// 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>
 *
 * super.c
 */

/*
 * This file implements code to read the superblock, read and initialise
 * in-memory structures at mount time, and all the VFS glue code to register
 * the filesystem.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/fs.h>
#include <linux/fs_context.h>
#include <linux/vfs.h>
#include <linux/slab.h>
#include <linux/mutex.h>
#include <linux/pagemap.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/magic.h>
#include <linux/xattr.h>

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

static struct file_system_type squashfs_fs_type;
static const struct super_operations squashfs_super_ops;

static const struct squashfs_decompressor *supported_squashfs_filesystem(
        struct fs_context *fc,
        short major, short minor, short id)
{
        const struct squashfs_decompressor *decompressor;

        if (major < SQUASHFS_MAJOR) {
                errorf(fc, "Major/Minor mismatch, older Squashfs %d.%d "
                       "filesystems are unsupported", major, minor);
                return NULL;
        } else if (major > SQUASHFS_MAJOR || minor > SQUASHFS_MINOR) {
                errorf(fc, "Major/Minor mismatch, trying to mount newer "
                       "%d.%d filesystem", major, minor);
                errorf(fc, "Please update your kernel");
                return NULL;
        }

        decompressor = squashfs_lookup_decompressor(id);
        if (!decompressor->supported) {
                errorf(fc, "Filesystem uses \"%s\" compression. This is not supported",
                       decompressor->name);
                return NULL;
        }

        return decompressor;
}


static int squashfs_fill_super(struct super_block *sb, struct fs_context *fc)
{
        struct squashfs_sb_info *msblk;
        struct squashfs_super_block *sblk = NULL;
        struct inode *root;
        long long root_inode;
        unsigned short flags;
        unsigned int fragments;
        u64 lookup_table_start, xattr_id_table_start, next_table;
        int err;

        TRACE("Entered squashfs_fill_superblock\n");

        sb->s_fs_info = kzalloc(sizeof(*msblk), GFP_KERNEL);
        if (sb->s_fs_info == NULL) {
                ERROR("Failed to allocate squashfs_sb_info\n");
                return -ENOMEM;
        }
        msblk = sb->s_fs_info;

        msblk->devblksize = sb_min_blocksize(sb, SQUASHFS_DEVBLK_SIZE);
        msblk->devblksize_log2 = ffz(~msblk->devblksize);

        mutex_init(&msblk->meta_index_mutex);

        /*
         * msblk->bytes_used is checked in squashfs_read_table to ensure reads
         * are not beyond filesystem end.  But as we're using
         * squashfs_read_table here to read the superblock (including the value
         * of bytes_used) we need to set it to an initial sensible dummy value
         */
        msblk->bytes_used = sizeof(*sblk);
        sblk = squashfs_read_table(sb, SQUASHFS_START, sizeof(*sblk));

        if (IS_ERR(sblk)) {
                errorf(fc, "unable to read squashfs_super_block");
                err = PTR_ERR(sblk);
                sblk = NULL;
                goto failed_mount;
        }

        err = -EINVAL;

        /* Check it is a SQUASHFS superblock */
        sb->s_magic = le32_to_cpu(sblk->s_magic);
        if (sb->s_magic != SQUASHFS_MAGIC) {
                if (!(fc->sb_flags & SB_SILENT))
                        errorf(fc, "Can't find a SQUASHFS superblock on %pg",
                               sb->s_bdev);
                goto failed_mount;
        }

        /* Check the MAJOR & MINOR versions and lookup compression type */
        msblk->decompressor = supported_squashfs_filesystem(
                        fc,
                        le16_to_cpu(sblk->s_major),
                        le16_to_cpu(sblk->s_minor),
                        le16_to_cpu(sblk->compression));
        if (msblk->decompressor == NULL)
                goto failed_mount;

        /* Check the filesystem does not extend beyond the end of the
           block device */
        msblk->bytes_used = le64_to_cpu(sblk->bytes_used);
        if (msblk->bytes_used < 0 || msblk->bytes_used >
                        i_size_read(sb->s_bdev->bd_inode))
                goto failed_mount;

        /* Check block size for sanity */
        msblk->block_size = le32_to_cpu(sblk->block_size);
        if (msblk->block_size > SQUASHFS_FILE_MAX_SIZE)
                goto insanity;

