// SPDX-License-Identifier: GPL-2.0-or-later/* * Squashfs - a compressed read only filesystem for Linux * * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008 * Phillip Lougher <phillip@squashfs.org.uk> * * export.c */ /* * This file implements code to make Squashfs filesystems exportable (NFS etc.) * * The export code uses an inode lookup table to map inode numbers passed in * filehandles to an inode location on disk.  This table is stored compressed * into metadata blocks.  A second index table is used to locate these.  This * second index table for speed of access (and because it is small) is read at * mount time and cached in memory. * * The inode lookup table is used only by the export code, inode disk * locations are directly encoded in directories, enabling direct access * without an intermediate lookup for all operations except the export ops. */ #include <linux/fs.h>#include <linux/vfs.h>#include <linux/dcache.h>#include <linux/exportfs.h>#include <linux/slab.h> #include "squashfs_fs.h"#include "squashfs_fs_sb.h"#include "squashfs_fs_i.h"#include "squashfs.h" /* * Look-up inode number (ino) in table, returning the inode location. */static long long squashfs_inode_lookup(struct super_block *sb, int ino_num){	struct squashfs_sb_info *msblk = sb->s_fs_info;	int blk = SQUASHFS_LOOKUP_BLOCK(ino_num - 1);	int offset = SQUASHFS_LOOKUP_BLOCK_OFFSET(ino_num - 1);	u64 start;	__le64 ino;	int err; 	TRACE("Entered squashfs_inode_lookup, inode_number = %d\n", ino_num); 	if (ino_num == 0 || (ino_num - 1) >= msblk->inodes)		return -EINVAL; 	start = le64_to_cpu(msblk->inode_lookup_table[blk]); 	err = squashfs_read_metadata(sb, &ino, &start, &offset, sizeof(ino));	if (err < 0)		return err; 	TRACE("squashfs_inode_lookup, inode = 0x%llx\n",		(u64) le64_to_cpu(ino)); 	return le64_to_cpu(ino);}  static struct dentry *squashfs_export_iget(struct super_block *sb,	unsigned int ino_num){	long long ino;	struct dentry *dentry = ERR_PTR(-ENOENT); 	TRACE("Entered squashfs_export_iget\n"); 	ino = squashfs_inode_lookup(sb, ino_num);	if (ino >= 0)		dentry = d_obtain_alias(squashfs_iget(sb, ino, ino_num)); 	return dentry;}  static struct dentry *squashfs_fh_to_dentry(struct super_block *sb,		struct fid *fid, int fh_len, int fh_type){	if ((fh_type != FILEID_INO32_GEN && fh_type != FILEID_INO32_GEN_PARENT)			|| fh_len < 2)		return NULL; 	return squashfs_export_iget(sb, fid->i32.ino);}  static struct dentry *squashfs_fh_to_parent(struct super_block *sb,		struct fid *fid, int fh_len, int fh_type){	if (fh_type != FILEID_INO32_GEN_PARENT || fh_len < 4)		return NULL; 	return squashfs_export_iget(sb, fid->i32.parent_ino);}  static struct dentry *squashfs_get_parent(struct dentry *child){	struct inode *inode = d_inode(child);	unsigned int parent_ino = squashfs_i(inode)->parent; 	return squashfs_export_iget(inode->i_sb, parent_ino);}  /* * Read uncompressed inode lookup table indexes off disk into memory */__le64 *squashfs_read_inode_lookup_table(struct super_block *sb,		u64 lookup_table_start, u64 next_table, unsigned int inodes){	unsigned int length = SQUASHFS_LOOKUP_BLOCK_BYTES(inodes);	unsigned int indexes = SQUASHFS_LOOKUP_BLOCKS(inodes);	int n;	__le64 *table;	u64 start, end; 	TRACE("In read_inode_lookup_table, length %d\n", length); 	/* Sanity check values */ 	/* there should always be at least one inode */	if (inodes == 0)		return ERR_PTR(-EINVAL); 	/*	 * The computed size of the lookup table (length bytes) should exactly	 * match the table start and end points	 */	if (length != (next_table - lookup_table_start))		return ERR_PTR(-EINVAL); 	table = squashfs_read_table(sb, lookup_table_start, length);	if (IS_ERR(table))		return table; 	/*	 * table0], table[1], ... table[indexes - 1] store the locations	 * of the compressed inode lookup blocks.  Each entry should be	 * less than the next (i.e. table[0] < table[1]), and the difference	 * between them should be SQUASHFS_METADATA_SIZE or less.	 * table[indexes - 1] should  be less than lookup_table_start, and	 * again the difference should be SQUASHFS_METADATA_SIZE or less	 */	for (n = 0; n < (indexes - 1); n++) {		start = le64_to_cpu(table[n]);		end = le64_to_cpu(table[n + 1]); 		if (start >= end		    || (end - start) >		    (SQUASHFS_METADATA_SIZE + SQUASHFS_BLOCK_OFFSET)) {			kfree(table);			return ERR_PTR(-EINVAL);		}	} 	start = le64_to_cpu(table[indexes - 1]);	if (start >= lookup_table_start ||	    (lookup_table_start - start) >	    (SQUASHFS_METADATA_SIZE + SQUASHFS_BLOCK_OFFSET)) {		kfree(table);		return ERR_PTR(-EINVAL);	} 	return table;}  const struct export_operations squashfs_export_ops = {	.encode_fh = generic_encode_ino32_fh,	.fh_to_dentry = squashfs_fh_to_dentry,	.fh_to_parent = squashfs_fh_to_parent,	.get_parent = squashfs_get_parent};