// 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>
 *
 * id.c
 */

/*
 * This file implements code to handle uids and gids.
 *
 * For space efficiency regular files store uid and gid indexes, which are
 * converted to 32-bit uids/gids using an id look up table.  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.
 */

#include <linux/fs.h>
#include <linux/vfs.h>
#include <linux/slab.h>

#include "squashfs_fs.h"
#include "squashfs_fs_sb.h"
#include "squashfs.h"

/*
 * Map uid/gid index into real 32-bit uid/gid using the id look up table
 */
int squashfs_get_id(struct super_block *sb, unsigned int index,
                                        unsigned int *id)
{
        struct squashfs_sb_info *msblk = sb->s_fs_info;
        int block = SQUASHFS_ID_BLOCK(index);
        int offset = SQUASHFS_ID_BLOCK_OFFSET(index);
        u64 start_block;
        __le32 disk_id;
        int err;

        if (index >= msblk->ids)
                return -EINVAL;

        start_block = le64_to_cpu(msblk->id_table[block]);

        err = squashfs_read_metadata(sb, &disk_id, &start_block, &offset,
                                                        sizeof(disk_id));
        if (err < 0)
                return err;

        *id = le32_to_cpu(disk_id);
        return 0;
}


/*
 * Read uncompressed id lookup table indexes from disk into memory
 */
__le64 *squashfs_read_id_index_table(struct super_block *sb,
                u64 id_table_start, u64 next_table, unsigned short no_ids)
{
        unsigned int length = SQUASHFS_ID_BLOCK_BYTES(no_ids);
        unsigned int indexes = SQUASHFS_ID_BLOCKS(no_ids);
        int n;
        __le64 *table;
        u64 start, end;

        TRACE("In read_id_index_table, length %d\n", length);

        /* Sanity check values */

        /* there should always be at least one id */
        if (no_ids == 0)
                return ERR_PTR(-EINVAL);

        /*
         * The computed size of the index table (length bytes) should exactly
         * match the table start and end points
         */
        if (length != (next_table - id_table_start))
                return ERR_PTR(-EINVAL);

        table = squashfs_read_table(sb, id_table_start, length);
        if (IS_ERR(table))
                return table;

        /*
         * table[0], table[1], ... table[indexes - 1] store the locations
         * of the compressed id 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 id_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 >= id_table_start || (id_table_start - start) >
                                (SQUASHFS_METADATA_SIZE + SQUASHFS_BLOCK_OFFSET)) {
                kfree(table);
                return ERR_PTR(-EINVAL);
        }

        return table;
}