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// 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 = {
.fh_to_dentry = squashfs_fh_to_dentry,
.fh_to_parent = squashfs_fh_to_parent,
.get_parent = squashfs_get_parent
};
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