open.c

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

#include <linux/string.h>
#include <linux/mm.h>
#include <linux/utime.h>
#include <linux/file.h>
#include <linux/smp_lock.h>
#include <linux/quotaops.h>
#include <linux/dnotify.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/tty.h>
#include <linux/iobuf.h>

#include <asm/uaccess.h>

#define special_file(m) (S_ISCHR(m)||S_ISBLK(m)||S_ISFIFO(m)||S_ISSOCK(m))

int vfs_statfs(struct super_block *sb, struct statfs *buf)
{
	int retval = -ENODEV;

	if (sb) {
		retval = -ENOSYS;
		if (sb->s_op && sb->s_op->statfs) {
			memset(buf, 0, sizeof(struct statfs));
			lock_kernel();
			retval = sb->s_op->statfs(sb, buf);
			unlock_kernel();
		}
	}
	return retval;
}


asmlinkage long sys_statfs(const char * path, struct statfs * buf)
{
	struct nameidata nd;
	int error;

	error = user_path_walk(path, &nd);
	if (!error) {
		struct statfs tmp;
		error = vfs_statfs(nd.dentry->d_inode->i_sb, &tmp);
		if (!error && copy_to_user(buf, &tmp, sizeof(struct statfs)))
			error = -EFAULT;
		path_release(&nd);
	}
	return error;
}

asmlinkage long sys_fstatfs(unsigned int fd, struct statfs * buf)
{
	struct file * file;
	struct statfs tmp;
	int error;

	error = -EBADF;
	file = fget(fd);
	if (!file)
		goto out;
	error = vfs_statfs(file->f_dentry->d_inode->i_sb, &tmp);
	if (!error && copy_to_user(buf, &tmp, sizeof(struct statfs)))
		error = -EFAULT;
	fput(file);
out:
	return error;
}

int do_truncate(struct dentry *dentry, loff_t length)
{
	struct inode *inode = dentry->d_inode;
	int error;
	struct iattr newattrs;

	/* Not pretty: "inode->i_size" shouldn't really be signed. But it is. */
	if (length < 0)
		return -EINVAL;

	down(&inode->i_sem);
	newattrs.ia_size = length;
	newattrs.ia_valid = ATTR_SIZE | ATTR_CTIME;
	error = notify_change(dentry, &newattrs);
	up(&inode->i_sem);
	return error;
}

static inline long do_sys_truncate(const char * path, loff_t length)
{
	struct nameidata nd;
	struct inode * inode;
	int error;

	error = -EINVAL;
	if (length < 0)	/* sorry, but loff_t says... */
		goto out;

	error = user_path_walk(path, &nd);
	if (error)
		goto out;
	inode = nd.dentry->d_inode;

	/* For directories it's -EISDIR, for other non-regulars - -EINVAL */
	error = -EISDIR;
	if (S_ISDIR(inode->i_mode))
		goto dput_and_out;

	error = -EINVAL;
	if (!S_ISREG(inode->i_mode))
		goto dput_and_out;

	error = permission(inode,MAY_WRITE);
	if (error)
		goto dput_and_out;

	error = -EROFS;
	if (IS_RDONLY(inode))
		goto dput_and_out;

	error = -EPERM;
	if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
		goto dput_and_out;

	/*
	 * Make sure that there are no leases.
	 */
	error = get_lease(inode, FMODE_WRITE);
	if (error)
		goto dput_and_out;

	error = get_write_access(inode);
	if (error)
		goto dput_and_out;

	error = locks_verify_truncate(inode, NULL, length);
	if (!error) {
		DQUOT_INIT(inode);
		error = do_truncate(nd.dentry, length);
	}
	put_write_access(inode);

dput_and_out:
	path_release(&nd);
out:
	return error;
}

asmlinkage long sys_truncate(const char * path, unsigned long length)
{
	/* on 32-bit boxen it will cut the range 2^31--2^32-1 off */
	return do_sys_truncate(path, (long)length);
}

static inline long do_sys_ftruncate(unsigned int fd, loff_t length, int small)
{
	struct inode * inode;
	struct dentry *dentry;
	struct file * file;
	int error;

	error = -EINVAL;
	if (length < 0)
		goto out;
	error = -EBADF;
	file = fget(fd);
	if (!file)
		goto out;

