2
This commit is contained in:
parent
42839e6cd9
commit
f468260cb1
326
libfs.c
326
libfs.c
@ -1,27 +1,27 @@
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#include <linux/init.h>
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#include <linux/module.h>
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#include <linux/fs.h>
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#include <linux/init.h>
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#include <linux/pagemap.h>
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#include <linux/mount.h>
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#include <linux/namei.h>
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#include <linux/mount.h>
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#include <linux/dcache.h>
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#include <linux/slab.h>
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#include <linux/uaccess.h>
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#include <linux/kernel.h>
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#include <linux/hashtable.h>
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#include <linux/fs_context.h>
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#include <linux/statfs.h>
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#include <linux/version.h>
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#define FS_NAME "customfs"
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#define FS_MAGIC 0x20240615
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#define BOOKS_MODE 01777
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#define AUTHORS_MODE 0777
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#define AUTHOR_SUBDIR_MODE 01777
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#define MODE_BOOKS 01777
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#define MODE_AUTHORS 0777
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#define MODE_AUTHOR_SUBDIR 01777
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("user");
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MODULE_DESCRIPTION("Custom FS with books and authors directories");
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MODULE_AUTHOR("you");
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MODULE_DESCRIPTION("Custom FS with books/authors behavior");
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static struct super_block *global_sb;
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static struct inode *books_inode;
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static struct inode *authors_inode;
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DEFINE_HASHTABLE(link_table, 6);
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struct link_entry {
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struct hlist_node node;
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@ -29,109 +29,31 @@ struct link_entry {
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struct inode *target;
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};
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DEFINE_HASHTABLE(link_table, 6);
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static void remove_links_to_inode(struct inode *inode) {
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struct link_entry *entry;
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struct hlist_node *tmp;
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int bkt;
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hash_for_each_safe(link_table, bkt, tmp, entry, node) {
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if (entry->target == inode) {
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printk(KERN_INFO "customfs: removing hardlink to inode %lu\n", inode->i_ino);
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d_delete(entry->link);
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hash_del(&entry->node);
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kfree(entry);
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}
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}
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}
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static void fs_evict_inode(struct inode *inode) {
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if (inode->i_sb && inode->i_sb->s_magic == FS_MAGIC) {
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if (S_ISREG(inode->i_mode)) {
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remove_links_to_inode(inode);
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}
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}
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truncate_inode_pages_final(&inode->i_data);
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clear_inode(inode);
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}
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static int fs_statfs(struct dentry *dentry, struct kstatfs *buf) {
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buf->f_type = FS_MAGIC;
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static ssize_t dummy_read(struct file *file, char __user *buf, size_t len, loff_t *ppos) {
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return 0;
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}
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static const struct super_operations fs_ops = {
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.evict_inode = fs_evict_inode,
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.statfs = fs_statfs,
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};
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static ssize_t books_file_read(struct file *file, char __user *buf, size_t len, loff_t *ppos) {
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return simple_read_from_buffer(buf, len, ppos, file->private_data, PAGE_SIZE);
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static ssize_t dummy_write(struct file *file, const char __user *buf, size_t len, loff_t *ppos) {
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return len;
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}
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static ssize_t books_file_write(struct file *file, const char __user *buf, size_t len, loff_t *ppos) {
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return simple_write_to_buffer(file->private_data, PAGE_SIZE, ppos, buf, len);
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}
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static const struct file_operations books_file_fops = {
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.read = books_file_read,
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.write = books_file_write,
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.llseek = generic_file_llseek,
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static const struct file_operations custom_file_ops = {
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.read = dummy_read,
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.write = dummy_write,
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.llseek = noop_llseek,
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};
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static const struct inode_operations books_file_iops = {
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.getattr = simple_getattr,
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.setattr = simple_setattr,
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};
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static const struct inode_operations author_subdir_iops;
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static int author_mkdir(struct user_namespace *ns, struct inode *dir, struct dentry *dentry, umode_t mode) {
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struct inode *inode = new_inode(dir->i_sb);
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if (!inode)
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return -ENOMEM;
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inode->i_ino = get_next_ino();
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inode_init_owner(&init_user_ns, inode, dir, S_IFDIR | AUTHOR_SUBDIR_MODE);
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inode->i_op = &author_subdir_iops;
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inode->i_fop = &simple_dir_operations;
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inc_nlink(inode);
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inc_nlink(dir);
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d_add(dentry, inode);
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printk(KERN_INFO "customfs: created author subdir '%s'\n", dentry->d_name.name);
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return 0;
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static bool is_protected_dentry(struct dentry *d) {
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return strcmp(d->d_name.name, "books") == 0 || strcmp(d->d_name.name, "authors") == 0;
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}
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static int author_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_dentry) {
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int err;
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struct inode *inode = d_inode(old_dentry);
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if (!S_ISREG(inode->i_mode)) return -EPERM;
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err = simple_link(old_dentry, dir, new_dentry);
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if (err == 0) {
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struct link_entry *entry = kmalloc(sizeof(*entry), GFP_KERNEL);
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if (entry) {
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entry->link = dget(new_dentry);
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entry->target = inode;
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hash_add(link_table, &entry->node, inode->i_ino);