        /*
         * Check the system page size is not larger than the filesystem
         * block size (by default 128K).  This is currently not supported.
         */
        if (PAGE_SIZE > msblk->block_size) {
                errorf(fc, "Page size > filesystem block size (%d).  This is "
                       "currently not supported!", msblk->block_size);
                goto failed_mount;
        }

        /* Check block log for sanity */
        msblk->block_log = le16_to_cpu(sblk->block_log);
        if (msblk->block_log > SQUASHFS_FILE_MAX_LOG)
                goto failed_mount;

        /* Check that block_size and block_log match */
        if (msblk->block_size != (1 << msblk->block_log))
                goto insanity;

        /* Check the root inode for sanity */
        root_inode = le64_to_cpu(sblk->root_inode);
        if (SQUASHFS_INODE_OFFSET(root_inode) > SQUASHFS_METADATA_SIZE)
                goto insanity;

        msblk->inode_table = le64_to_cpu(sblk->inode_table_start);
        msblk->directory_table = le64_to_cpu(sblk->directory_table_start);
        msblk->inodes = le32_to_cpu(sblk->inodes);
        msblk->fragments = le32_to_cpu(sblk->fragments);
        msblk->ids = le16_to_cpu(sblk->no_ids);
        flags = le16_to_cpu(sblk->flags);

        TRACE("Found valid superblock on %pg\n", sb->s_bdev);
        TRACE("Inodes are %scompressed\n", SQUASHFS_UNCOMPRESSED_INODES(flags)
                                ? "un" : "");
        TRACE("Data is %scompressed\n", SQUASHFS_UNCOMPRESSED_DATA(flags)
                                ? "un" : "");
        TRACE("Filesystem size %lld bytes\n", msblk->bytes_used);
        TRACE("Block size %d\n", msblk->block_size);
        TRACE("Number of inodes %d\n", msblk->inodes);
        TRACE("Number of fragments %d\n", msblk->fragments);
        TRACE("Number of ids %d\n", msblk->ids);
        TRACE("sblk->inode_table_start %llx\n", msblk->inode_table);
        TRACE("sblk->directory_table_start %llx\n", msblk->directory_table);
        TRACE("sblk->fragment_table_start %llx\n",
                (u64) le64_to_cpu(sblk->fragment_table_start));
        TRACE("sblk->id_table_start %llx\n",
                (u64) le64_to_cpu(sblk->id_table_start));

        sb->s_maxbytes = MAX_LFS_FILESIZE;
        sb->s_time_min = 0;
        sb->s_time_max = U32_MAX;
        sb->s_flags |= SB_RDONLY;
        sb->s_op = &squashfs_super_ops;

        err = -ENOMEM;

        msblk->block_cache = squashfs_cache_init("metadata",
                        SQUASHFS_CACHED_BLKS, SQUASHFS_METADATA_SIZE);
        if (msblk->block_cache == NULL)
                goto failed_mount;

        /* Allocate read_page block */
        msblk->read_page = squashfs_cache_init("data",
                squashfs_max_decompressors(), msblk->block_size);
        if (msblk->read_page == NULL) {
                errorf(fc, "Failed to allocate read_page block");
                goto failed_mount;
        }

        msblk->stream = squashfs_decompressor_setup(sb, flags);
        if (IS_ERR(msblk->stream)) {
                err = PTR_ERR(msblk->stream);
                msblk->stream = NULL;
                goto insanity;
        }

        /* Handle xattrs */
        sb->s_xattr = squashfs_xattr_handlers;
        xattr_id_table_start = le64_to_cpu(sblk->xattr_id_table_start);
        if (xattr_id_table_start == SQUASHFS_INVALID_BLK) {
                next_table = msblk->bytes_used;
                goto allocate_id_index_table;
        }

