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Commit 9043476f authored by Al Viro's avatar Al Viro
Browse files

[PATCH] sanitize proc_sysctl 



* keep references to ctl_table_head and ctl_table in /proc/sys inodes
* grab the former during operations, use the latter for access to
  entry if that succeeds
* have ->d_compare() check if table should be seen for one who does lookup;
  that allows us to avoid flipping inodes - if we have the same name resolve
  to different things, we'll just keep several dentries and ->d_compare()
  will reject the wrong ones.
* have ->lookup() and ->readdir() scan the table of our inode first, then
  walk all ctl_table_header and scan ->attached_by for those that are
  attached to our directory.
* implement ->getattr().
* get rid of insane amounts of tree-walking
* get rid of the need to know dentry in ->permission() and of the contortions
  induced by that.

Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent ae7edecc

fs/proc/inode.c

+5 −0
Original line number Diff line number Diff line
@@ -17,6 +17,7 @@ 
#include <linux/init.h>

#include <linux/module.h>

#include <linux/smp_lock.h>

#include <linux/sysctl.h>



#include <asm/system.h>

#include <asm/uaccess.h>
@@ -65,6 +66,8 @@ static void proc_delete_inode(struct inode *inode) 
			module_put(de->owner);

		de_put(de);

	}

	if (PROC_I(inode)->sysctl)

		sysctl_head_put(PROC_I(inode)->sysctl);

	clear_inode(inode);

}
@@ -84,6 +87,8 @@ static struct inode *proc_alloc_inode(struct super_block *sb) 
	ei->fd = 0;

	ei->op.proc_get_link = NULL;

	ei->pde = NULL;

	ei->sysctl = NULL;

	ei->sysctl_entry = NULL;

	inode = &ei->vfs_inode;

	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;

	return inode;

fs/proc/proc_sysctl.c

+192 −235
Original line number Diff line number Diff line
@@ -10,149 +10,110 @@ 
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 const struct file_operations proc_sys_dir_file_operations;

static const struct inode_operations proc_sys_dir_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)

static struct inode *proc_sys_make_inode(struct super_block *sb,

		struct ctl_table_header *head, struct ctl_table *table)

{

	struct inode *inode;

	struct proc_inode *dir_ei, *ei;

	int depth;

	struct proc_inode *ei;



	inode = new_inode(dir->i_sb);

	inode = new_inode(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;



	sysctl_head_get(head);

	ei = PROC_I(inode);

	ei->fd = depth;

	ei->sysctl = head;

	ei->sysctl_entry = table;



	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;

	inode->i_flags |= S_PRIVATE; /* tell selinux to ignore this inode */

	inode->i_mode = table->mode;

	if (!table->child) {

		inode->i_mode |= S_IFREG;

		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);

	} else {

		inode->i_mode |= S_IFDIR;

		inode->i_nlink = 0;

		inode->i_op = &proc_sys_dir_operations;

		inode->i_fop = &proc_sys_dir_file_operations;

	}

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)

static struct ctl_table *find_in_table(struct ctl_table *p, struct qstr *name)

{

	int len;

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

	for ( ; p->ctl_name || p->procname; p++) {



		if (!table->procname)

		if (!p->procname)

			continue;



		len = strlen(table->procname);

		len = strlen(p->procname);

		if (len != name->len)

			continue;



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

		if (memcmp(p->procname, name->name, len) != 0)

			continue;



		/* I have a match */

		return table;

		return p;

	}

	return NULL;

}



static struct ctl_table *proc_sys_lookup_table(struct dentry *dentry,

						struct ctl_table *table)

struct ctl_table_header *grab_header(struct inode *inode)

{

	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;

	if (PROC_I(inode)->sysctl)

		return sysctl_head_grab(PROC_I(inode)->sysctl);

	else

		return sysctl_head_next(NULL);

}

	return table;



}

static struct ctl_table *proc_sys_lookup_entry(struct dentry *dparent,

						struct qstr *name,

						struct ctl_table *table)

static struct dentry *proc_sys_lookup(struct inode *dir, struct dentry *dentry,

					struct nameidata *nd)

{

	table = proc_sys_lookup_table(dparent, table);

	if (table)

		table = proc_sys_lookup_table_one(table, name);

	return table;

	struct ctl_table_header *head = grab_header(dir);

	struct ctl_table *table = PROC_I(dir)->sysctl_entry;

	struct ctl_table_header *h = NULL;

	struct qstr *name = &dentry->d_name;

	struct ctl_table *p;

	struct inode *inode;

	struct dentry *err = ERR_PTR(-ENOENT);



	if (IS_ERR(head))

		return ERR_CAST(head);



	if (table && !table->child) {

		WARN_ON(1);

		goto out;

