Commit 1f87f0b5 authored by Eric W. Biederman's avatar Eric W. Biederman
Browse files

sysctl: Move the implementation into fs/proc/proc_sysctl.c 



Move the core sysctl code from kernel/sysctl.c and kernel/sysctl_check.c
into fs/proc/proc_sysctl.c.

Currently sysctl maintenance is hampered by the sysctl implementation
being split across 3 files with artificial layering between them.
Consolidate the entire sysctl implementation into 1 file so that
it is easier to see what is going on and hopefully allowing for
simpler maintenance.

For functions that are now only used in fs/proc/proc_sysctl.c remove
their declarations from sysctl.h and make them static in fs/proc/proc_sysctl.c

Signed-off-by: default avatarEric W. Biederman <ebiederm@xmission.com>
parent de4e83bd

fs/proc/internal.h

+3 −0
Original line number Diff line number Diff line
@@ -10,12 +10,15 @@ 
 */



#include <linux/proc_fs.h>

struct  ctl_table_header;



extern struct proc_dir_entry proc_root;

#ifdef CONFIG_PROC_SYSCTL

extern int proc_sys_init(void);

extern void sysctl_head_put(struct ctl_table_header *head);

#else

static inline void proc_sys_init(void) { }

static inline void sysctl_head_put(struct ctl_table_header *head) { }

#endif

#ifdef CONFIG_NET

extern int proc_net_init(void);

fs/proc/proc_sysctl.c

+622 −0
Original line number Diff line number Diff line
@@ -7,6 +7,7 @@ 
#include <linux/proc_fs.h>

#include <linux/security.h>

#include <linux/namei.h>

#include <linux/module.h>

#include "internal.h"



static const struct dentry_operations proc_sys_dentry_operations;
@@ -24,6 +25,209 @@ void proc_sys_poll_notify(struct ctl_table_poll *poll) 
	wake_up_interruptible(&poll->wait);

}



static struct ctl_table root_table[1];

static struct ctl_table_root sysctl_table_root;

static struct ctl_table_header root_table_header = {

	{{.count = 1,

	.ctl_table = root_table,

	.ctl_entry = LIST_HEAD_INIT(sysctl_table_root.default_set.list),}},

	.root = &sysctl_table_root,

	.set = &sysctl_table_root.default_set,

};

static struct ctl_table_root sysctl_table_root = {

	.root_list = LIST_HEAD_INIT(sysctl_table_root.root_list),

	.default_set.list = LIST_HEAD_INIT(root_table_header.ctl_entry),

};



static DEFINE_SPINLOCK(sysctl_lock);



/* called under sysctl_lock */

static int use_table(struct ctl_table_header *p)

{

	if (unlikely(p->unregistering))

		return 0;

	p->used++;

	return 1;

}



/* called under sysctl_lock */

static void unuse_table(struct ctl_table_header *p)

{

	if (!--p->used)

		if (unlikely(p->unregistering))

			complete(p->unregistering);

}



/* called under sysctl_lock, will reacquire if has to wait */

static void start_unregistering(struct ctl_table_header *p)

{

	/*

	 * if p->used is 0, nobody will ever touch that entry again;

	 * we'll eliminate all paths to it before dropping sysctl_lock

	 */

	if (unlikely(p->used)) {

		struct completion wait;

		init_completion(&wait);

		p->unregistering = &wait;

		spin_unlock(&sysctl_lock);

		wait_for_completion(&wait);

		spin_lock(&sysctl_lock);

	} else {

		/* anything non-NULL; we'll never dereference it */

		p->unregistering = ERR_PTR(-EINVAL);

	}

	/*

	 * do not remove from the list until nobody holds it; walking the

	 * list in do_sysctl() relies on that.

