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179 lines
4.7 KiB
179 lines
4.7 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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* export.c |
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*/ |
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/* |
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* This file implements code to make Squashfs filesystems exportable (NFS etc.) |
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* |
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* The export code uses an inode lookup table to map inode numbers passed in |
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* filehandles to an inode location on disk. This table is stored compressed |
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* into metadata blocks. A second index table is used to locate these. This |
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* second index table for speed of access (and because it is small) is read at |
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* mount time and cached in memory. |
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* |
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* The inode lookup table is used only by the export code, inode disk |
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* locations are directly encoded in directories, enabling direct access |
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* without an intermediate lookup for all operations except the export ops. |
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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/dcache.h> |
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#include <linux/exportfs.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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/* |
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* Look-up inode number (ino) in table, returning the inode location. |
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*/ |
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static long long squashfs_inode_lookup(struct super_block *sb, int ino_num) |
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{ |
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struct squashfs_sb_info *msblk = sb->s_fs_info; |
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int blk = SQUASHFS_LOOKUP_BLOCK(ino_num - 1); |
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int offset = SQUASHFS_LOOKUP_BLOCK_OFFSET(ino_num - 1); |
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u64 start; |
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__le64 ino; |
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int err; |
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TRACE("Entered squashfs_inode_lookup, inode_number = %d\n", ino_num); |
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if (ino_num == 0 || (ino_num - 1) >= msblk->inodes) |
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return -EINVAL; |
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start = le64_to_cpu(msblk->inode_lookup_table[blk]); |
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err = squashfs_read_metadata(sb, &ino, &start, &offset, sizeof(ino)); |
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if (err < 0) |
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return err; |
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TRACE("squashfs_inode_lookup, inode = 0x%llx\n", |
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(u64) le64_to_cpu(ino)); |
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return le64_to_cpu(ino); |
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} |
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static struct dentry *squashfs_export_iget(struct super_block *sb, |
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unsigned int ino_num) |
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{ |
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long long ino; |
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struct dentry *dentry = ERR_PTR(-ENOENT); |
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TRACE("Entered squashfs_export_iget\n"); |
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ino = squashfs_inode_lookup(sb, ino_num); |
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if (ino >= 0) |
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dentry = d_obtain_alias(squashfs_iget(sb, ino, ino_num)); |
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return dentry; |
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} |
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static struct dentry *squashfs_fh_to_dentry(struct super_block *sb, |
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struct fid *fid, int fh_len, int fh_type) |
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{ |
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if ((fh_type != FILEID_INO32_GEN && fh_type != FILEID_INO32_GEN_PARENT) |
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|| fh_len < 2) |
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return NULL; |
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return squashfs_export_iget(sb, fid->i32.ino); |
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} |
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static struct dentry *squashfs_fh_to_parent(struct super_block *sb, |
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struct fid *fid, int fh_len, int fh_type) |
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{ |
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if (fh_type != FILEID_INO32_GEN_PARENT || fh_len < 4) |
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return NULL; |
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return squashfs_export_iget(sb, fid->i32.parent_ino); |
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} |
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static struct dentry *squashfs_get_parent(struct dentry *child) |
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{ |
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struct inode *inode = d_inode(child); |
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unsigned int parent_ino = squashfs_i(inode)->parent; |
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return squashfs_export_iget(inode->i_sb, parent_ino); |
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} |
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/* |
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* Read uncompressed inode lookup table indexes off disk into memory |
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*/ |
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__le64 *squashfs_read_inode_lookup_table(struct super_block *sb, |
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u64 lookup_table_start, u64 next_table, unsigned int inodes) |
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{ |
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unsigned int length = SQUASHFS_LOOKUP_BLOCK_BYTES(inodes); |
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unsigned int indexes = SQUASHFS_LOOKUP_BLOCKS(inodes); |
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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_inode_lookup_table, length %d\n", length); |
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/* Sanity check values */ |
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/* there should always be at least one inode */ |
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if (inodes == 0) |
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return ERR_PTR(-EINVAL); |
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/* |
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* The computed size of the lookup 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 - lookup_table_start)) |
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return ERR_PTR(-EINVAL); |
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table = squashfs_read_table(sb, lookup_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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* table0], table[1], ... table[indexes - 1] store the locations |
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* of the compressed inode lookup blocks. Each entry should be |
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* less than the next (i.e. table[0] < table[1]), and the difference |
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* between them should be SQUASHFS_METADATA_SIZE or less. |
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* table[indexes - 1] should be less than lookup_table_start, and |
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* again the difference 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 |
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|| (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 >= lookup_table_start || |
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(lookup_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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const struct export_operations squashfs_export_ops = { |
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.fh_to_dentry = squashfs_fh_to_dentry, |
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.fh_to_parent = squashfs_fh_to_parent, |
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.get_parent = squashfs_get_parent |
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};
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