path: root/fs/proc/inode.c

/*
 *  linux/fs/proc/inode.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 */

#include <linux/sched.h>
#include <linux/proc_fs.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/string.h>
#include <linux/stat.h>
#include <linux/file.h>
#include <linux/locks.h>
#include <linux/limits.h>
#include <linux/config.h>

#include <asm/system.h>
#include <asm/uaccess.h>

extern void free_proc_entry(struct proc_dir_entry *);

struct proc_dir_entry * de_get(struct proc_dir_entry *de)
{
	if (de)
		de->count++;
	return de;
}

/*
 * Decrements the use count and checks for deferred deletion.
 */
void de_put(struct proc_dir_entry *de)
{
	if (de) {
		if (!de->count) {
			printk("de_put: entry %s already free!\n", de->name);
			return;
		}

		if (!--de->count) {
			if (de->deleted) {
				printk("de_put: deferred delete of %s\n",
					de->name);
				free_proc_entry(de);
			}
		}
	}
}

static void proc_put_inode(struct inode *inode)
{
#ifdef CONFIG_SUN_OPENPROMFS_MODULE
	if ((inode->i_ino >= PROC_OPENPROM_FIRST) &&
	    (inode->i_ino <  PROC_OPENPROM_FIRST + PROC_NOPENPROM) &&
	    proc_openprom_use)
		(*proc_openprom_use)(inode, 0);
#endif	
	/*
	 * Kill off unused inodes ... VFS will unhash and
	 * delete the inode if we set i_nlink to zero.
	 */
	if (inode->i_count == 1)
		inode->i_nlink = 0;
}

/*
 * Decrement the use count of the proc_dir_entry.
 */
static void proc_delete_inode(struct inode *inode)
{
	struct proc_dir_entry *de = inode->u.generic_ip;

#if defined(CONFIG_SUN_OPENPROMFS) || defined(CONFIG_SUN_OPENPROMFS_MODULE)
	if ((inode->i_ino >= PROC_OPENPROM_FIRST) &&
	    (inode->i_ino <  PROC_OPENPROM_FIRST + PROC_NOPENPROM))
		return;
#endif	

	if (de) {
		/*
		 * Call the fill_inode hook to release module counts.
		 */
		if (de->fill_inode)
			de->fill_inode(inode, 0);
		de_put(de);
	}
}

static struct super_operations proc_sops = { 
	proc_read_inode,
	proc_write_inode,
	proc_put_inode,
	proc_delete_inode,	/* delete_inode(struct inode *) */
	NULL,
	NULL,
	NULL,
	proc_statfs,
	NULL
};


static int parse_options(char *options,uid_t *uid,gid_t *gid)
{
	char *this_char,*value;

	*uid = current->uid;
	*gid = current->gid;
	if (!options) return 1;
	for (this_char = strtok(options,","); this_char; this_char = strtok(NULL,",")) {
		if ((value = strchr(this_char,'=')) != NULL)
			*value++ = 0;
		if (!strcmp(this_char,"uid")) {
			if (!value || !*value)
				return 0;
			*uid = simple_strtoul(value,&value,0);
			if (*value)
				return 0;
		}
		else if (!strcmp(this_char,"gid")) {
			if (!value || !*value)
				return 0;
			*gid = simple_strtoul(value,&value,0);
			if (*value)
				return 0;
		}
		else return 1;
	}
	return 1;
}

/*
 * The standard rules, copied from fs/namei.c:permission().
 */
static int standard_permission(struct inode *inode, int mask)
{
	int mode = inode->i_mode;

	if ((mask & S_IWOTH) && IS_RDONLY(inode) &&
	    (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
		return -EROFS; /* Nobody gets write access to a read-only fs */
	else if ((mask & S_IWOTH) && IS_IMMUTABLE(inode))
		return -EACCES; /* Nobody gets write access to an immutable file */
	else if (current->fsuid == inode->i_uid)
		mode >>= 6;
	else if (in_group_p(inode->i_gid))
		mode >>= 3;
	if (((mode & mask & 0007) == mask) || fsuser())
		return 0;
	return -EACCES;
}

/* 
 * Set up permission rules for processes looking at other processes.
 * You're not allowed to see a process unless it has the same or more
 * restricted root than your own.  This prevents a chrooted processes
 * from escaping through the /proc entries of less restricted
 * processes, and thus allows /proc to be safely mounted in a chrooted
 * area.
 *
 * Note that root (uid 0) doesn't get permission for this either,
 * since chroot is stronger than root.
 *
 * XXX TODO: use the dentry mechanism to make off-limits procs simply
 * invisible rather than denied?  Does each namespace root get its own
 * dentry tree?
 *
 * This also applies the default permissions checks, as it only adds
 * restrictions.
 *
 * Jeremy Fitzhardinge <jeremy@zip.com.au>
 */
int proc_permission(struct inode *inode, int mask)
{
	struct task_struct *p;
	unsigned long ino = inode->i_ino;
	unsigned long pid;
	struct dentry *de, *base;

	if (standard_permission(inode, mask) != 0)
		return -EACCES;

	/* 
	 * Find the root of the processes being examined (if any).
	 * XXX Surely there's a better way of doing this?
	 */
	if (ino >= PROC_OPENPROM_FIRST && 
	    ino <  PROC_OPENPROM_FIRST + PROC_NOPENPROM)
		return 0;		/* already allowed */

	pid = ino >> 16;
	if (pid == 0)
		return 0;		/* already allowed */
	
	de = NULL;
	base = current->fs->root;

	read_lock(&tasklist_lock);
	p = find_task_by_pid(pid);

	if (p && p->fs)
		de = p->fs->root;
	read_unlock(&tasklist_lock);	/* FIXME! */

	if (p == NULL)
		return -EACCES;		/* ENOENT? */

	if (de == NULL)
	{
		/* kswapd and bdflush don't have proper root or cwd... */
		return -EACCES;
	}
	