	/* explicitly opened as large or we are on 64-bit box */
	if (file->f_flags & O_LARGEFILE)
		small = 0;

	dentry = file->f_dentry;
	inode = dentry->d_inode;
	error = -EINVAL;
	if (!S_ISREG(inode->i_mode) || !(file->f_mode & FMODE_WRITE))
		goto out_putf;

	error = -EINVAL;
	/* Cannot ftruncate over 2^31 bytes without large file support */
	if (small && length > MAX_NON_LFS)
		goto out_putf;

	error = -EPERM;
	if (IS_APPEND(inode))
		goto out_putf;

	error = locks_verify_truncate(inode, file, length);
	if (!error)
		error = do_truncate(dentry, length);
out_putf:
	fput(file);
out:
	return error;
}

asmlinkage long sys_ftruncate(unsigned int fd, unsigned long length)
{
	return do_sys_ftruncate(fd, length, 1);
}

/* LFS versions of truncate are only needed on 32 bit machines */
#if BITS_PER_LONG == 32
asmlinkage long sys_truncate64(const char * path, loff_t length)
{
	return do_sys_truncate(path, length);
}

asmlinkage long sys_ftruncate64(unsigned int fd, loff_t length)
{
	return do_sys_ftruncate(fd, length, 0);
}
#endif

#if !(defined(__alpha__) || defined(__ia64__))

/*
 * sys_utime() can be implemented in user-level using sys_utimes().
 * Is this for backwards compatibility?  If so, why not move it
 * into the appropriate arch directory (for those architectures that
 * need it).
 */

/* If times==NULL, set access and modification to current time,
 * must be owner or have write permission.
 * Else, update from *times, must be owner or super user.
 */
asmlinkage long sys_utime(char * filename, struct utimbuf * times)
{
	int error;
	struct nameidata nd;
	struct inode * inode;
	struct iattr newattrs;

	error = user_path_walk(filename, &nd);
	if (error)
		goto out;
	inode = nd.dentry->d_inode;

	error = -EROFS;
	if (IS_RDONLY(inode))
		goto dput_and_out;

	/* Don't worry, the checks are done in inode_change_ok() */
	newattrs.ia_valid = ATTR_CTIME | ATTR_MTIME | ATTR_ATIME;
	if (times) {
		error = get_user(newattrs.ia_atime, &times->actime);
		if (!error) 
			error = get_user(newattrs.ia_mtime, &times->modtime);
		if (error)
			goto dput_and_out;

		newattrs.ia_valid |= ATTR_ATIME_SET | ATTR_MTIME_SET;
	} else {
		if (current->fsuid != inode->i_uid &&
		    (error = permission(inode,MAY_WRITE)) != 0)
			goto dput_and_out;
	}
	error = notify_change(nd.dentry, &newattrs);
dput_and_out:
	path_release(&nd);
out:
	return error;
}

#endif

/* If times==NULL, set access and modification to current time,
 * must be owner or have write permission.
 * Else, update from *times, must be owner or super user.
 */
asmlinkage long sys_utimes(char * filename, struct timeval * utimes)
{
	int error;
	struct nameidata nd;
	struct inode * inode;
	struct iattr newattrs;

	error = user_path_walk(filename, &nd);

	if (error)
		goto out;
	inode = nd.dentry->d_inode;

	error = -EROFS;
	if (IS_RDONLY(inode))
		goto dput_and_out;

	/* Don't worry, the checks are done in inode_change_ok() */
	newattrs.ia_valid = ATTR_CTIME | ATTR_MTIME | ATTR_ATIME;
	if (utimes) {
		struct timeval times[2];
		error = -EFAULT;
		if (copy_from_user(&times, utimes, sizeof(times)))
			goto dput_and_out;
		newattrs.ia_atime = times[0].tv_sec;
		newattrs.ia_mtime = times[1].tv_sec;
		newattrs.ia_valid |= ATTR_ATIME_SET | ATTR_MTIME_SET;
	} else {
		if ((error = permission(inode,MAY_WRITE)) != 0)
			goto dput_and_out;
	}
	error = notify_change(nd.dentry, &newattrs);
dput_and_out:
	path_release(&nd);
out:
	return error;
}

