mirror of https://gitee.com/openkylin/linux.git
116 lines
3.0 KiB
C
116 lines
3.0 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* Squashfs - a compressed read only filesystem for Linux
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*
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* Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
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* Phillip Lougher <phillip@squashfs.org.uk>
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*
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* id.c
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*/
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/*
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* This file implements code to handle uids and gids.
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*
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* For space efficiency regular files store uid and gid indexes, which are
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* converted to 32-bit uids/gids using an id look up table. This table is
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* stored compressed into metadata blocks. A second index table is used to
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* locate these. This second index table for speed of access (and because it
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* is small) is read at mount time and cached in memory.
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*/
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#include <linux/fs.h>
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#include <linux/vfs.h>
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#include <linux/slab.h>
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#include "squashfs_fs.h"
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#include "squashfs_fs_sb.h"
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#include "squashfs.h"
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/*
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* Map uid/gid index into real 32-bit uid/gid using the id look up table
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*/
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int squashfs_get_id(struct super_block *sb, unsigned int index,
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unsigned int *id)
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{
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struct squashfs_sb_info *msblk = sb->s_fs_info;
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int block = SQUASHFS_ID_BLOCK(index);
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int offset = SQUASHFS_ID_BLOCK_OFFSET(index);
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u64 start_block;
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__le32 disk_id;
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int err;
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if (index >= msblk->ids)
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return -EINVAL;
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start_block = le64_to_cpu(msblk->id_table[block]);
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err = squashfs_read_metadata(sb, &disk_id, &start_block, &offset,
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sizeof(disk_id));
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if (err < 0)
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return err;
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*id = le32_to_cpu(disk_id);
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return 0;
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}
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/*
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* Read uncompressed id lookup table indexes from disk into memory
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*/
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__le64 *squashfs_read_id_index_table(struct super_block *sb,
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u64 id_table_start, u64 next_table, unsigned short no_ids)
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{
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unsigned int length = SQUASHFS_ID_BLOCK_BYTES(no_ids);
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unsigned int indexes = SQUASHFS_ID_BLOCKS(no_ids);
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int n;
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__le64 *table;
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u64 start, end;
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TRACE("In read_id_index_table, length %d\n", length);
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/* Sanity check values */
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/* there should always be at least one id */
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if (no_ids == 0)
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return ERR_PTR(-EINVAL);
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/*
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* The computed size of the index table (length bytes) should exactly
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* match the table start and end points
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*/
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if (length != (next_table - id_table_start))
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return ERR_PTR(-EINVAL);
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table = squashfs_read_table(sb, id_table_start, length);
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if (IS_ERR(table))
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return table;
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/*
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* table[0], table[1], ... table[indexes - 1] store the locations
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* of the compressed id blocks. Each entry should be less than
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* the next (i.e. table[0] < table[1]), and the difference between them
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* should be SQUASHFS_METADATA_SIZE or less. table[indexes - 1]
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* should be less than id_table_start, and again the difference
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* should be SQUASHFS_METADATA_SIZE or less
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*/
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for (n = 0; n < (indexes - 1); n++) {
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start = le64_to_cpu(table[n]);
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end = le64_to_cpu(table[n + 1]);
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if (start >= end || (end - start) >
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(SQUASHFS_METADATA_SIZE + SQUASHFS_BLOCK_OFFSET)) {
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kfree(table);
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return ERR_PTR(-EINVAL);
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}
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}
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start = le64_to_cpu(table[indexes - 1]);
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if (start >= id_table_start || (id_table_start - start) >
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(SQUASHFS_METADATA_SIZE + SQUASHFS_BLOCK_OFFSET)) {
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kfree(table);
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return ERR_PTR(-EINVAL);
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}
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return table;
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}
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