fs/squashfs/namei.c - linux - Git at Google

 // 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>
  *
  * namei.c
  */

 /*
  * This file implements code to do filename lookup in directories.
  *
  * Like inodes, directories are packed into compressed metadata blocks, stored
  * in a directory table.  Directories are accessed using the start address of
  * the metablock containing the directory and the offset into the
  * decompressed block (<block, offset>).
  *
  * Directories are organised in a slightly complex way, and are not simply
  * a list of file names.  The organisation takes advantage of the
  * fact that (in most cases) the inodes of the files will be in the same
  * compressed metadata block, and therefore, can share the start block.
  * Directories are therefore organised in a two level list, a directory
  * header containing the shared start block value, and a sequence of directory
  * entries, each of which share the shared start block.  A new directory header
  * is written once/if the inode start block changes.  The directory
  * header/directory entry list is repeated as many times as necessary.
  *
  * Directories are sorted, and can contain a directory index to speed up
  * file lookup.  Directory indexes store one entry per metablock, each entry
  * storing the index/filename mapping to the first directory header
  * in each metadata block.  Directories are sorted in alphabetical order,
  * and at lookup the index is scanned linearly looking for the first filename
  * alphabetically larger than the filename being looked up.  At this point the
  * location of the metadata block the filename is in has been found.
  * The general idea of the index is ensure only one metadata block needs to be
  * decompressed to do a lookup irrespective of the length of the directory.
  * This scheme has the advantage that it doesn't require extra memory overhead
  * and doesn't require much extra storage on disk.
  */

 #include <linux/fs.h>
 #include <linux/vfs.h>
 #include <linux/slab.h>
 #include <linux/string.h>
 #include <linux/dcache.h>
 #include <linux/xattr.h>

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

 /*
  * Lookup name in the directory index, returning the location of the metadata
  * block containing it, and the directory index this represents.
  *
  * 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_name(struct super_block *sb,
 			u64 *next_block, int *next_offset, u64 index_start,
 			int index_offset, int i_count, const char *name,
 			int len)
 {
 	struct squashfs_sb_info *msblk = sb->s_fs_info;
 	int i, length = 0, err;
 	unsigned int size;
 	struct squashfs_dir_index *index;
 	char *str;

 	TRACE("Entered get_dir_index_using_name, i_count %d\n", i_count);

 	index = kmalloc(sizeof(*index) + SQUASHFS_NAME_LEN * 2 + 2, GFP_KERNEL);
 	if (index == NULL) {
 		ERROR("Failed to allocate squashfs_dir_index\n");
 		goto out;
 	}

 	str = &index->name[SQUASHFS_NAME_LEN + 1];
 	strncpy(str, name, len);
 	str[len] = '\0';

 	for (i = 0; i < i_count; i++) {
 		err = squashfs_read_metadata(sb, index, &index_start,
 					&index_offset, sizeof(*index));
 		if (err < 0)
 			break;


 		size = le32_to_cpu(index->size) + 1;
 		if (size > SQUASHFS_NAME_LEN)
 			break;

 		err = squashfs_read_metadata(sb, index->name, &index_start,
 					&index_offset, size);
 		if (err < 0)
 			break;

 		index->name[size] = '\0';

 		if (strcmp(index->name, str) > 0)
 			break;

 		length = le32_to_cpu(index->index);
 		*next_block = le32_to_cpu(index->start_block) +
 					msblk->directory_table;
 	}

 	*next_offset = (length + *next_offset) % SQUASHFS_METADATA_SIZE;
 	kfree(index);

 out:
 	/*
 	 * Return index (f_pos) of the looked up metadata block.  Translate
 	 * from internal f_pos to external f_pos which is offset by 3 because
 	 * we invent "." and ".." entries which are not actually stored in the
 	 * directory.
 	 */
 	return length + 3;
 }


 static struct dentry *squashfs_lookup(struct inode *dir, struct dentry *dentry,
 				 unsigned int flags)
 {
 	const unsigned char *name = dentry->d_name.name;
 	int len = dentry->d_name.len;
 	struct inode *inode = NULL;
 	struct squashfs_sb_info *msblk = dir->i_sb->s_fs_info;
 	struct squashfs_dir_header dirh;
 	struct squashfs_dir_entry *dire;
 	u64 block = squashfs_i(dir)->start + msblk->directory_table;
 	int offset = squashfs_i(dir)->offset;
 	int err, length;
 	unsigned int dir_count, size;