/*
 * access() needs to use the real uid/gid, not the effective uid/gid.
 * We do this by temporarily clearing all FS-related capabilities and
 * switching the fsuid/fsgid around to the real ones.
 */
asmlinkage long sys_access(const char * filename, int mode)
{
	struct nameidata nd;
	int old_fsuid, old_fsgid;
	kernel_cap_t old_cap;
	int res;

	if (mode & ~S_IRWXO)	/* where's F_OK, X_OK, W_OK, R_OK? */
		return -EINVAL;

	old_fsuid = current->fsuid;
	old_fsgid = current->fsgid;
	old_cap = current->cap_effective;

	current->fsuid = current->uid;
	current->fsgid = current->gid;

	/* Clear the capabilities if we switch to a non-root user */
	if (current->uid)
		cap_clear(current->cap_effective);
	else
		current->cap_effective = current->cap_permitted;

	res = user_path_walk(filename, &nd);
	if (!res) {
		res = permission(nd.dentry->d_inode, mode);
		/* SuS v2 requires we report a read only fs too */
		if(!res && (mode & S_IWOTH) && IS_RDONLY(nd.dentry->d_inode)
		   && !special_file(nd.dentry->d_inode->i_mode))
			res = -EROFS;
		path_release(&nd);
	}

	current->fsuid = old_fsuid;
	current->fsgid = old_fsgid;
	current->cap_effective = old_cap;

	return res;
}

asmlinkage long sys_chdir(const char * filename)
{
	int error;
	struct nameidata nd;
	char *name;

	name = getname(filename);
	error = PTR_ERR(name);
	if (IS_ERR(name))
		goto out;

	error = 0;
	if (path_init(name,LOOKUP_POSITIVE|LOOKUP_FOLLOW|LOOKUP_DIRECTORY,&nd))
		error = path_walk(name, &nd);
	putname(name);
	if (error)
		goto out;

	error = permission(nd.dentry->d_inode,MAY_EXEC);
	if (error)
		goto dput_and_out;

	set_fs_pwd(current->fs, nd.mnt, nd.dentry);

dput_and_out:
	path_release(&nd);
out:
	return error;
}

asmlinkage long sys_fchdir(unsigned int fd)
{
	struct file *file;
	struct dentry *dentry;
	struct inode *inode;
	struct vfsmount *mnt;
	int error;

	error = -EBADF;
	file = fget(fd);
	if (!file)
		goto out;

	dentry = file->f_dentry;
	mnt = file->f_vfsmnt;
	inode = dentry->d_inode;

	error = -ENOTDIR;
	if (!S_ISDIR(inode->i_mode))
		goto out_putf;

	error = permission(inode, MAY_EXEC);
	if (!error)
		set_fs_pwd(current->fs, mnt, dentry);
out_putf:
	fput(file);
out:
	return error;
}

asmlinkage long sys_chroot(const char * filename)
{
	int error;
	struct nameidata nd;
	char *name;

	name = getname(filename);
	error = PTR_ERR(name);
	if (IS_ERR(name))
		goto out;

	path_init(name, LOOKUP_POSITIVE | LOOKUP_FOLLOW |
		      LOOKUP_DIRECTORY | LOOKUP_NOALT, &nd);
	error = path_walk(name, &nd);	
	putname(name);
	if (error)
		goto out;

	error = permission(nd.dentry->d_inode,MAY_EXEC);
	if (error)
		goto dput_and_out;

	error = -EPERM;
	if (!capable(CAP_SYS_CHROOT))
		goto dput_and_out;

	set_fs_root(current->fs, nd.mnt, nd.dentry);
	set_fs_altroot();
	error = 0;
dput_and_out: