[mirror_ubuntu-artful-kernel.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 const 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;
	size_t 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;
	size_t 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->path.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 const 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;
03a44825	12	static const struct inode_operations proc_sys_inode_operations;
77b14db5 EB	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;
2a2da53b DH	174	ssize_t error;
2a2da53b DH	175	size_t res;
77b14db5 EB	176
	177	table = do_proc_sys_lookup(dentry->d_parent, &dentry->d_name, &head);
	178	/* Has the sysctl entry disappeared on us? */
	179	error = -ENOENT;
	180	if (!table)
	181	goto out;
	182
	183	/* Has the sysctl entry been replaced by a directory? */
	184	error = -EISDIR;
	185	if (!table->proc_handler)
	186	goto out;
	187
	188	/*
	189	* At this point we know that the sysctl was not unregistered
	190	* and won't be until we finish.
	191	*/
	192	error = -EPERM;
	193	if (sysctl_perm(table, MAY_READ))
	194	goto out;
	195
	196	/* careful: calling conventions are nasty here */
	197	res = count;
	198	error = table->proc_handler(table, 0, filp, buf, &res, ppos);
	199	if (!error)
	200	error = res;
	201	out:
	202	sysctl_head_finish(head);
	203
	204	return error;
	205	}
	206
	207	static ssize_t proc_sys_write(struct file filp, const char __user buf,
	208	size_t count, loff_t *ppos)
	209	{
	210	struct dentry *dentry = filp->f_dentry;
	211	struct ctl_table_header *head;
	212	struct ctl_table *table;
2a2da53b DH	213	ssize_t error;
2a2da53b DH	214	size_t res;
77b14db5 EB	215
	216	table = do_proc_sys_lookup(dentry->d_parent, &dentry->d_name, &head);
	217	/* Has the sysctl entry disappeared on us? */
	218	error = -ENOENT;
	219	if (!table)
	220	goto out;
	221
	222	/* Has the sysctl entry been replaced by a directory? */
	223	error = -EISDIR;
	224	if (!table->proc_handler)
	225	goto out;
	226
	227	/*
	228	* At this point we know that the sysctl was not unregistered
	229	* and won't be until we finish.
	230	*/
	231	error = -EPERM;
	232	if (sysctl_perm(table, MAY_WRITE))
	233	goto out;
	234
	235	/* careful: calling conventions are nasty here */
	236	res = count;
	237	error = table->proc_handler(table, 1, filp, (char __user *)buf,
	238	&res, ppos);
	239	if (!error)
	240	error = res;
	241	out:
	242	sysctl_head_finish(head);
	243
	244	return error;
	245	}
	246
	247
	248	static int proc_sys_fill_cache(struct file filp, void dirent,
	249	filldir_t filldir, struct ctl_table *table)
	250	{
	251	struct ctl_table_header *head;
	252	struct ctl_table *child_table = NULL;
	253	struct dentry child, dir = filp->f_path.dentry;
	254	struct inode *inode;
	255	struct qstr qname;
	256	ino_t ino = 0;
	257	unsigned type = DT_UNKNOWN;
	258	int ret;
	259
	260	qname.name = table->procname;
	261	qname.len = strlen(table->procname);
	262	qname.hash = full_name_hash(qname.name, qname.len);
	263
	264	/* Suppress duplicates.
	265	* Only fill a directory entry if it is the value that
	266	* an ordinary lookup of that name returns. Hide all
	267	* others.
	268	*
	269	* If we ever cache this translation in the dcache
	270	* I should do a dcache lookup first. But for now
	271	* it is just simpler not to.
	272	*/
	273	ret = 0;
	274	child_table = do_proc_sys_lookup(dir, &qname, &head);
	275	sysctl_head_finish(head);
	276	if (child_table != table)
	277	return 0;
	278
279	child = d_lookup(dir, &qname);
280	if (!child) {
281	struct dentry *new;
282	new = d_alloc(dir, &qname);
283	if (new) {
284	inode = proc_sys_make_inode(dir->d_inode, table);
285	if (!inode)
286	child = ERR_PTR(-ENOMEM);
287	else {
288	new->d_op = &proc_sys_dentry_operations;
289	d_add(new, inode);
290	}
291	if (child)
292	dput(new);
293	else
294	child = new;
295	}
296	}
297	if (!child \|\| IS_ERR(child) \|\| !child->d_inode)
298	goto end_instantiate;
299	inode = child->d_inode;
300	if (inode) {
301	ino = inode->i_ino;
302	type = inode->i_mode >> 12;
303	}
304	dput(child);
305	end_instantiate:
306	if (!ino)
307	ino= find_inode_number(dir, &qname);
308	if (!ino)
309	ino = 1;
310	return filldir(dirent, qname.name, qname.len, filp->f_pos, ino, type);
311	}
312
313	static int proc_sys_readdir(struct file filp, void dirent, filldir_t filldir)
314	{
315	struct dentry *dentry = filp->f_dentry;
316	struct inode *inode = dentry->d_inode;
317	struct ctl_table_header *head = NULL;
318	struct ctl_table *table;
319	unsigned long pos;
320	int ret;
321
322	ret = -ENOTDIR;
323	if (!S_ISDIR(inode->i_mode))
324	goto out;
325
326	ret = 0;
327	/* Avoid a switch here: arm builds fail with missing __cmpdi2 */
328	if (filp->f_pos == 0) {
329	if (filldir(dirent, ".", 1, filp->f_pos,
330	inode->i_ino, DT_DIR) < 0)
331	goto out;
332	filp->f_pos++;
333	}
334	if (filp->f_pos == 1) {
335	if (filldir(dirent, "..", 2, filp->f_pos,
336	parent_ino(dentry), DT_DIR) < 0)
337	goto out;
338	filp->f_pos++;
339	}
340	pos = 2;
341
342	/* - Find each instance of the directory
343	* - Read all entries in each instance
344	* - Before returning an entry to user space lookup the entry
345	* by name and if I find a different entry don't return
346	* this one because it means it is a buried dup.