 	TRACE("Entered squashfs_lookup [%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");
 		return ERR_PTR(-ENOMEM);
 	}

 	if (len > SQUASHFS_NAME_LEN) {
 		err = -ENAMETOOLONG;
 		goto failed;
 	}

 	length = get_dir_index_using_name(dir->i_sb, &block, &offset,
 				squashfs_i(dir)->dir_idx_start,
 				squashfs_i(dir)->dir_idx_offset,
 				squashfs_i(dir)->dir_idx_cnt, name, len);

 	while (length < i_size_read(dir)) {
 		/*
 		 * Read directory header.
 		 */
 		err = squashfs_read_metadata(dir->i_sb, &dirh, &block,
 				&offset, sizeof(dirh));
 		if (err < 0)
 			goto read_failure;

 		length += sizeof(dirh);

 		dir_count = le32_to_cpu(dirh.count) + 1;

 		if (dir_count > SQUASHFS_DIR_COUNT)
 			goto data_error;

 		while (dir_count--) {
 			/*
 			 * Read directory entry.
 			 */
 			err = squashfs_read_metadata(dir->i_sb, dire, &block,
 					&offset, sizeof(*dire));
 			if (err < 0)
 				goto read_failure;

 			size = le16_to_cpu(dire->size) + 1;

 			/* size should never be larger than SQUASHFS_NAME_LEN */
 			if (size > SQUASHFS_NAME_LEN)
 				goto data_error;

 			err = squashfs_read_metadata(dir->i_sb, dire->name,
 					&block, &offset, size);
 			if (err < 0)
 				goto read_failure;

 			length += sizeof(*dire) + size;

 			if (name[0] < dire->name[0])
 				goto exit_lookup;

 			if (len == size && !strncmp(name, dire->name, len)) {
 				unsigned int blk, off, ino_num;
 				long long ino;
 				blk = le32_to_cpu(dirh.start_block);
 				off = le16_to_cpu(dire->offset);
 				ino_num = le32_to_cpu(dirh.inode_number) +
 					(short) le16_to_cpu(dire->inode_number);
 				ino = SQUASHFS_MKINODE(blk, off);

 				TRACE("calling squashfs_iget for directory "
 					"entry %s, inode  %x:%x, %d\n", name,
 					blk, off, ino_num);

 				inode = squashfs_iget(dir->i_sb, ino, ino_num);
 				goto exit_lookup;
 			}
 		}
 	}

 exit_lookup:
 	kfree(dire);
 	return d_splice_alias(inode, dentry);

 data_error:
 	err = -EIO;

 read_failure:
 	ERROR("Unable to read directory block [%llx:%x]\n",
 		squashfs_i(dir)->start + msblk->directory_table,
 		squashfs_i(dir)->offset);
 failed:
 	kfree(dire);
 	return ERR_PTR(err);
 }


 const struct inode_operations squashfs_dir_inode_ops = {
 	.lookup = squashfs_lookup,
 	.listxattr = squashfs_listxattr
 };
	// 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>
	*
	* namei.c
	*/

	/*
	* This file implements code to do filename lookup in directories.
	*
	* Like inodes, directories are packed into compressed metadata blocks, stored
	* in a directory table. Directories are accessed using the start address of
	* the metablock containing the directory and the offset into the
	* decompressed block (<block, offset>).
	*
	* Directories are organised in a slightly complex way, and are not simply
	* a list of file names. The organisation takes advantage of the
	* fact that (in most cases) the inodes of the files will be in the same
	* compressed metadata block, and therefore, can share the start block.
	* Directories are therefore organised in a two level list, a directory
	* header containing the shared start block value, and a sequence of directory
	* entries, each of which share the shared start block. A new directory header
	* is written once/if the inode start block changes. The directory
	* header/directory entry list is repeated as many times as necessary.
	*
	* Directories are sorted, and can contain a directory index to speed up
	* file lookup. Directory indexes store one entry per metablock, each entry
	* storing the index/filename mapping to the first directory header
	* in each metadata block. Directories are sorted in alphabetical order,
	* and at lookup the index is scanned linearly looking for the first filename
	* alphabetically larger than the filename being looked up. At this point the
	* location of the metadata block the filename is in has been found.
	* The general idea of the index is ensure only one metadata block needs to be
	* decompressed to do a lookup irrespective of the length of the directory.
	* This scheme has the advantage that it doesn't require extra memory overhead
	* and doesn't require much extra storage on disk.
	*/

	#include <linux/fs.h>
	#include <linux/vfs.h>
	#include <linux/slab.h>
	#include <linux/string.h>
	#include <linux/dcache.h>
	#include <linux/xattr.h>

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

	/*
	* Lookup name in the directory index, returning the location of the metadata
	* block containing it, and the directory index this represents.
	*
	* 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_name(struct super_block *sb,
	u64 next_block, int next_offset, u64 index_start,
	int index_offset, int i_count, const char *name,
	int len)
	{
	struct squashfs_sb_info *msblk = sb->s_fs_info;
	int i, length = 0, err;
	unsigned int size;
	struct squashfs_dir_index *index;
	char *str;