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printk(KERN_INFO "customfs: created hardlink '%s' to inode %lu\n",
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new_dentry->d_name.name, inode->i_ino);
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}
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}
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return err;
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}
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static const struct inode_operations author_subdir_iops = {
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.lookup = simple_lookup,
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.mkdir = author_mkdir,
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.rmdir = simple_rmdir,
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.link = author_link,
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};
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static struct inode *fs_make_inode(struct super_block *sb, umode_t mode) {
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static struct inode *get_inode(struct super_block *sb, umode_t mode) {
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struct inode *inode = new_inode(sb);
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if (!inode)
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return NULL;
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inode->i_ino = get_next_ino();
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inode_init_owner(&init_user_ns, inode, NULL, mode);
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inode->i_ino = get_next_ino();
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inode->i_sb = sb;
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inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
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@ -140,100 +62,178 @@ static struct inode *fs_make_inode(struct super_block *sb, umode_t mode) {
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inode->i_fop = &simple_dir_operations;
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inc_nlink(inode);
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} else if (S_ISREG(mode)) {
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inode->i_fop = &books_file_fops;
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inode->i_op = &books_file_iops;
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inode->i_private = kzalloc(PAGE_SIZE, GFP_KERNEL);
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inode->i_fop = &custom_file_ops;
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}
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return inode;
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}
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static int fs_fill_super(struct super_block *sb, void *data, int silent) {
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struct inode *root_inode;
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struct dentry *root_dentry;
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struct dentry *books_dentry;
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struct dentry *authors_dentry;
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static int books_create(struct user_namespace *ns, struct inode *dir,
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struct dentry *dentry, umode_t mode, bool excl) {
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struct inode *inode = get_inode(dir->i_sb, S_IFREG | mode);
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if (!inode)
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return -ENOMEM;
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sb->s_magic = FS_MAGIC;
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sb->s_op = &fs_ops;
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inode->i_uid = current_fsuid();
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d_add(dentry, inode);
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return 0;
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}
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root_inode = fs_make_inode(sb, S_IFDIR | 0755);
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static const struct inode_operations books_dir_iops = {
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.lookup = simple_lookup,
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.create = books_create,
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};
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static void remove_links_to_inode(struct inode *inode) {
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int bkt;
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struct link_entry *entry;
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struct hlist_node *tmp;
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hash_for_each_safe(link_table, bkt, tmp, entry, node) {
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if (entry->target == inode) {
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d_delete(entry->link);
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dput(entry->link);
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hash_del(&entry->node);
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kfree(entry);
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printk(KERN_INFO "customfs: removed link to inode %lu\n", inode->i_ino);
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}
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}
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}
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static int custom_mkdir(struct user_namespace *ns, struct inode *dir, struct dentry *dentry, umode_t mode) {
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if (dir == global_sb->s_root->d_inode)
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return -EPERM;
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if (S_ISDIR(dir->i_mode)) {
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umode_t mode_only = dir->i_mode & 07777;
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if ((mode_only == MODE_AUTHORS || mode_only == MODE_AUTHOR_SUBDIR) &&
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!uid_eq(current_fsuid(), dir->i_uid))
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return -EACCES;
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}
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struct inode *inode = get_inode(dir->i_sb, S_IFDIR | MODE_AUTHOR_SUBDIR);
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if (!inode)
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return -ENOMEM;
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inode->i_uid = current_fsuid();
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d_add(dentry, inode);
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inc_nlink(dir);
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return 0;
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}
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static int custom_unlink(struct inode *dir, struct dentry *dentry) {
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if (dir == global_sb->s_root->d_inode && is_protected_dentry(dentry))
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return -EPERM;
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return simple_unlink(dir, dentry);
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}
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static int custom_rmdir(struct inode *dir, struct dentry *dentry) {
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if (dir == global_sb->s_root->d_inode && is_protected_dentry(dentry))
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return -EPERM;
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return simple_rmdir(dir, dentry);
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}
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static int custom_rename(struct user_namespace *ns,
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struct inode *old_dir, struct dentry *old_dentry,
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struct inode *new_dir, struct dentry *new_dentry,
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unsigned int flags) {
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if ((old_dir == global_sb->s_root->d_inode || new_dir == global_sb->s_root->d_inode) &&
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(is_protected_dentry(old_dentry) || is_protected_dentry(new_dentry)))
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return -EPERM;
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return simple_rename(ns, old_dir, old_dentry, new_dir, new_dentry, flags);
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}
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static int custom_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_dentry) {
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if (dir->i_sb != old_dentry->d_inode->i_sb)
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return -EXDEV;
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if (!S_ISREG(old_dentry->d_inode->i_mode))
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return -EPERM;
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int r = simple_link(old_dentry, dir, new_dentry);
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if (r == 0) {
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struct link_entry *e = kmalloc(sizeof(*e), GFP_KERNEL);
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if (!e)
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return -ENOMEM;
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e->target = d_inode(old_dentry);
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e->link = dget(new_dentry);
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hash_add(link_table, &e->node, e->target->i_ino);
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}
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return r;
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}
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static const struct inode_operations fs_dir_iops = {