347	* For sysctl this should only happen for directory entries.
348	*/
349	for (head = sysctl_head_next(NULL); head; head = sysctl_head_next(head)) {
350	table = proc_sys_lookup_table(dentry, head->ctl_table);
351
352	if (!table)
353	continue;
354
355	for (; table->ctl_name \|\| table->procname; table++, pos++) {
356	/* Can't do anything without a proc name */
357	if (!table->procname)
358	continue;
359
360	if (pos < filp->f_pos)
361	continue;
362
363	if (proc_sys_fill_cache(filp, dirent, filldir, table) < 0)
364	goto out;
365	filp->f_pos = pos + 1;
366	}
367	}
368	ret = 1;
369	out:
370	sysctl_head_finish(head);
371	return ret;
372	}
373
374	static int proc_sys_permission(struct inode inode, int mask, struct nameidata nd)
375	{
376	/*
377	* sysctl entries that are not writeable,
378	* are _NOT_ writeable, capabilities or not.
379	*/
380	struct ctl_table_header *head;
381	struct ctl_table *table;
382	struct dentry *dentry;
383	int mode;
384	int depth;
385	int error;
386
387	head = NULL;
388	depth = PROC_I(inode)->fd;
389
390	/* First check the cached permissions, in case we don't have
391	* enough information to lookup the sysctl table entry.
392	*/
393	error = -EACCES;
394	mode = inode->i_mode;
395
396	if (current->euid == 0)
397	mode >>= 6;
398	else if (in_group_p(0))
399	mode >>= 3;
400
401	if ((mode & mask & (MAY_READ\|MAY_WRITE\|MAY_EXEC)) == mask)
402	error = 0;
403
404	/* If we can't get a sysctl table entry the permission
405	* checks on the cached mode will have to be enough.
406	*/
407	if (!nd \|\| !depth)
408	goto out;
409
4ac91378	410	dentry = nd->path.dentry;
77b14db5 EB	411	table = do_proc_sys_lookup(dentry->d_parent, &dentry->d_name, &head);
	412
	413	/* If the entry does not exist deny permission */
	414	error = -EACCES;
	415	if (!table)
	416	goto out;
	417
	418	/* Use the permissions on the sysctl table entry */
	419	error = sysctl_perm(table, mask);
	420	out:
	421	sysctl_head_finish(head);
	422	return error;
	423	}
	424
	425	static int proc_sys_setattr(struct dentry dentry, struct iattr attr)
	426	{
	427	struct inode *inode = dentry->d_inode;
	428	int error;
	429
	430	if (attr->ia_valid & (ATTR_MODE \| ATTR_UID \| ATTR_GID))
	431	return -EPERM;
	432
	433	error = inode_change_ok(inode, attr);
9d0633cf JJ	434	if (!error)
9d0633cf JJ	435	error = inode_setattr(inode, attr);
77b14db5 EB	436
	437	return error;
	438	}
	439
	440	/* I'm lazy and don't distinguish between files and directories,
	441	* until access time.
	442	*/
	443	static const struct file_operations proc_sys_file_operations = {
	444	.read = proc_sys_read,
	445	.write = proc_sys_write,
	446	.readdir = proc_sys_readdir,
	447	};
	448
03a44825	449	static const struct inode_operations proc_sys_inode_operations = {
77b14db5 EB	450	.lookup = proc_sys_lookup,
	451	.permission = proc_sys_permission,
	452	.setattr = proc_sys_setattr,
	453	};
	454
	455	static int proc_sys_revalidate(struct dentry dentry, struct nameidata nd)
	456	{
	457	struct ctl_table_header *head;
	458	struct ctl_table *table;
	459	table = do_proc_sys_lookup(dentry->d_parent, &dentry->d_name, &head);
	460	proc_sys_refresh_inode(dentry->d_inode, table);
	461	sysctl_head_finish(head);
	462	return !!table;
	463	}
	464
	465	static struct dentry_operations proc_sys_dentry_operations = {
	466	.d_revalidate = proc_sys_revalidate,
	467	};
	468
	469	static struct proc_dir_entry *proc_sys_root;
	470
	471	int proc_sys_init(void)
	472	{
	473	proc_sys_root = proc_mkdir("sys", NULL);
	474	proc_sys_root->proc_iops = &proc_sys_inode_operations;
	475	proc_sys_root->proc_fops = &proc_sys_file_operations;
	476	proc_sys_root->nlink = 0;
	477	return 0;
	478	}