	/* XXX locking? */
	for(;;)
	{
		struct dentry *parent;

		if (de == base)
			return 0;	/* already allowed */

		de = de->d_covers;
		parent = de->d_parent;

		if (de == parent)
			break;

		de = parent;
	}

	return -EACCES;			/* incompatible roots */
}

struct inode * proc_get_inode(struct super_block * sb, int ino,
				struct proc_dir_entry * de)
{
	struct inode * inode;

	/*
	 * Increment the use count so the dir entry can't disappear.
	 */
	de_get(de);
#if 1
/* shouldn't ever happen */
if (de && de->deleted)
printk("proc_iget: using deleted entry %s, count=%d\n", de->name, de->count);
#endif

	inode = iget(sb, ino);
	if (!inode)
		goto out_fail;
	
#ifdef CONFIG_SUN_OPENPROMFS_MODULE
	if ((inode->i_ino >= PROC_OPENPROM_FIRST)
	    && (inode->i_ino < PROC_OPENPROM_FIRST + PROC_NOPENPROM)
	    && proc_openprom_use)
		(*proc_openprom_use)(inode, 1);
#endif	
	/* N.B. How can this test ever fail?? */
	if (inode->i_sb != sb)
		printk("proc_get_inode: inode fubar\n");

	inode->u.generic_ip = (void *) de;
	if (de) {
		if (de->mode) {
			inode->i_mode = de->mode;
			inode->i_uid = de->uid;
			inode->i_gid = de->gid;
		}
		if (de->size)
			inode->i_size = de->size;
		if (de->ops)
			inode->i_op = de->ops;
		if (de->nlink)
			inode->i_nlink = de->nlink;
		/*
		 * The fill_inode routine should use this call 
		 * to increment module counts, if necessary.
		 */
		if (de->fill_inode)
			de->fill_inode(inode, 1);
	}
	/*
	 * Fixup the root inode's nlink value
	 */
	if (inode->i_ino == PROC_ROOT_INO) {
		struct task_struct *p;

		read_lock(&tasklist_lock);
		for_each_task(p) {
			if (p->pid)
				inode->i_nlink++;
		}
		read_unlock(&tasklist_lock);
	}
out:
	return inode;

out_fail:
	de_put(de);
	goto out;
}			

struct super_block *proc_read_super(struct super_block *s,void *data, 
				    int silent)
{
	struct inode * root_inode;

	lock_super(s);
	s->s_blocksize = 1024;
	s->s_blocksize_bits = 10;
	s->s_magic = PROC_SUPER_MAGIC;
	s->s_op = &proc_sops;
	root_inode = proc_get_inode(s, PROC_ROOT_INO, &proc_root);
	if (!root_inode)
		goto out_no_root;
	s->s_root = d_alloc_root(root_inode, NULL);
	if (!s->s_root)
		goto out_no_root;
	parse_options(data, &root_inode->i_uid, &root_inode->i_gid);
	unlock_super(s);
	return s;

out_no_root:
	printk("proc_read_super: get root inode failed\n");
	iput(root_inode);
	s->s_dev = 0;
	unlock_super(s);
	return NULL;
}

int proc_statfs(struct super_block *sb, struct statfs *buf, int bufsiz)
{
	struct statfs tmp;

	tmp.f_type = PROC_SUPER_MAGIC;
	tmp.f_bsize = PAGE_SIZE/sizeof(long);
	tmp.f_blocks = 0;
	tmp.f_bfree = 0;
	tmp.f_bavail = 0;
	tmp.f_files = 0;
	tmp.f_ffree = 0;
	tmp.f_namelen = NAME_MAX;
	return copy_to_user(buf, &tmp, bufsiz) ? -EFAULT : 0;
}

void proc_read_inode(struct inode * inode)
{
	unsigned long ino, pid;
	struct task_struct * p;
	
	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
	inode->i_blocks = 0;
	inode->i_blksize = 1024;
	ino = inode->i_ino;
	if (ino >= PROC_OPENPROM_FIRST && 
	    ino <  PROC_OPENPROM_FIRST + PROC_NOPENPROM)
		goto out;
	inode->i_op = NULL;
	inode->i_mode = 0;
	inode->i_uid = 0;
	inode->i_gid = 0;
	inode->i_nlink = 1;
	inode->i_size = 0;

	pid = ino >> 16;
	if (!pid)
		goto out;

	read_lock(&tasklist_lock);
	p = find_task_by_pid(pid);
	if (!p)
		goto out_unlock;

	ino &= 0x0000ffff;
	if (ino == PROC_PID_INO || p->dumpable) {
		inode->i_uid = p->euid;
		inode->i_gid = p->egid;
	}
	switch (ino >> 8) {
		struct file * file;
	case PROC_PID_FD_DIR:
		ino &= 0xff;
		file = fcheck_task(p, ino);
		if (!file)
			goto out_unlock;

		inode->i_op = &proc_link_inode_operations;
		inode->i_size = 64;
		inode->i_mode = S_IFLNK;
		if (file->f_mode & 1)
			inode->i_mode |= S_IRUSR | S_IXUSR;
		if (file->f_mode & 2)
			inode->i_mode |= S_IWUSR | S_IXUSR;
	}
out_unlock:
	/* Defer unlocking until we're done with the task */
	read_unlock(&tasklist_lock);

out:
	return;
}

void proc_write_inode(struct inode * inode)
{
}