        /* Allocate and read xattr id lookup table */
        msblk->xattr_id_table = squashfs_read_xattr_id_table(sb,
                xattr_id_table_start, &msblk->xattr_table, &msblk->xattr_ids);
        if (IS_ERR(msblk->xattr_id_table)) {
                errorf(fc, "unable to read xattr id index table");
                err = PTR_ERR(msblk->xattr_id_table);
                msblk->xattr_id_table = NULL;
                if (err != -ENOTSUPP)
                        goto failed_mount;
        }
        next_table = msblk->xattr_table;

allocate_id_index_table:
        /* Allocate and read id index table */
        msblk->id_table = squashfs_read_id_index_table(sb,
                le64_to_cpu(sblk->id_table_start), next_table, msblk->ids);
        if (IS_ERR(msblk->id_table)) {
                errorf(fc, "unable to read id index table");
                err = PTR_ERR(msblk->id_table);
                msblk->id_table = NULL;
                goto failed_mount;
        }
        next_table = le64_to_cpu(msblk->id_table[0]);

        /* Handle inode lookup table */
        lookup_table_start = le64_to_cpu(sblk->lookup_table_start);
        if (lookup_table_start == SQUASHFS_INVALID_BLK)
                goto handle_fragments;

        /* Allocate and read inode lookup table */
        msblk->inode_lookup_table = squashfs_read_inode_lookup_table(sb,
                lookup_table_start, next_table, msblk->inodes);
        if (IS_ERR(msblk->inode_lookup_table)) {
                errorf(fc, "unable to read inode lookup table");
                err = PTR_ERR(msblk->inode_lookup_table);
                msblk->inode_lookup_table = NULL;
                goto failed_mount;
        }
        next_table = le64_to_cpu(msblk->inode_lookup_table[0]);

        sb->s_export_op = &squashfs_export_ops;

handle_fragments:
        fragments = msblk->fragments;
        if (fragments == 0)
                goto check_directory_table;

        msblk->fragment_cache = squashfs_cache_init("fragment",
                SQUASHFS_CACHED_FRAGMENTS, msblk->block_size);
        if (msblk->fragment_cache == NULL) {
                err = -ENOMEM;
                goto failed_mount;
        }

        /* Allocate and read fragment index table */
        msblk->fragment_index = squashfs_read_fragment_index_table(sb,
                le64_to_cpu(sblk->fragment_table_start), next_table, fragments);
        if (IS_ERR(msblk->fragment_index)) {
                errorf(fc, "unable to read fragment index table");
                err = PTR_ERR(msblk->fragment_index);
                msblk->fragment_index = NULL;
                goto failed_mount;
        }
        next_table = le64_to_cpu(msblk->fragment_index[0]);

check_directory_table:
        /* Sanity check directory_table */
        if (msblk->directory_table > next_table) {
                err = -EINVAL;
                goto insanity;
        }

        /* Sanity check inode_table */
        if (msblk->inode_table >= msblk->directory_table) {
                err = -EINVAL;
                goto insanity;
        }

        /* allocate root */
        root = new_inode(sb);
        if (!root) {
                err = -ENOMEM;
                goto failed_mount;
        }

        err = squashfs_read_inode(root, root_inode);
        if (err) {
                make_bad_inode(root);
                iput(root);
                goto failed_mount;
        }
        insert_inode_hash(root);

        sb->s_root = d_make_root(root);
        if (sb->s_root == NULL) {
                ERROR("Root inode create failed\n");
                err = -ENOMEM;
                goto failed_mount;
        }

        TRACE("Leaving squashfs_fill_super\n");
        kfree(sblk);
        return 0;

insanity:
        errorf(fc, "squashfs image failed sanity check");
failed_mount:
        squashfs_cache_delete(msblk->block_cache);
        squashfs_cache_delete(msblk->fragment_cache);
        squashfs_cache_delete(msblk->read_page);
        squashfs_decompressor_destroy(msblk);
        kfree(msblk->inode_lookup_table);
        kfree(msblk->fragment_index);
        kfree(msblk->id_table);
        kfree(msblk->xattr_id_table);
        kfree(sb->s_fs_info);
        sb->s_fs_info = NULL;
        kfree(sblk);
        return err;
}

static int squashfs_get_tree(struct fs_context *fc)
{
        return get_tree_bdev(fc, squashfs_fill_super);
}

static int squashfs_reconfigure(struct fs_context *fc)
{
        sync_filesystem(fc->root->d_sb);
        fc->sb_flags |= SB_RDONLY;
        return 0;
}

static const struct fs_context_operations squashfs_context_ops = {
        .get_tree       = squashfs_get_tree,
        .reconfigure    = squashfs_reconfigure,
};

static int squashfs_init_fs_context(struct fs_context *fc)
{
        fc->ops = &squashfs_context_ops;
        return 0;
}

static int squashfs_statfs(struct dentry *dentry, struct kstatfs *buf)
{
        struct squashfs_sb_info *msblk = dentry->d_sb->s_fs_info;
        u64 id = huge_encode_dev(dentry->d_sb->s_bdev->bd_dev);

