// 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> * * dir.c */ /* * This file implements code to read directories from disk. * * See namei.c for a description of directory organisation on disk. */ #include <linux/fs.h>#include <linux/filelock.h>#include <linux/vfs.h>#include <linux/slab.h> #include "squashfs_fs.h"#include "squashfs_fs_sb.h"#include "squashfs_fs_i.h"#include "squashfs.h" static const unsigned char squashfs_filetype_table[] = {	DT_UNKNOWN, DT_DIR, DT_REG, DT_LNK, DT_BLK, DT_CHR, DT_FIFO, DT_SOCK}; /* * Lookup offset (f_pos) in the directory index, returning the * metadata block containing it. * * If we get an error reading the index then return the part of the index * (if any) we have managed to read - the index isn't essential, just * quicker. */static int get_dir_index_using_offset(struct super_block *sb,	u64 *next_block, int *next_offset, u64 index_start, int index_offset,	int i_count, u64 f_pos){	struct squashfs_sb_info *msblk = sb->s_fs_info;	int err, i, index, length = 0;	unsigned int size;	struct squashfs_dir_index dir_index; 	TRACE("Entered get_dir_index_using_offset, i_count %d, f_pos %lld\n",					i_count, f_pos); 	/*	 * Translate from external f_pos to the internal f_pos.  This	 * is offset by 3 because we invent "." and ".." entries which are	 * not actually stored in the directory.	 */	if (f_pos <= 3)		return f_pos;	f_pos -= 3; 	for (i = 0; i < i_count; i++) {		err = squashfs_read_metadata(sb, &dir_index, &index_start,				&index_offset, sizeof(dir_index));		if (err < 0)			break; 		index = le32_to_cpu(dir_index.index);		if (index > f_pos)			/*			 * Found the index we're looking for.			 */			break; 		size = le32_to_cpu(dir_index.size) + 1; 		/* size should never be larger than SQUASHFS_NAME_LEN */		if (size > SQUASHFS_NAME_LEN)			break; 		err = squashfs_read_metadata(sb, NULL, &index_start,				&index_offset, size);		if (err < 0)			break; 		length = index;		*next_block = le32_to_cpu(dir_index.start_block) +					msblk->directory_table;	} 	*next_offset = (length + *next_offset) % SQUASHFS_METADATA_SIZE; 	/*	 * Translate back from internal f_pos to external f_pos.	 */	return length + 3;}  static int squashfs_readdir(struct file *file, struct dir_context *ctx){	struct inode *inode = file_inode(file);	struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info;	u64 block = squashfs_i(inode)->start + msblk->directory_table;	int offset = squashfs_i(inode)->offset, length, err;	unsigned int inode_number, dir_count, size, type;	struct squashfs_dir_header dirh;	struct squashfs_dir_entry *dire; 	TRACE("Entered squashfs_readdir [%llx:%x]\n", block, offset); 	dire = kmalloc(sizeof(*dire) + SQUASHFS_NAME_LEN + 1, GFP_KERNEL);	if (dire == NULL) {		ERROR("Failed to allocate squashfs_dir_entry\n");		goto finish;	} 	/*	 * Return "." and  ".." entries as the first two filenames in the	 * directory.  To maximise compression these two entries are not	 * stored in the directory, and so we invent them here.	 *	 * It also means that the external f_pos is offset by 3 from the	 * on-disk directory f_pos.	 */	while (ctx->pos < 3) {		char *name;		int i_ino; 		if (ctx->pos == 0) {			name = ".";			size = 1;			i_ino = inode->i_ino;		} else {			name = "..";			size = 2;			i_ino = squashfs_i(inode)->parent;		} 		if (!dir_emit(ctx, name, size, i_ino,				squashfs_filetype_table[1]))			goto finish; 		ctx->pos += size;	} 	length = get_dir_index_using_offset(inode->i_sb, &block, &offset,				squashfs_i(inode)->dir_idx_start,				squashfs_i(inode)->dir_idx_offset,				squashfs_i(inode)->dir_idx_cnt,				ctx->pos); 	while (length < i_size_read(inode)) {		/*		 * Read directory header		 */		err = squashfs_read_metadata(inode->i_sb, &dirh, &block,					&offset, sizeof(dirh));		if (err < 0)			goto failed_read; 		length += sizeof(dirh); 		dir_count = le32_to_cpu(dirh.count) + 1; 		if (dir_count > SQUASHFS_DIR_COUNT)			goto failed_read; 		while (dir_count--) {			/*			 * Read directory entry.			 */			err = squashfs_read_metadata(inode->i_sb, dire, &block,					&offset, sizeof(*dire));			if (err < 0)				goto failed_read; 			size = le16_to_cpu(dire->size) + 1; 			/* size should never be larger than SQUASHFS_NAME_LEN */			if (size > SQUASHFS_NAME_LEN)				goto failed_read; 			err = squashfs_read_metadata(inode->i_sb, dire->name,					&block, &offset, size);			if (err < 0)				goto failed_read; 			length += sizeof(*dire) + size; 			if (ctx->pos >= length)				continue; 			dire->name[size] = '\0';			inode_number = le32_to_cpu(dirh.inode_number) +				((short) le16_to_cpu(dire->inode_number));			type = le16_to_cpu(dire->type); 			if (type > SQUASHFS_MAX_DIR_TYPE)				goto failed_read; 			if (!dir_emit(ctx, dire->name, size,					inode_number,					squashfs_filetype_table[type]))				goto finish; 			ctx->pos = length;		}	} finish:	kfree(dire);	return 0; failed_read:	ERROR("Unable to read directory block [%llx:%x]\n", block, offset);	kfree(dire);	return 0;}  const struct file_operations squashfs_dir_ops = {	.read = generic_read_dir,	.iterate_shared = squashfs_readdir,	.llseek = generic_file_llseek,	.setlease = generic_setlease,};