table->proc_handler)
185	goto out;
186
187	/*
188	* At this point we know that the sysctl was not unregistered
189	* and won't be until we finish.
190	*/
191	error = -EPERM;
192	if (sysctl_perm(table, MAY_READ))
193	goto out;
194
195	/* careful: calling conventions are nasty here */
196	res = count;
197	error = table->proc_handler(table, 0, filp, buf, &res, ppos);
198	if (!error)
199	error = res;
200	out:
201	sysctl_head_finish(head);
202
203	return error;
204	}
205
206	static ssize_t proc_sys_write(struct file filp, const char __user buf,
207	size_t count, loff_t *ppos)
208	{
209	struct dentry *dentry = filp->f_dentry;
210	struct ctl_table_header *head;
211	struct ctl_table *table;
212	ssize_t error, res;
213
214	table = do_proc_sys_lookup(dentry->d_parent, &dentry->d_name, &head);
215	/* Has the sysctl entry disappeared on us? */
216	error = -ENOENT;
217	if (!table)
218	goto out;
219
220	/* Has the sysctl entry been replaced by a directory? */
221	error = -EISDIR;
222	if (!table->proc_handler)
223	goto out;
224
225	/*
226	* At this point we know that the sysctl was not unregistered
227	* and won't be until we finish.
228	*/
229	error = -EPERM;
230	if (sysctl_perm(table, MAY_WRITE))
231	goto out;
232
233	/* careful: calling conventions are nasty here */
234	res = count;
235	error = table->proc_handler(table, 1, filp, (char __user *)buf,
236	&res, ppos);
237	if (!error)
238	error = res;
239	out:
240	sysctl_head_finish(head);
241
242	return error;
243	}
244
245
246	static int proc_sys_fill_cache(struct file filp, void dirent,
247	filldir_t filldir, struct ctl_table *table)
248	{
249	struct ctl_table_header *head;
250	struct ctl_table *child_table = NULL;
251	struct dentry child, dir = filp->f_path.dentry;
252	struct inode *inode;
253	struct qstr qname;
254	ino_t ino = 0;
255	unsigned type = DT_UNKNOWN;
256	int ret;
257
258	qname.name = table->procname;
259	qname.len = strlen(table->procname);
260	qname.hash = full_name_hash(qname.name, qname.len);
261
262	/* Suppress duplicates.
263	* Only fill a directory entry if it is the value that
264	* an ordinary lookup of that name returns. Hide all
265	* others.
266	*
267	* If we ever cache this translation in the dcache
268	* I should do a dcache lookup first. But for now
269	* it is just simpler not to.
270	*/
271	ret = 0;
272	child_table = do_proc_sys_lookup(dir, &qname, &head);
273	sysctl_head_finish(head);
274	if (child_table != table)
275	return 0;
276
277	child = d_lookup(dir, &qname);
278	if (!child) {
279	struct dentry *new;
280	new = d_alloc(dir, &qname);
281	if (new) {
282	inode = proc_sys_make_inode(dir->d_inode, table);
283	if (!inode)
284	child = ERR_PTR(-ENOMEM);
285	else {
286	new->d_op = &proc_sys_dentry_operations;
287	d_add(new, inode);
288	}
289	if (child)
290	dput(new);
291	else
292	child = new;
293	}
294	}
295	if (!child \|\| IS_ERR(child) \|\| !child->d_inode)
296	goto end_instantiate;
297	inode = child->d_inode;
298	if (inode) {
299	ino = inode->i_ino;
300	type = inode->i_mode >> 12;
301	}
302	dput(child);
303	end_instantiate:
304	if (!ino)
305	ino= find_inode_number(dir, &qname);
306	if (!ino)
307	ino = 1;
308	return filldir(dirent, qname.name, qname.len, filp->f_pos, ino, type);
309	}
310
311	static int proc_sys_readdir(struct file filp, void dirent, filldir_t filldir)
312	{
313	struct dentry *dentry = filp->f_dentry;
314	struct inode *inode = dentry->d_inode;
315	struct ctl_table_header *head = NULL;
316	struct ctl_table *table;
317	unsigned long pos;
318	int ret;
319
320	ret = -ENOTDIR;
321	if (!S_ISDIR(inode->i_mode))
322	goto out;
323
324	ret = 0;
325	/* Avoid a switch here: arm builds fail with missing __cmpdi2 */
326	if (filp->f_pos == 0) {
327	if (filldir(dirent, ".", 1, filp->f_pos,
328	inode->i_ino, DT_DIR) < 0)
329	goto out;
330	filp->f_pos++;
331	}
332	if (filp->f_pos == 1) {
333	if (filldir(dirent, "..", 2, filp->f_pos,
334	parent_ino(dentry), DT_DIR) < 0)
335	goto out;
336	filp->f_pos++;
337	}
338	pos = 2;
339
340	/* - Find each instance of the directory
341	* - Read all entries in each instance
342	* - Before returning an entry to user space lookup the entry
343	* by name and if I find a different entry don't return
344	* this one because it means it is a buried dup.