	}



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;

	table = table ? table->child : head->ctl_table;



	for (head = sysctl_head_next(NULL); head;

			head = sysctl_head_next(head)) {

		table = proc_sys_lookup_entry(parent, name, head->ctl_table);

		if (table)

	p = find_in_table(table, name);

	if (!p) {

		for (h = sysctl_head_next(NULL); h; h = sysctl_head_next(h)) {

			if (h->attached_to != table)

				continue;

			p = find_in_table(h->attached_by, name);

			if (p)

				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)

	if (!p)

		goto out;



	err = ERR_PTR(-ENOMEM);

	inode = proc_sys_make_inode(dir, table);

	inode = proc_sys_make_inode(dir->i_sb, h ? h : head, p);

	if (h)

		sysctl_head_finish(h);



	if (!inode)

		goto out;
@@ -168,22 +129,14 @@ static struct dentry *proc_sys_lookup(struct inode *dir, struct dentry *dentry, 
static ssize_t proc_sys_call_handler(struct file *filp, void __user *buf,

		size_t count, loff_t *ppos, int write)

{

	struct dentry *dentry = filp->f_dentry;

	struct ctl_table_header *head;

	struct ctl_table *table;

	struct inode *inode = filp->f_path.dentry->d_inode;

	struct ctl_table_header *head = grab_header(inode);

	struct ctl_table *table = PROC_I(inode)->sysctl_entry;

	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;

	if (IS_ERR(head))

		return PTR_ERR(head);



	/*

	 * At this point we know that the sysctl was not unregistered
@@ -193,6 +146,11 @@ static ssize_t proc_sys_call_handler(struct file *filp, void __user *buf, 
	if (sysctl_perm(head->root, table, write ? MAY_WRITE : MAY_READ))

		goto out;



	/* if that can happen at all, it should be -EINVAL, not -EISDIR */

	error = -EINVAL;

	if (!table->proc_handler)

		goto out;



	/* careful: calling conventions are nasty here */

	res = count;

	error = table->proc_handler(table, write, filp, buf, &res, ppos);
@@ -218,82 +176,86 @@ static ssize_t proc_sys_write(struct file *filp, const char __user *buf, 




static int proc_sys_fill_cache(struct file *filp, void *dirent,

				filldir_t filldir, struct ctl_table *table)

				filldir_t filldir,

				struct ctl_table_header *head,

				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);

		child = d_alloc(dir, &qname);

		if (child) {

			inode = proc_sys_make_inode(dir->d_sb, head, table);

			if (!inode) {

				dput(child);

				return -ENOMEM;

			} else {

				child->d_op = &proc_sys_dentry_operations;

				d_add(child, inode);

			}

			if (child)

				dput(new);

			else

				child = new;

		} else {

			return -ENOMEM;

		}

	}

	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);

	return !!filldir(dirent, qname.name, qname.len, filp->f_pos, ino, type);

}



static int scan(struct ctl_table_header *head, ctl_table *table,

		unsigned long *pos, struct file *file,

		void *dirent, filldir_t filldir)

{



	for (; table->ctl_name || table->procname; table++, (*pos)++) {

		int res;



		/* Can't do anything without a proc name */

		if (!table->procname)

			continue;



		if (*pos < file->f_pos)

			continue;



		res = proc_sys_fill_cache(file, dirent, filldir, head, table);

		if (res)

			return res;



		file->f_pos = *pos + 1;

	}

	return 0;

}



static int proc_sys_readdir(struct file *filp, void *dirent, filldir_t filldir)

{

	struct dentry *dentry = filp->f_dentry;

	struct dentry *dentry = filp->f_path.dentry;

	struct inode *inode = dentry->d_inode;

	struct ctl_table_header *head = NULL;

	struct ctl_table *table;

	struct ctl_table_header *head = grab_header(inode);

	struct ctl_table *table = PROC_I(inode)->sysctl_entry;

	struct ctl_table_header *h = NULL;

	unsigned long pos;

	int ret;

	int ret = -EINVAL;



	ret = -ENOTDIR;

	if (!S_ISDIR(inode->i_mode))

	if (IS_ERR(head))

		return PTR_ERR(head);



	if (table && !table->child) {

		WARN_ON(1);

		goto out;

	}



	table = table ? table->child : head->ctl_table;



	ret = 0;

	/* Avoid a switch here: arm builds fail with missing __cmpdi2 */
@@ -311,30 +273,17 @@ static int proc_sys_readdir(struct file *filp, void *dirent, filldir_t filldir) 
	}

