// SPDX-License-Identifier: GPL-2.0
/*
 *  linux/fs/proc/inode.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 */

#include <linux/cache.h>
#include <linux/time.h>
#include <linux/proc_fs.h>
#include <linux/kernel.h>
#include <linux/pid_namespace.h>
#include <linux/mm.h>
#include <linux/string.h>
#include <linux/stat.h>
#include <linux/completion.h>
#include <linux/poll.h>
#include <linux/printk.h>
#include <linux/file.h>
#include <linux/limits.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/sysctl.h>
#include <linux/seq_file.h>
#include <linux/slab.h>
#include <linux/mount.h>
#include <linux/magic.h>

#include <linux/uaccess.h>

#include "internal.h"

static void proc_evict_inode(struct inode *inode)
{
        struct proc_dir_entry *de;
        struct ctl_table_header *head;

        truncate_inode_pages_final(&inode->i_data);
        clear_inode(inode);

        /* Stop tracking associated processes */
        put_pid(PROC_I(inode)->pid);

        /* Let go of any associated proc directory entry */
        de = PDE(inode);
        if (de)
                pde_put(de);

        head = PROC_I(inode)->sysctl;
        if (head) {
                RCU_INIT_POINTER(PROC_I(inode)->sysctl, NULL);
                proc_sys_evict_inode(inode, head);
        }
}

static struct kmem_cache *proc_inode_cachep __ro_after_init;
static struct kmem_cache *pde_opener_cache __ro_after_init;

static struct inode *proc_alloc_inode(struct super_block *sb)
{
        struct proc_inode *ei;
        struct inode *inode;

        ei = kmem_cache_alloc(proc_inode_cachep, GFP_KERNEL);
        if (!ei)
                return NULL;
        ei->pid = NULL;
        ei->fd = 0;
        ei->op.proc_get_link = NULL;
        ei->pde = NULL;
        ei->sysctl = NULL;
        ei->sysctl_entry = NULL;
        ei->ns_ops = NULL;
        inode = &ei->vfs_inode;
        return inode;
}

static void proc_i_callback(struct rcu_head *head)
{
        struct inode *inode = container_of(head, struct inode, i_rcu);
        kmem_cache_free(proc_inode_cachep, PROC_I(inode));
}

static void proc_destroy_inode(struct inode *inode)
{
        call_rcu(&inode->i_rcu, proc_i_callback);
}

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

        inode_init_once(&ei->vfs_inode);
}

void __init proc_init_kmemcache(void)
{
        proc_inode_cachep = kmem_cache_create("proc_inode_cache",
                                             sizeof(struct proc_inode),
                                             0, (SLAB_RECLAIM_ACCOUNT|
                                                SLAB_MEM_SPREAD|SLAB_ACCOUNT|
                                                SLAB_PANIC),
                                             init_once);
        pde_opener_cache =
                kmem_cache_create("pde_opener", sizeof(struct pde_opener), 0,
                                  SLAB_ACCOUNT|SLAB_PANIC, NULL);
        proc_dir_entry_cache = kmem_cache_create_usercopy(
                "proc_dir_entry", sizeof(struct proc_dir_entry), 0, SLAB_PANIC,
                offsetof(struct proc_dir_entry, inline_name),
                sizeof_field(struct proc_dir_entry, inline_name), NULL);
}

static int proc_show_options(struct seq_file *seq, struct dentry *root)
{
        struct super_block *sb = root->d_sb;
        struct pid_namespace *pid = sb->s_fs_info;

        if (!gid_eq(pid->pid_gid, GLOBAL_ROOT_GID))
                seq_printf(seq, ",gid=%u", from_kgid_munged(&init_user_ns, pid->pid_gid));
        if (pid->hide_pid != HIDEPID_OFF)
                seq_printf(seq, ",hidepid=%u", pid->hide_pid);

        return 0;
}

static const struct super_operations proc_sops = {
        .alloc_inode    = proc_alloc_inode,
        .destroy_inode  = proc_destroy_inode,
        .drop_inode     = generic_delete_inode,
        .evict_inode    = proc_evict_inode,
        .statfs         = simple_statfs,
        .remount_fs     = proc_remount,
        .show_options   = proc_show_options,
};

enum {BIAS = -1U<<31};

static inline int use_pde(struct proc_dir_entry *pde)
{
        return likely(atomic_inc_unless_negative(&pde->in_use));
}

static void unuse_pde(struct proc_dir_entry *pde)
{
        if (unlikely(atomic_dec_return(&pde->in_use) == BIAS))
                complete(pde->pde_unload_completion);
}

/* pde is locked on entry, unlocked on exit */
static void close_pdeo(struct proc_dir_entry *pde, struct pde_opener *pdeo)
{
        /*
         * close() (proc_reg_release()) can't delete an entry and proceed:
         * ->release hook needs to be available at the right moment.
         *
         * rmmod (remove_proc_entry() et al) can't delete an entry and proceed:
         * "struct file" needs to be available at the right moment.
         *
         * Therefore, first process to enter this function does ->release() and
         * signals its completion to the other process which does nothing.
         */
        if (pdeo->closing) {
                /* somebody else is doing that, just wait */
                DECLARE_COMPLETION_ONSTACK(c);
                pdeo->c = &c;
                spin_unlock(&pde->pde_unload_lock);
                wait_for_completion(&c);
        } else {
                struct file *file;
                struct completion *c;

                pdeo->closing = true;
                spin_unlock(&pde->pde_unload_lock);
                file = pdeo->file;
                pde->proc_fops->release(file_inode(file), file);
                spin_lock(&pde->pde_unload_lock);
                /* After ->release. */
                list_del(&pdeo->lh);
                c = pdeo->c;
                spin_unlock(&pde->pde_unload_lock);
                if (unlikely(c))
                        complete(c);
                kmem_cache_free(pde_opener_cache, pdeo);
        }
}

void proc_entry_rundown(struct proc_dir_entry *de)
{
        DECLARE_COMPLETION_ONSTACK(c);
        /* Wait until all existing callers into module are done. */
        de->pde_unload_completion = &c;
        if (atomic_add_return(BIAS, &de->in_use) != BIAS)
                wait_for_completion(&c);

        /* ->pde_openers list can't grow from now on. */

        spin_lock(&de->pde_unload_lock);
        while (!list_empty(&de->pde_openers)) {
                struct pde_opener *pdeo;
                pdeo = list_first_entry(&de->pde_openers, struct pde_opener, lh);
                close_pdeo(de, pdeo);
                spin_lock(&de->pde_unload_lock);
        }
        spin_unlock(&de->pde_unload_lock);
}

static loff_t proc_reg_llseek(struct file *file, loff_t offset, int whence)
{
        struct proc_dir_entry *pde = PDE(file_inode(file));
        loff_t rv = -EINVAL;
        if (use_pde(pde)) {
                loff_t (*llseek)(struct file *, loff_t, int);
                llseek = pde->proc_fops->llseek;
                if (!llseek)
                        llseek = default_llseek;
                rv = llseek(file, offset, whence);
                unuse_pde(pde);
        }
        return rv;
}

static ssize_t proc_reg_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
{
        ssize_t (*read)(struct file *, char __user *, size_t, loff_t *);
        struct proc_dir_entry *pde = PDE(file_inode(file));
        ssize_t rv = -EIO;
        if (use_pde(pde)) {
                read = pde->proc_fops->read;
                if (read)
                        rv = read(file, buf, count, ppos);
                unuse_pde(pde);
        }
        return rv;
}

static ssize_t proc_reg_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
{
        ssize_t (*write)(struct file *, const char __user *, size_t, loff_t *);
        struct proc_dir_entry *pde = PDE(file_inode(file));
        ssize_t rv = -EIO;
        if (use_pde(pde)) {
                write = pde->proc_fops->write;
                if (write)
                        rv = write(file, buf, count, ppos);
                unuse_pde(pde);
        }
        return rv;
}

static __poll_t proc_reg_poll(struct file *file, struct poll_table_struct *pts)
{
        struct proc_dir_entry *pde = PDE(file_inode(file));
        __poll_t rv = DEFAULT_POLLMASK;
        __poll_t (*poll)(struct file *, struct poll_table_struct *);
        if (use_pde(pde)) {
                poll = pde->proc_fops->poll;
                if (poll)
                        rv = poll(file, pts);
                unuse_pde(pde);
        }
        return rv;
}

static long proc_reg_unlocked_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
        struct proc_dir_entry *pde = PDE(file_inode(file));
        long rv = -ENOTTY;
        long (*ioctl)(struct file *, unsigned int, unsigned long);
        if (use_pde(pde)) {
                ioctl = pde->proc_fops->unlocked_ioctl;
                if (ioctl)
                        rv = ioctl(file, cmd, arg);
                unuse_pde(pde);
        }
        return rv;
}

#ifdef CONFIG_COMPAT
static long proc_reg_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
        struct proc_dir_entry *pde = PDE(file_inode(file));
        long rv = -ENOTTY;
        long (*compat_ioctl)(struct file *, unsigned int, unsigned long);
        if (use_pde(pde)) {
                compat_ioctl = pde->proc_fops->compat_ioctl;
                if (compat_ioctl)
                        rv = compat_ioctl(file, cmd, arg);
                unuse_pde(pde);
        }
        return rv;
}
#endif

static int proc_reg_mmap(struct file *file, struct vm_area_struct *vma)
{
        struct proc_dir_entry *pde = PDE(file_inode(file));
        int rv = -EIO;
        int (*mmap)(struct file *, struct vm_area_struct *);
        if (use_pde(pde)) {
                mmap = pde->proc_fops->mmap;
                if (mmap)
                        rv = mmap(file, vma);
                unuse_pde(pde);
        }
        return rv;
}

static unsigned long
proc_reg_get_unmapped_area(struct file *file, unsigned long orig_addr,
                           unsigned long len, unsigned long pgoff,
                           unsigned long flags)
{
        struct proc_dir_entry *pde = PDE(file_inode(file));
        unsigned long rv = -EIO;

        if (use_pde(pde)) {
                typeof(proc_reg_get_unmapped_area) *get_area;

                get_area = pde->proc_fops->get_unmapped_area;
#ifdef CONFIG_MMU
                if (!get_area)
                        get_area = current->mm->get_unmapped_area;
#endif

                if (get_area)
                        rv = get_area(file, orig_addr, len, pgoff, flags);
                else
                        rv = orig_addr;
                unuse_pde(pde);
        }
        return rv;
}

static int proc_reg_open(struct inode *inode, struct file *file)
{
        struct proc_dir_entry *pde = PDE(inode);
        int rv = 0;
        int (*open)(struct inode *, struct file *);
        int (*release)(struct inode *, struct file *);
        struct pde_opener *pdeo;

        /*
         * Ensure that
         * 1) PDE's ->release hook will be called no matter what
         *    either normally by close()/->release, or forcefully by
         *    rmmod/remove_proc_entry.
         *
         * 2) rmmod isn't blocked by opening file in /proc and sitting on
         *    the descriptor (including "rmmod foo </proc/foo" scenario).
         *
         * Save every "struct file" with custom ->release hook.
         */
        if (!use_pde(pde))
                return -ENOENT;

        release = pde->proc_fops->release;
        if (release) {
                pdeo = kmem_cache_alloc(pde_opener_cache, GFP_KERNEL);
                if (!pdeo) {
                        rv = -ENOMEM;
                        goto out_unuse;
                }
        }

        open = pde->proc_fops->open;
        if (open)
                rv = open(inode, file);

        if (release) {
                if (rv == 0) {
                        /* To know what to release. */
                        pdeo->file = file;
                        pdeo->closing = false;
                        pdeo->c = NULL;
                        spin_lock(&pde->pde_unload_lock);
                        list_add(&pdeo->lh, &pde->pde_openers);
                        spin_unlock(&pde->pde_unload_lock);
                } else
                        kmem_cache_free(pde_opener_cache, pdeo);
        }

out_unuse:
        unuse_pde(pde);
        return rv;
}

static int proc_reg_release(struct inode *inode, struct file *file)
{
        struct proc_dir_entry *pde = PDE(inode);
        struct pde_opener *pdeo;
        spin_lock(&pde->pde_unload_lock);
        list_for_each_entry(pdeo, &pde->pde_openers, lh) {
                if (pdeo->file == file) {
                        close_pdeo(pde, pdeo);
                        return 0;
                }
        }
        spin_unlock(&pde->pde_unload_lock);
        return 0;
}

static const struct file_operations proc_reg_file_ops = {
        .llseek         = proc_reg_llseek,
        .read           = proc_reg_read,
        .write          = proc_reg_write,
        .poll           = proc_reg_poll,
        .unlocked_ioctl = proc_reg_unlocked_ioctl,
#ifdef CONFIG_COMPAT
        .compat_ioctl   = proc_reg_compat_ioctl,
#endif
        .mmap           = proc_reg_mmap,
        .get_unmapped_area = proc_reg_get_unmapped_area,
        .open           = proc_reg_open,
        .release        = proc_reg_release,
};

#ifdef CONFIG_COMPAT
static const struct file_operations proc_reg_file_ops_no_compat = {
        .llseek         = proc_reg_llseek,
        .read           = proc_reg_read,
        .write          = proc_reg_write,
        .poll           = proc_reg_poll,
        .unlocked_ioctl = proc_reg_unlocked_ioctl,
        .mmap           = proc_reg_mmap,
        .get_unmapped_area = proc_reg_get_unmapped_area,
        .open           = proc_reg_open,
        .release        = proc_reg_release,
};
#endif

static void proc_put_link(void *p)
{
        unuse_pde(p);
}

static const char *proc_get_link(struct dentry *dentry,
                                 struct inode *inode,
                                 struct delayed_call *done)
{
        struct proc_dir_entry *pde = PDE(inode);
        if (!use_pde(pde))
                return ERR_PTR(-EINVAL);
        set_delayed_call(done, proc_put_link, pde);
        return pde->data;
}

const struct inode_operations proc_link_inode_operations = {
        .get_link       = proc_get_link,
};

struct inode *proc_get_inode(struct super_block *sb, struct proc_dir_entry *de)
{
        struct inode *inode = new_inode_pseudo(sb);

        if (inode) {
                inode->i_ino = de->low_ino;
                inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
                PROC_I(inode)->pde = de;

                if (is_empty_pde(de)) {
                        make_empty_dir_inode(inode);
                        return inode;
                }
                if (de->mode) {
                        inode->i_mode = de->mode;
                        inode->i_uid = de->uid;
                        inode->i_gid = de->gid;
                }
                if (de->size)
                        inode->i_size = de->size;
                if (de->nlink)
                        set_nlink(inode, de->nlink);
                WARN_ON(!de->proc_iops);
                inode->i_op = de->proc_iops;
                if (de->proc_fops) {
                        if (S_ISREG(inode->i_mode)) {
#ifdef CONFIG_COMPAT
                                if (!de->proc_fops->compat_ioctl)
                                        inode->i_fop =
                                                &proc_reg_file_ops_no_compat;
                                else
#endif
                                        inode->i_fop = &proc_reg_file_ops;
                        } else {
                                inode->i_fop = de->proc_fops;
                        }
                }
        } else
               pde_put(de);
        return inode;
}

int proc_fill_super(struct super_block *s, void *data, int silent)
{
        struct pid_namespace *ns = get_pid_ns(s->s_fs_info);
        struct inode *root_inode;
        int ret;

        if (!proc_parse_options(data, ns))
                return -EINVAL;

        /* User space would break if executables or devices appear on proc */
        s->s_iflags |= SB_I_USERNS_VISIBLE | SB_I_NOEXEC | SB_I_NODEV;
        s->s_flags |= SB_NODIRATIME | SB_NOSUID | SB_NOEXEC;
        s->s_blocksize = 1024;
        s->s_blocksize_bits = 10;
        s->s_magic = PROC_SUPER_MAGIC;
        s->s_op = &proc_sops;
        s->s_time_gran = 1;

        /*
         * procfs isn't actually a stacking filesystem; however, there is
         * too much magic going on inside it to permit stacking things on
         * top of it
         */
        s->s_stack_depth = FILESYSTEM_MAX_STACK_DEPTH;
        
        pde_get(&proc_root);
        root_inode = proc_get_inode(s, &proc_root);
        if (!root_inode) {
                pr_err("proc_fill_super: get root inode failed\n");
                return -ENOMEM;
        }

        s->s_root = d_make_root(root_inode);
        if (!s->s_root) {
                pr_err("proc_fill_super: allocate dentry failed\n");
                return -ENOMEM;
        }

        ret = proc_setup_self(s);
        if (ret) {
                return ret;
        }
        return proc_setup_thread_self(s);
}