	 */

	list_del_init(&p->ctl_entry);

}



static void sysctl_head_get(struct ctl_table_header *head)

{

	spin_lock(&sysctl_lock);

	head->count++;

	spin_unlock(&sysctl_lock);

}



void sysctl_head_put(struct ctl_table_header *head)

{

	spin_lock(&sysctl_lock);

	if (!--head->count)

		kfree_rcu(head, rcu);

	spin_unlock(&sysctl_lock);

}



static struct ctl_table_header *sysctl_head_grab(struct ctl_table_header *head)

{

	if (!head)

		BUG();

	spin_lock(&sysctl_lock);

	if (!use_table(head))

		head = ERR_PTR(-ENOENT);

	spin_unlock(&sysctl_lock);

	return head;

}



static void sysctl_head_finish(struct ctl_table_header *head)

{

	if (!head)

		return;

	spin_lock(&sysctl_lock);

	unuse_table(head);

	spin_unlock(&sysctl_lock);

}



static struct ctl_table_set *

lookup_header_set(struct ctl_table_root *root, struct nsproxy *namespaces)

{

	struct ctl_table_set *set = &root->default_set;

	if (root->lookup)

		set = root->lookup(root, namespaces);

	return set;

}



static struct list_head *

lookup_header_list(struct ctl_table_root *root, struct nsproxy *namespaces)

{

	struct ctl_table_set *set = lookup_header_set(root, namespaces);

	return &set->list;

}



static struct ctl_table_header *__sysctl_head_next(struct nsproxy *namespaces,

						struct ctl_table_header *prev)

{

	struct ctl_table_root *root;

	struct list_head *header_list;

	struct ctl_table_header *head;

	struct list_head *tmp;



	spin_lock(&sysctl_lock);

	if (prev) {

		head = prev;

		tmp = &prev->ctl_entry;

		unuse_table(prev);

		goto next;

	}

	tmp = &root_table_header.ctl_entry;

	for (;;) {

		head = list_entry(tmp, struct ctl_table_header, ctl_entry);



		if (!use_table(head))

			goto next;

		spin_unlock(&sysctl_lock);

		return head;

	next:

		root = head->root;

		tmp = tmp->next;

		header_list = lookup_header_list(root, namespaces);

		if (tmp != header_list)

			continue;



		do {

			root = list_entry(root->root_list.next,

					struct ctl_table_root, root_list);

			if (root == &sysctl_table_root)

				goto out;

			header_list = lookup_header_list(root, namespaces);

		} while (list_empty(header_list));

		tmp = header_list->next;

	}

out:

	spin_unlock(&sysctl_lock);

	return NULL;

}



static struct ctl_table_header *sysctl_head_next(struct ctl_table_header *prev)

{

	return __sysctl_head_next(current->nsproxy, prev);

}



void register_sysctl_root(struct ctl_table_root *root)

{

	spin_lock(&sysctl_lock);

	list_add_tail(&root->root_list, &sysctl_table_root.root_list);

	spin_unlock(&sysctl_lock);

}



/*

 * sysctl_perm does NOT grant the superuser all rights automatically, because

 * some sysctl variables are readonly even to root.

 */



static int test_perm(int mode, int op)

{

	if (!current_euid())

		mode >>= 6;

	else if (in_egroup_p(0))

		mode >>= 3;

	if ((op & ~mode & (MAY_READ|MAY_WRITE|MAY_EXEC)) == 0)

		return 0;

	return -EACCES;

}



static int sysctl_perm(struct ctl_table_root *root, struct ctl_table *table, int op)

{

	int mode;



	if (root->permissions)

		mode = root->permissions(root, current->nsproxy, table);

	else

		mode = table->mode;



	return test_perm(mode, op);

}



static void sysctl_set_parent(struct ctl_table *parent, struct ctl_table *table)

{

	for (; table->procname; table++) {

		table->parent = parent;

		if (table->child)

			sysctl_set_parent(table, table->child);

	}

}





static struct inode *proc_sys_make_inode(struct super_block *sb,

		struct ctl_table_header *head, struct ctl_table *table)

{
@@ -435,6 +639,21 @@ static int proc_sys_delete(const struct dentry *dentry) 
	return !!PROC_I(dentry->d_inode)->sysctl->unregistering;