	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;

	ret = scan(head, table, &pos, filp, dirent, filldir);

	if (ret)

		goto out;



			if (pos < filp->f_pos)

	for (h = sysctl_head_next(NULL); h; h = sysctl_head_next(h)) {

		if (h->attached_to != table)

			continue;



			if (proc_sys_fill_cache(filp, dirent, filldir, table) < 0)

				goto out;

			filp->f_pos = pos + 1;

		ret = scan(h, h->attached_by, &pos, filp, dirent, filldir);

		if (ret) {

			sysctl_head_finish(h);

			break;

		}

	}

	ret = 1;
@@ -349,47 +298,18 @@ static int proc_sys_permission(struct inode *inode, int mask, struct nameidata * 
	 * 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;

	struct ctl_table_header *head = grab_header(inode);

	struct ctl_table *table = PROC_I(inode)->sysctl_entry;

	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 (IS_ERR(head))

		return PTR_ERR(head);



	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 */

	if (!table) /* global root - r-xr-xr-x */

		error = mask & MAY_WRITE ? -EACCES : 0;

	else /* Use the permissions on the sysctl table entry */

		error = sysctl_perm(head->root, table, mask);

out:



	sysctl_head_finish(head);

	return error;

}
@@ -409,33 +329,70 @@ static int proc_sys_setattr(struct dentry *dentry, struct iattr *attr) 
	return error;

}



/* I'm lazy and don't distinguish between files and directories,

 * until access time.

 */

static int proc_sys_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)

{

	struct inode *inode = dentry->d_inode;

	struct ctl_table_header *head = grab_header(inode);

	struct ctl_table *table = PROC_I(inode)->sysctl_entry;



	if (IS_ERR(head))

		return PTR_ERR(head);



	generic_fillattr(inode, stat);

	if (table)

		stat->mode = (stat->mode & S_IFMT) | table->mode;



	sysctl_head_finish(head);

	return 0;

}



static const struct file_operations proc_sys_file_operations = {

	.read		= proc_sys_read,

	.write		= proc_sys_write,

};



static const struct file_operations proc_sys_dir_file_operations = {

	.readdir	= proc_sys_readdir,

};



static const struct inode_operations proc_sys_inode_operations = {

	.permission	= proc_sys_permission,

	.setattr	= proc_sys_setattr,

	.getattr	= proc_sys_getattr,

};



static const struct inode_operations proc_sys_dir_operations = {

	.lookup		= proc_sys_lookup,

	.permission	= proc_sys_permission,

	.setattr	= proc_sys_setattr,

	.getattr	= proc_sys_getattr,

};



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;

	return !PROC_I(dentry->d_inode)->sysctl->unregistering;

}



static int proc_sys_delete(struct dentry *dentry)

{

	return !!PROC_I(dentry->d_inode)->sysctl->unregistering;

}



static int proc_sys_compare(struct dentry *dir, struct qstr *qstr,

			    struct qstr *name)

{

	struct dentry *dentry = container_of(qstr, struct dentry, d_name);

	if (qstr->len != name->len)

		return 1;

	if (memcmp(qstr->name, name->name, name->len))

		return 1;

	return !sysctl_is_seen(PROC_I(dentry->d_inode)->sysctl);

}



static struct dentry_operations proc_sys_dentry_operations = {

	.d_revalidate	= proc_sys_revalidate,

	.d_delete	= proc_sys_delete,

	.d_compare	= proc_sys_compare,

};



static struct proc_dir_entry *proc_sys_root;
@@ -443,8 +400,8 @@ 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->proc_iops = &proc_sys_dir_operations;

	proc_sys_root->proc_fops = &proc_sys_dir_file_operations;

	proc_sys_root->nlink = 0;

	return 0;

}

include/linux/proc_fs.h

+5 −0
Original line number Diff line number Diff line
@@ -282,11 +282,16 @@ union proc_op { 
		struct task_struct *task);

};



struct ctl_table_header;

struct ctl_table;



struct proc_inode {

	struct pid *pid;

	int fd;

	union proc_op op;

	struct proc_dir_entry *pde;

	struct ctl_table_header *sysctl;

	struct ctl_table *sysctl_entry;

	struct inode vfs_inode;

};

include/linux/sysctl.h

+1 −0
Original line number Diff line number Diff line
@@ -961,6 +961,7 @@ struct ctl_table_header; 


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,

kernel/sysctl.c

+15 −0
Original line number Diff line number Diff line
@@ -1932,6 +1932,21 @@ void unregister_sysctl_table(struct ctl_table_header * header) 
	spin_unlock(&sysctl_lock);

}



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;

}



void setup_sysctl_set(struct ctl_table_set *p,

	struct ctl_table_set *parent,

	int (*is_seen)(struct ctl_table_set *))