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.lookup = simple_lookup,
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.mkdir = custom_mkdir,
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.unlink = custom_unlink,
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.rmdir = custom_rmdir,
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.rename = custom_rename,
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.link = custom_link,
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};
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static void evict_inode(struct inode *inode) {
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if (inode->i_sb == global_sb && inode->i_ino && S_ISREG(inode->i_mode))
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remove_links_to_inode(inode);
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clear_inode(inode);
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}
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static const struct super_operations fs_sops = {
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.statfs = simple_statfs,
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.drop_inode = generic_delete_inode,
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.evict_inode = evict_inode,
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};
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static int fill_super(struct super_block *sb, void *data, int silent) {
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struct inode *root_inode = get_inode(sb, S_IFDIR | 0755);
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if (!root_inode)
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return -ENOMEM;
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root_dentry = d_make_root(root_inode);
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struct dentry *root_dentry = d_make_root(root_inode);
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if (!root_dentry)
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return -ENOMEM;
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books_inode = fs_make_inode(sb, S_IFDIR | BOOKS_MODE);
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if (!books_inode)
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goto out_root;
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books_inode->i_op = &simple_dir_inode_operations;
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books_inode->i_fop = &simple_dir_operations;
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inc_nlink(books_inode);
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books_dentry = d_alloc_name(root_dentry, "books");
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if (!books_dentry)
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goto out_books;
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d_add(books_dentry, books_inode);
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d_rehash(books_dentry);
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printk(KERN_INFO "customfs: 'books' directory created\n");
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authors_inode = fs_make_inode(sb, S_IFDIR | AUTHORS_MODE);
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if (!authors_inode)
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goto out_books_dentry;
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authors_inode->i_op = &author_subdir_iops;
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inc_nlink(authors_inode);
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authors_dentry = d_alloc_name(root_dentry, "authors");
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if (!authors_dentry)
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goto out_authors;
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d_add(authors_dentry, authors_inode);
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d_rehash(authors_dentry);
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printk(KERN_INFO "customfs: 'authors' directory created\n");
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sb->s_root = root_dentry;
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sb->s_magic = FS_MAGIC;
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sb->s_op = &fs_sops;
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global_sb = sb;
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printk(KERN_INFO "customfs: fill_super completed\n");
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printk(KERN_INFO "customfs: root inode=%lu\n", root_inode->i_ino);
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printk(KERN_INFO "customfs: books inode=%lu\n", books_inode->i_ino);
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printk(KERN_INFO "customfs: authors inode=%lu\n", authors_inode->i_ino);
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// books
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books_inode = get_inode(sb, S_IFDIR | MODE_BOOKS);
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if (!books_inode)
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return -ENOMEM;
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books_inode->i_op = &books_dir_iops;
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books_inode->i_fop = &simple_dir_operations;
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struct dentry *books = d_alloc_name(root_dentry, "books");
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d_add(books, books_inode);
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// authors
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struct inode *authors_inode = get_inode(sb, S_IFDIR | MODE_AUTHORS);
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if (!authors_inode)
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return -ENOMEM;
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authors_inode->i_op = &fs_dir_iops;
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authors_inode->i_fop = &simple_dir_operations;
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struct dentry *authors = d_alloc_name(root_dentry, "authors");
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d_add(authors, authors_inode);
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return 0;
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out_authors:
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iput(authors_inode);
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out_books_dentry:
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dput(books_dentry);
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out_books:
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iput(books_inode);
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out_root:
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dput(root_dentry);
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iput(root_inode);
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return -ENOMEM;
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}
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static struct dentry *fs_mount(struct file_system_type *type, int flags,
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const char *dev, void *data) {
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printk(KERN_INFO "customfs: mounting\n");
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return mount_nodev(type, flags, data, fs_fill_super);
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static struct dentry *mount_fs(struct file_system_type *type, int flags, const char *dev, void *data) {
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return mount_nodev(type, flags, data, fill_super);
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}
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static struct file_system_type fs_type = {
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.owner = THIS_MODULE,
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.name = "customfs",
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.mount = fs_mount,
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.name = FS_NAME,
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.mount = mount_fs,
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.kill_sb = kill_litter_super,
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};
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static int __init fs_init(void) {
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hash_init(link_table);
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printk(KERN_INFO "customfs: module loaded\n");
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return register_filesystem(&fs_type);
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}
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static void __exit fs_exit(void) {
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unregister_filesystem(&fs_type);
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printk(KERN_INFO "customfs: module unloaded\n");
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}
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module_init(fs_init);
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module_exit(fs_exit);
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14
t.bash
Executable file
14
t.bash
Executable file
@ -0,0 +1,14 @@
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#!/bin/bash
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# создать файл
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echo test > /mnt/customfs/books/hello.txt
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# создать подкаталог
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mkdir /mnt/customfs/authors/kirill
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# создать жёсткую ссылку
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ln /mnt/customfs/books/hello.txt /mnt/customfs/authors/kirill/hlink
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# удалить исходный файл
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rm /mnt/customfs/books/hello.txt
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# => ссылка в authors также исчезнет
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