path: root/fs/overlayfs/inode.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 *
 * Copyright (C) 2011 Novell Inc.
 */

#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/cred.h>
#include <linux/xattr.h>
#include <linux/posix_acl.h>
#include <linux/ratelimit.h>
#include <linux/fiemap.h>
#include <linux/fileattr.h>
#include <linux/security.h>
#include <linux/namei.h>
#include "overlayfs.h"


int ovl_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
		struct iattr *attr)
{
	int err;
	bool full_copy_up = false;
	struct dentry *upperdentry;
	const struct cred *old_cred;

	err = setattr_prepare(&init_user_ns, dentry, attr);
	if (err)
		return err;

	err = ovl_want_write(dentry);
	if (err)
		goto out;

	if (attr->ia_valid & ATTR_SIZE) {
		/* Truncate should trigger data copy up as well */
		full_copy_up = true;
	}

	if (!full_copy_up)
		err = ovl_copy_up(dentry);
	else
		err = ovl_copy_up_with_data(dentry);
	if (!err) {
		struct inode *winode = NULL;

		upperdentry = ovl_dentry_upper(dentry);

		if (attr->ia_valid & ATTR_SIZE) {
			winode = d_inode(upperdentry);
			err = get_write_access(winode);
			if (err)
				goto out_drop_write;
		}

		if (attr->ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID))
			attr->ia_valid &= ~ATTR_MODE;

		/*
		 * We might have to translate ovl file into real file object
		 * once use cases emerge.  For now, simply don't let underlying
		 * filesystem rely on attr->ia_file
		 */
		attr->ia_valid &= ~ATTR_FILE;

		/*
		 * If open(O_TRUNC) is done, VFS calls ->setattr with ATTR_OPEN
		 * set.  Overlayfs does not pass O_TRUNC flag to underlying
		 * filesystem during open -> do not pass ATTR_OPEN.  This
		 * disables optimization in fuse which assumes open(O_TRUNC)
		 * already set file size to 0.  But we never passed O_TRUNC to
		 * fuse.  So by clearing ATTR_OPEN, fuse will be forced to send
		 * setattr request to server.
		 */
		attr->ia_valid &= ~ATTR_OPEN;

		inode_lock(upperdentry->d_inode);
		old_cred = ovl_override_creds(dentry->d_sb);
		err = notify_change(&init_user_ns, upperdentry, attr, NULL);
		revert_creds(old_cred);
		if (!err)
			ovl_copyattr(upperdentry->d_inode, dentry->d_inode);
		inode_unlock(upperdentry->d_inode);

		if (winode)
			put_write_access(winode);
	}
out_drop_write:
	ovl_drop_write(dentry);
out:
	return err;
}

static void ovl_map_dev_ino(struct dentry *dentry, struct kstat *stat, int fsid)
{
	bool samefs = ovl_same_fs(dentry->d_sb);
	unsigned int xinobits = ovl_xino_bits(dentry->d_sb);
	unsigned int xinoshift = 64 - xinobits;

	if (samefs) {
		/*
		 * When all layers are on the same fs, all real inode
		 * number are unique, so we use the overlay st_dev,
		 * which is friendly to du -x.
		 */
		stat->dev = dentry->d_sb->s_dev;
		return;
	} else if (xinobits) {
		/*
		 * All inode numbers of underlying fs should not be using the
		 * high xinobits, so we use high xinobits to partition the
		 * overlay st_ino address space. The high bits holds the fsid
		 * (upper fsid is 0). The lowest xinobit is reserved for mapping
		 * the non-persistent inode numbers range in case of overflow.
		 * This way all overlay inode numbers are unique and use the
		 * overlay st_dev.
		 */
		if (likely(!(stat->ino >> xinoshift))) {
			stat->ino |= ((u64)fsid) << (xinoshift + 1);
			stat->dev = dentry->d_sb->s_dev;
			return;
		} else if (ovl_xino_warn(dentry->d_sb)) {
			pr_warn_ratelimited("inode number too big (%pd2, ino=%llu, xinobits=%d)\n",
					    dentry, stat->ino, xinobits);
		}
	}

	/* The inode could not be mapped to a unified st_ino address space */
	if (S_ISDIR(dentry->d_inode->i_mode)) {
		/*
		 * Always use the overlay st_dev for directories, so 'find
		 * -xdev' will scan the entire overlay mount and won't cross the
		 * overlay mount boundaries.
		 *
		 * If not all layers are on the same fs the pair {real st_ino;
		 * overlay st_dev} is not unique, so use the non persistent
		 * overlay st_ino for directories.
		 */
		stat->dev = dentry->d_sb<