345	* For sysctl this should only happen for directory entries.
346	*/
347	for (head = sysctl_head_next(NULL); head; head = sysctl_head_next(head)) {
348	table = proc_sys_lookup_table(dentry, head->ctl_table);
349
350	if (!table)
351	continue;
352
353	for (; table->ctl_name \|\| table->procname; table++, pos++) {
354	/* Can't do anything without a proc name */
355	if (!table->procname)
356	continue;
357
358	if (pos < filp->f_pos)
359	continue;
360
361	if (proc_sys_fill_cache(filp, dirent, filldir, table) < 0)
362	goto out;
363	filp->f_pos = pos + 1;
364	}
365	}
366	ret = 1;
367	out:
368	sysctl_head_finish(head);
369	return ret;
370	}
371
372	static int proc_sys_permission(struct inode inode, int mask, struct nameidata nd)
373	{
374	/*
375	* sysctl entries that are not writeable,
376	* are _NOT_ writeable, capabilities or not.
377	*/
378	struct ctl_table_header *head;
379	struct ctl_table *table;
380	struct dentry *dentry;
381	int mode;
382	int depth;
383	int error;
384
385	head = NULL;
386	depth = PROC_I(inode)->fd;
387
388	/* First check the cached permissions, in case we don't have
389	* enough information to lookup the sysctl table entry.
390	*/
391	error = -EACCES;
392	mode = inode->i_mode;
393
394	if (current->euid == 0)
395	mode >>= 6;
396	else if (in_group_p(0))
397	mode >>= 3;
398
399	if ((mode & mask & (MAY_READ\|MAY_WRITE\|MAY_EXEC)) == mask)
400	error = 0;
401
402	/* If we can't get a sysctl table entry the permission
403	* checks on the cached mode will have to be enough.
404	*/
405	if (!nd \|\| !depth)
406	goto out;
407
408	dentry = nd->dentry;
409	table = do_proc_sys_lookup(dentry->d_parent, &dentry->d_name, &head);
410
411	/* If the entry does not exist deny permission */
412	error = -EACCES;
413	if (!table)
414	goto out;
415
416	/* Use the permissions on the sysctl table entry */
417	error = sysctl_perm(table, mask);
418	out:
419	sysctl_head_finish(head);
420	return error;
421	}
422
423	static int proc_sys_setattr(struct dentry dentry, struct iattr attr)
424	{
425	struct inode *inode = dentry->d_inode;
426	int error;
427
428	if (attr->ia_valid & (ATTR_MODE \| ATTR_UID \| ATTR_GID))
429	return -EPERM;
430
431	error = inode_change_ok(inode, attr);
9d0633cf JJ	432	if (!error)
9d0633cf JJ	433	error = inode_setattr(inode, attr);
77b14db5 EB	434
	435	return error;
	436	}
	437
	438	/* I'm lazy and don't distinguish between files and directories,
	439	* until access time.
	440	*/
	441	static const struct file_operations proc_sys_file_operations = {
	442	.read = proc_sys_read,
	443	.write = proc_sys_write,
	444	.readdir = proc_sys_readdir,
	445	};
	446
	447	static struct inode_operations proc_sys_inode_operations = {
	448	.lookup = proc_sys_lookup,
	449	.permission = proc_sys_permission,
	450	.setattr = proc_sys_setattr,
	451	};
	452
	453	static int proc_sys_revalidate(struct dentry dentry, struct nameidata nd)
	454	{
	455	struct ctl_table_header *head;
	456	struct ctl_table *table;
	457	table = do_proc_sys_lookup(dentry->d_parent, &dentry->d_name, &head);
	458	proc_sys_refresh_inode(dentry->d_inode, table);
	459	sysctl_head_finish(head);
	460	return !!table;
	461	}
	462
	463	static struct dentry_operations proc_sys_dentry_operations = {
	464	.d_revalidate = proc_sys_revalidate,
	465	};
	466
	467	static struct proc_dir_entry *proc_sys_root;
	468
	469	int proc_sys_init(void)
	470	{
	471	proc_sys_root = proc_mkdir("sys", NULL);
	472	proc_sys_root->proc_iops = &proc_sys_inode_operations;
	473	proc_sys_root->proc_fops = &proc_sys_file_operations;
	474	proc_sys_root->nlink = 0;
	475	return 0;
	476	}