        TRACE("Entered squashfs_statfs\n");

        buf->f_type = SQUASHFS_MAGIC;
        buf->f_bsize = msblk->block_size;
        buf->f_blocks = ((msblk->bytes_used - 1) >> msblk->block_log) + 1;
        buf->f_bfree = buf->f_bavail = 0;
        buf->f_files = msblk->inodes;
        buf->f_ffree = 0;
        buf->f_namelen = SQUASHFS_NAME_LEN;
        buf->f_fsid = u64_to_fsid(id);

        return 0;
}


static void squashfs_put_super(struct super_block *sb)
{
        if (sb->s_fs_info) {
                struct squashfs_sb_info *sbi = sb->s_fs_info;
                squashfs_cache_delete(sbi->block_cache);
                squashfs_cache_delete(sbi->fragment_cache);
                squashfs_cache_delete(sbi->read_page);
                squashfs_decompressor_destroy(sbi);
                kfree(sbi->id_table);
                kfree(sbi->fragment_index);
                kfree(sbi->meta_index);
                kfree(sbi->inode_lookup_table);
                kfree(sbi->xattr_id_table);
                kfree(sb->s_fs_info);
                sb->s_fs_info = NULL;
        }
}

static struct kmem_cache *squashfs_inode_cachep;


static void init_once(void *foo)
{
        struct squashfs_inode_info *ei = foo;

        inode_init_once(&ei->vfs_inode);
}


static int __init init_inodecache(void)
{
        squashfs_inode_cachep = kmem_cache_create("squashfs_inode_cache",
                sizeof(struct squashfs_inode_info), 0,
                SLAB_HWCACHE_ALIGN|SLAB_RECLAIM_ACCOUNT|SLAB_ACCOUNT,
                init_once);

        return squashfs_inode_cachep ? 0 : -ENOMEM;
}


static void destroy_inodecache(void)
{
        /*
         * Make sure all delayed rcu free inodes are flushed before we
         * destroy cache.
         */
        rcu_barrier();
        kmem_cache_destroy(squashfs_inode_cachep);
}


static int __init init_squashfs_fs(void)
{
        int err = init_inodecache();

        if (err)
                return err;

        err = register_filesystem(&squashfs_fs_type);
        if (err) {
                destroy_inodecache();
                return err;
        }

        pr_info("version 4.0 (2009/01/31) Phillip Lougher\n");

        return 0;
}


static void __exit exit_squashfs_fs(void)
{
        unregister_filesystem(&squashfs_fs_type);
        destroy_inodecache();
}


static struct inode *squashfs_alloc_inode(struct super_block *sb)
{
        struct squashfs_inode_info *ei =
                kmem_cache_alloc(squashfs_inode_cachep, GFP_KERNEL);

        return ei ? &ei->vfs_inode : NULL;
}


static void squashfs_free_inode(struct inode *inode)
{
        kmem_cache_free(squashfs_inode_cachep, squashfs_i(inode));
}

static struct file_system_type squashfs_fs_type = {
        .owner = THIS_MODULE,
        .name = "squashfs",
        .init_fs_context = squashfs_init_fs_context,
        .kill_sb = kill_block_super,
        .fs_flags = FS_REQUIRES_DEV
};
MODULE_ALIAS_FS("squashfs");

static const struct super_operations squashfs_super_ops = {
        .alloc_inode = squashfs_alloc_inode,
        .free_inode = squashfs_free_inode,
        .statfs = squashfs_statfs,
        .put_super = squashfs_put_super,
};

module_init(init_squashfs_fs);
module_exit(exit_squashfs_fs);
MODULE_DESCRIPTION("squashfs 4.0, a compressed read-only filesystem");
MODULE_AUTHOR("Phillip Lougher <phillip@squashfs.org.uk>");
MODULE_LICENSE("GPL");