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