path: root/fs/open.c

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

#include <linux/string.h>
#include <linux/mm.h>
#include <linux/file.h>
#include <linux/fdtable.h>
#include <linux/fsnotify.h>
#include <linux/module.h>
#include <linux/tty.h>
#include <linux/namei.h>
#include <linux/backing-dev.h>
#include <linux/capability.h>
#include <linux/securebits.h>
#include <linux/security.h>
#include <linux/mount.h>
#include <linux/fcntl.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/fs.h>
#include <linux/personality.h>
#include <linux/pagemap.h>
#include <linux/syscalls.h>
#include <linux/rcupdate.h>
#include <linux/audit.h>
#include <linux/falloc.h>
#include <linux/fs_struct.h>
#include <linux/ima.h>
#include <linux/dnotify.h>
#include <linux/compat.h>

#include "internal.h"

int do_truncate(struct dentry *dentry, loff_t length, unsigned int time_attrs,
	struct file *filp)
{
	int ret;
	struct iattr newattrs;

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

	newattrs.ia_size = length;
	newattrs.ia_valid = ATTR_SIZE | time_attrs;
	if (filp) {
		newattrs.ia_file = filp;
		newattrs.ia_valid |= ATTR_FILE;
	}

	/* Remove suid, sgid, and file capabilities on truncate too */
	ret = dentry_needs_remove_privs(dentry);
	if (ret < 0)
		return ret;
	if (ret)
		newattrs.ia_valid |= ret | ATTR_FORCE;

	inode_lock(dentry->d_inode);
	/* Note any delegations or leases have already been broken: */
	ret = notify_change(dentry, &newattrs, NULL);
	inode_unlock(dentry->d_inode);
	return ret;
}

long vfs_truncate(const struct path *path, loff_t length)
{
	struct inode *inode;
	struct dentry *upperdentry;
	long error;

	inode = path->dentry->d_inode;

	/* For directories it's -EISDIR, for other non-regulars - -EINVAL */
	if (S_ISDIR(inode->i_mode))
		return -EISDIR;
	if (!S_ISREG(inode->i_mode))
		return -EINVAL;

	error = mnt_want_write(path->mnt);
	if (error)
		goto out;

	error = inode_permission(inode, MAY_WRITE);
	if (error)
		goto mnt_drop_write_and_out;

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

	/*
	 * If this is an overlayfs then do as if opening the file so we get
	 * write access on the upper inode, not on the overlay inode.  For
	 * non-overlay filesystems d_real() is an identity function.
	 */
	upperdentry = d_real(path->dentry, NULL, O_WRONLY, 0);
	error = PTR_ERR(upperdentry);
	if (IS_ERR(upperdentry))
		goto mnt_drop_write_and_out;

	error = get_write_access(upperdentry->d_inode);
	if (error)
		goto mnt_drop_write_and_out;

	/*
	 * Make sure that there are no leases.  get_write_access() protects
	 * against the truncate racing with a lease-granting setlease().
	 */
	error = break_lease(inode, O_WRONLY);
	if (error)
		goto put_write_and_out;

	error = locks_verify_truncate(