}



static int sysctl_is_seen(struct ctl_table_header *p)

{

	struct ctl_table_set *set = p->set;

	int res;

	spin_lock(&sysctl_lock);

	if (p->unregistering)

		res = 0;

	else if (!set->is_seen)

		res = 1;

	else

		res = set->is_seen(set);

	spin_unlock(&sysctl_lock);

	return res;

}



static int proc_sys_compare(const struct dentry *parent,

		const struct inode *pinode,

		const struct dentry *dentry, const struct inode *inode,
@@ -460,6 +679,409 @@ static const struct dentry_operations proc_sys_dentry_operations = { 
	.d_compare	= proc_sys_compare,

};



static struct ctl_table *is_branch_in(struct ctl_table *branch,

				      struct ctl_table *table)

{

	struct ctl_table *p;

	const char *s = branch->procname;



	/* branch should have named subdirectory as its first element */

	if (!s || !branch->child)

		return NULL;



	/* ... and nothing else */

	if (branch[1].procname)

		return NULL;



	/* table should contain subdirectory with the same name */

	for (p = table; p->procname; p++) {

		if (!p->child)

			continue;

		if (p->procname && strcmp(p->procname, s) == 0)

			return p;

	}

	return NULL;

}



/* see if attaching q to p would be an improvement */

static void try_attach(struct ctl_table_header *p, struct ctl_table_header *q)

{

	struct ctl_table *to = p->ctl_table, *by = q->ctl_table;

	struct ctl_table *next;

	int is_better = 0;

	int not_in_parent = !p->attached_by;



	while ((next = is_branch_in(by, to)) != NULL) {

		if (by == q->attached_by)

			is_better = 1;

		if (to == p->attached_by)

			not_in_parent = 1;

		by = by->child;

		to = next->child;

	}



	if (is_better && not_in_parent) {

		q->attached_by = by;

		q->attached_to = to;

		q->parent = p;

	}

}



#ifdef CONFIG_SYSCTL_SYSCALL_CHECK

static int sysctl_depth(struct ctl_table *table)

{

	struct ctl_table *tmp;

	int depth;



	depth = 0;

	for (tmp = table; tmp->parent; tmp = tmp->parent)

		depth++;



	return depth;

}



static struct ctl_table *sysctl_parent(struct ctl_table *table, int n)

{

	int i;



	for (i = 0; table && i < n; i++)

		table = table->parent;



	return table;

}





static void sysctl_print_path(struct ctl_table *table)

{

	struct ctl_table *tmp;

	int depth, i;

	depth = sysctl_depth(table);

	if (table->procname) {

		for (i = depth; i >= 0; i--) {

			tmp = sysctl_parent(table, i);

			printk("/%s", tmp->procname?tmp->procname:"");

		}

	}

	printk(" ");

}



static struct ctl_table *sysctl_check_lookup(struct nsproxy *namespaces,

						struct ctl_table *table)

{

	struct ctl_table_header *head;

	struct ctl_table *ref, *test;

	int depth, cur_depth;



	depth = sysctl_depth(table);



	for (head = __sysctl_head_next(namespaces, NULL); head;

	     head = __sysctl_head_next(namespaces, head)) {

		cur_depth = depth;

		ref = head->ctl_table;

repeat:

		test = sysctl_parent(table, cur_depth);

		for (; ref->procname; ref++) {

			int match = 0;

			if (cur_depth && !ref->child)

				continue;



			if (test->procname && ref->procname &&

			    (strcmp(test->procname, ref->procname) == 0))

					match++;



			if (match) {

				if (cur_depth != 0) {

					cur_depth--;

					ref = ref->child;

					goto repeat;

				}

				goto out;

			}

		}

	}

	ref = NULL;

out:

	sysctl_head_finish(head);

	return ref;

}



static void set_fail(const char **fail, struct ctl_table *table, const char *str)

{

	if (*fail) {

		printk(KERN_ERR "sysctl table check failed: ");

		sysctl_print_path(table);

		printk(" %s\n", *fail);

		dump_stack();

	}

	*fail = str;

}



static void sysctl_check_leaf(struct nsproxy *namespaces,

				struct ctl_table *table, const char **fail)

{

	struct ctl_table *ref;



	ref = sysctl_check_lookup(namespaces, table);

	if (ref && (ref != table))

		set_fail(fail, table, "Sysctl already exists");

}



static int sysctl_check_table(struct nsproxy *namespaces, struct ctl_table *table)

{

	int error = 0;

	for (; table->procname; table++) {

		const char *fail = NULL;



		if (table->parent) {

			if (!table->parent->procname)

				set_fail(&fail, table, "Parent without procname");

		}

		if (table->child) {

			if (table->data)

				set_fail(&fail, table, "Directory with data?");

			if (table->maxlen)

				set_fail(&fail, table, "Directory with maxlen?");

			if ((table->mode & (S_IRUGO|S_IXUGO)) != table->mode)

				set_fail(&fail, table, "Writable sysctl directory");

			if (table->proc_handler)

				set_fail(&fail, table, "Directory with proc_handler");

			if (table->extra1)

				set_fail(&fail, table, "Directory with extra1");

			if (table->extra2)

				set_fail(&fail, table, "Directory with extra2");

		} else {

			if ((table->proc_handler == proc_dostring) ||

			    (table->proc_handler == proc_dointvec) ||

			    (table->proc_handler == proc_dointvec_minmax) ||

			    (table->proc_handler == proc_dointvec_jiffies) ||

			    (table->proc_handler == proc_dointvec_userhz_jiffies) ||

			    (table->proc_handler == proc_dointvec_ms_jiffies) ||

			    (table->proc_handler == proc_doulongvec_minmax) ||

			    (table->proc_handler == proc_doulongvec_ms_jiffies_minmax)) {

				if (!table->data)

					set_fail(&fail, table, "No data");

				if (!table->maxlen)

					set_fail(&fail, table, "No maxlen");

			}

#ifdef CONFIG_PROC_SYSCTL

			if (!table->proc_handler)

				set_fail(&fail, table, "No proc_handler");

#endif

			sysctl_check_leaf(namespaces, table, &fail);

		}

		if (table->mode > 0777)

			set_fail(&fail, table, "bogus .mode");

		if (fail) {

			set_fail(&fail, table, NULL);

			error = -EINVAL;

		}

		if (table->child)

			error |= sysctl_check_table(namespaces, table->child);

	}

	return error;

}

#endif /* CONFIG_SYSCTL_SYSCALL_CHECK */



/**

 * __register_sysctl_paths - register a sysctl hierarchy

 * @root: List of sysctl headers to register on

 * @namespaces: Data to compute which lists of sysctl entries are visible

 * @path: The path to the directory the sysctl table is in.

 * @table: the top-level table structure

 *

 * Register a sysctl table hierarchy. @table should be a filled in ctl_table

 * array. A completely 0 filled entry terminates the table.

 *

 * The members of the &struct ctl_table structure are used as follows:

 *

 * procname - the name of the sysctl file under /proc/sys. Set to %NULL to not

 *            enter a sysctl file

 *

 * data - a pointer to data for use by proc_handler

 *

 * maxlen - the maximum size in bytes of the data

 *

 * mode - the file permissions for the /proc/sys file, and for sysctl(2)

 *

 * child - a pointer to the child sysctl table if this entry is a directory, or

 *         %NULL.

 *

 * proc_handler - the text handler routine (described below)

 *

 * de - for internal use by the sysctl routines

 *

 * extra1, extra2 - extra pointers usable by the proc handler routines

 *

 * Leaf nodes in the sysctl tree will be represented by a single file

 * under /proc; non-leaf nodes will be represented by directories.

 *

 * sysctl(2) can automatically manage read and write requests through

 * the sysctl table.  The data and maxlen fields of the ctl_table

 * struct enable minimal validation of the values being written to be

 * performed, and the mode field allows minimal authentication.

 *

 * There must be a proc_handler routine for any terminal nodes

 * mirrored under /proc/sys (non-terminals are handled by a built-in

 * directory handler).  Several default handlers are available to

 * cover common cases -

 *

 * proc_dostring(), proc_dointvec(), proc_dointvec_jiffies(),

 * proc_dointvec_userhz_jiffies(), proc_dointvec_minmax(),

 * proc_doulongvec_ms_jiffies_minmax(), proc_doulongvec_minmax()

 *

 * It is the handler's job to read the input buffer from user memory

 * and process it. The handler should return 0 on success.

 *

 * This routine returns %NULL on a failure to register, and a pointer

 * to the table header on success.

 */

struct ctl_table_header *__register_sysctl_paths(

	struct ctl_table_root *root,

	struct nsproxy *namespaces,

	const struct ctl_path *path, struct ctl_table *table)

{

	struct ctl_table_header *header;

	struct ctl_table *new, **prevp;

	unsigned int n, npath;

	struct ctl_table_set *set;



	/* Count the path components */

	for (npath = 0; path[npath].procname; ++npath)

		;



	/*

	 * For each path component, allocate a 2-element ctl_table array.

	 * The first array element will be filled with the sysctl entry

	 * for this, the second will be the sentinel (procname == 0).

	 *

	 * We allocate everything in one go so that we don't have to

	 * worry about freeing additional memory in unregister_sysctl_table.

	 */

	header = kzalloc(sizeof(struct ctl_table_header) +

			 (2 * npath * sizeof(struct ctl_table)), GFP_KERNEL);

	if (!header)

		return NULL;



	new = (struct ctl_table *) (header + 1);



	/* Now connect the dots */

	prevp = &header->ctl_table;

	for (n = 0; n < npath; ++n, ++path) {

		/* Copy the procname */

		new->procname = path->procname;

		new->mode     = 0555;



		*prevp = new;

		prevp = &new->child;



		new += 2;

	}

	*prevp = table;

	header->ctl_table_arg = table;



	INIT_LIST_HEAD(&header->ctl_entry);

	header->used = 0;

	header->unregistering = NULL;

	header->root = root;

	sysctl_set_parent(NULL, header->ctl_table);

	header->count = 1;

#ifdef CONFIG_SYSCTL_SYSCALL_CHECK

	if (sysctl_check_table(namespaces, header->ctl_table)) {

		kfree(header);

		return NULL;

	}

#endif

	spin_lock(&sysctl_lock);

	header->set = lookup_header_set(root, namespaces);

	header->attached_by = header->ctl_table;

	header->attached_to = root_table;

	header->parent = &root_table_header;

	for (set = header->set; set; set = set->parent) {

		struct ctl_table_header *p;

		list_for_each_entry(p, &set->list, ctl_entry) {

			if (p->unregistering)

				continue;

			try_attach(p, header);

		}

	}

	header->parent->count++;

	list_add_tail(&header->ctl_entry, &header->set->list);

	spin_unlock(&sysctl_lock);



	return header;

}



/**

 * register_sysctl_table_path - register a sysctl table hierarchy

 * @path: The path to the directory the sysctl table is in.

 * @table: the top-level table structure

 *

 * Register a sysctl table hierarchy. @table should be a filled in ctl_table

 * array. A completely 0 filled entry terminates the table.

 *

 * See __register_sysctl_paths for more details.

 */

struct ctl_table_header *register_sysctl_paths(const struct ctl_path *path,

						struct ctl_table *table)

{

	return __register_sysctl_paths(&sysctl_table_root, current->nsproxy,

					path, table);

}

EXPORT_SYMBOL(register_sysctl_paths);



/**

 * register_sysctl_table - register a sysctl table hierarchy

 * @table: the top-level table structure

 *

 * Register a sysctl table hierarchy. @table should be a filled in ctl_table

 * array. A completely 0 filled entry terminates the table.

 *

 * See register_sysctl_paths for more details.

 */

struct ctl_table_header *register_sysctl_table(struct ctl_table *table)

{

	static const struct ctl_path null_path[] = { {} };



	return register_sysctl_paths(null_path, table);

}

EXPORT_SYMBOL(register_sysctl_table);



/**

 * unregister_sysctl_table - unregister a sysctl table hierarchy

 * @header: the header returned from register_sysctl_table

 *

 * Unregisters the sysctl table and all children. proc entries may not

 * actually be removed until they are no longer used by anyone.

 */

void unregister_sysctl_table(struct ctl_table_header * header)

{

	might_sleep();



	if (header == NULL)

		return;



	spin_lock(&sysctl_lock);

	start_unregistering(header);

	if (!--header->parent->count) {

		WARN_ON(1);

		kfree_rcu(header->parent, rcu);

	}

	if (!--header->count)

		kfree_rcu(header, rcu);

	spin_unlock(&sysctl_lock);

}

EXPORT_SYMBOL(unregister_sysctl_table);



void setup_sysctl_set(struct ctl_table_set *p,

	struct ctl_table_set *parent,

	int (*is_seen)(struct ctl_table_set *))

{

	INIT_LIST_HEAD(&p->list);

	p->parent = parent ? parent : &sysctl_table_root.default_set;

	p->is_seen = is_seen;

}





int __init proc_sys_init(void)

{

	struct proc_dir_entry *proc_sys_root;

include/linux/sysctl.h

+0 −16
Original line number Diff line number Diff line
@@ -1073,17 +1073,6 @@ extern void setup_sysctl_set(struct ctl_table_set *p, 
	struct ctl_table_set *parent,

	int (*is_seen)(struct ctl_table_set *));



extern void sysctl_head_get(struct ctl_table_header *);

extern void sysctl_head_put(struct ctl_table_header *);

extern int sysctl_is_seen(struct ctl_table_header *);

extern struct ctl_table_header *sysctl_head_grab(struct ctl_table_header *);

extern struct ctl_table_header *sysctl_head_next(struct ctl_table_header *prev);

extern struct ctl_table_header *__sysctl_head_next(struct nsproxy *namespaces,

						struct ctl_table_header *prev);

extern void sysctl_head_finish(struct ctl_table_header *prev);

extern int sysctl_perm(struct ctl_table_root *root,

		struct ctl_table *table, int op);



void register_sysctl_root(struct ctl_table_root *root);

struct ctl_table_header *__register_sysctl_paths(

	struct ctl_table_root *root, struct nsproxy *namespaces,
@@ -1093,7 +1082,6 @@ struct ctl_table_header *register_sysctl_paths(const struct ctl_path *path, 
						struct ctl_table *table);



void unregister_sysctl_table(struct ctl_table_header * table);

int sysctl_check_table(struct nsproxy *namespaces, struct ctl_table *table);



extern int sysctl_init(void);

#else /* CONFIG_SYSCTL */
@@ -1118,10 +1106,6 @@ static inline void setup_sysctl_set(struct ctl_table_set *p, 
{

}



static inline void sysctl_head_put(struct ctl_table_header *head)

{

}



#endif /* CONFIG_SYSCTL */



#endif /* __KERNEL__ */

kernel/Makefile

+0 −1
Original line number Diff line number Diff line
@@ -27,7 +27,6 @@ obj-y += power/ 


obj-$(CONFIG_FREEZER) += freezer.o

obj-$(CONFIG_PROFILING) += profile.o

obj-$(CONFIG_SYSCTL_SYSCALL_CHECK) += sysctl_check.o

obj-$(CONFIG_STACKTRACE) += stacktrace.o

obj-y += time/

obj-$(CONFIG_DEBUG_MUTEXES) += mutex-debug.o

kernel/sysctl.c

+0 −464

File changed.

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