	TRACE("Entered get_dir_index_using_name, i_count %d\n", i_count);

	index = kmalloc(sizeof(index) + SQUASHFS_NAME_LEN 2 + 2, GFP_KERNEL);
	if (index == NULL) {
	ERROR("Failed to allocate squashfs_dir_index\n");
	goto out;
	}

	str = &index->name[SQUASHFS_NAME_LEN + 1];
	strncpy(str, name, len);
	str[len] = '\0';

	for (i = 0; i < i_count; i++) {
	err = squashfs_read_metadata(sb, index, &index_start,
	&index_offset, sizeof(*index));
	if (err < 0)
	break;


	size = le32_to_cpu(index->size) + 1;
	if (size > SQUASHFS_NAME_LEN)
	break;

	err = squashfs_read_metadata(sb, index->name, &index_start,
	&index_offset, size);
	if (err < 0)
	break;

	index->name[size] = '\0';

	if (strcmp(index->name, str) > 0)
	break;

	length = le32_to_cpu(index->index);
	*next_block = le32_to_cpu(index->start_block) +
	msblk->directory_table;
	}

	next_offset = (length + next_offset) % SQUASHFS_METADATA_SIZE;
	kfree(index);

	out:
	/*
	* Return index (f_pos) of the looked up metadata block. Translate
	* from internal f_pos to external f_pos which is offset by 3 because
	* we invent "." and ".." entries which are not actually stored in the
	* directory.
	*/
	return length + 3;
	}


	static struct dentry squashfs_lookup(struct inode dir, struct dentry *dentry,
	unsigned int flags)
	{
	const unsigned char *name = dentry->d_name.name;
	int len = dentry->d_name.len;
	struct inode *inode = NULL;
	struct squashfs_sb_info *msblk = dir->i_sb->s_fs_info;
	struct squashfs_dir_header dirh;
	struct squashfs_dir_entry *dire;
	u64 block = squashfs_i(dir)->start + msblk->directory_table;
	int offset = squashfs_i(dir)->offset;
	int err, length;
	unsigned int dir_count, size;

	TRACE("Entered squashfs_lookup [%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");
	return ERR_PTR(-ENOMEM);
	}

	if (len > SQUASHFS_NAME_LEN) {
	err = -ENAMETOOLONG;
	goto failed;
	}

	length = get_dir_index_using_name(dir->i_sb, &block, &offset,
	squashfs_i(dir)->dir_idx_start,
	squashfs_i(dir)->dir_idx_offset,
	squashfs_i(dir)->dir_idx_cnt, name, len);

	while (length < i_size_read(dir)) {
	/*
	* Read directory header.
	*/
	err = squashfs_read_metadata(dir->i_sb, &dirh, &block,
	&offset, sizeof(dirh));
	if (err < 0)
	goto read_failure;

	length += sizeof(dirh);

	dir_count = le32_to_cpu(dirh.count) + 1;

	if (dir_count > SQUASHFS_DIR_COUNT)
	goto data_error;

	while (dir_count--) {
	/*
	* Read directory entry.
	*/
	err = squashfs_read_metadata(dir->i_sb, dire, &block,
	&offset, sizeof(*dire));
	if (err < 0)
	goto read_failure;

	size = le16_to_cpu(dire->size) + 1;

	/* size should never be larger than SQUASHFS_NAME_LEN */
	if (size > SQUASHFS_NAME_LEN)
	goto data_error;

	err = squashfs_read_metadata(dir->i_sb, dire->name,
	&block, &offset, size);
	if (err < 0)
	goto read_failure;

	length += sizeof(*dire) + size;

	if (name[0] < dire->name[0])
	goto exit_lookup;

	if (len == size && !strncmp(name, dire->name, len)) {
	unsigned int blk, off, ino_num;
	long long ino;
	blk = le32_to_cpu(dirh.start_block);
	off = le16_to_cpu(dire->offset);
	ino_num = le32_to_cpu(dirh.inode_number) +
	(short) le16_to_cpu(dire->inode_number);
	ino = SQUASHFS_MKINODE(blk, off);

	TRACE("calling squashfs_iget for directory "
	"entry %s, inode %x:%x, %d\n", name,
	blk, off, ino_num);

	inode = squashfs_iget(dir->i_sb, ino, ino_num);
	goto exit_lookup;
	}
	}
	}

	exit_lookup:
	kfree(dire);
	return d_splice_alias(inode, dentry);

	data_error:
	err = -EIO;

	read_failure:
	ERROR("Unable to read directory block [%llx:%x]\n",
	squashfs_i(dir)->start + msblk->directory_table,
	squashfs_i(dir)->offset);
	failed:
	kfree(dire);
	return ERR_PTR(err);
	}


	const struct inode_operations squashfs_dir_inode_ops = {
	.lookup = squashfs_lookup,
	.listxattr = squashfs_listxattr
	};