// 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/bug.h>

#include "internal.h"

static void proc_evict_inode(struct inode *inode)
{
        struct ctl_table_header *head;
        struct proc_inode *ei = PROC_I(inode);

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

        /* Stop tracking associated processes */
        if (ei->pid)
                proc_pid_evict_inode(ei);

        head = ei->sysctl;
        if (head) {
                WRITE_ONCE(ei->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;

        ei = alloc_inode_sb(sb, 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;
        INIT_HLIST_NODE(&ei->sibling_inodes);
        ei->ns_ops = NULL;
        return &ei->vfs_inode;
}

static void proc_free_inode(struct inode *inode)
{
        struct proc_inode *ei = PROC_I(inode);

        if (ei->pid)
                put_pid(ei->pid);
        /* Let go of any associated proc directory entry */
        if (ei->pde)
                pde_put(ei->pde);
        kmem_cache_free(proc_inode_cachep, PROC_I(inode));
}

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_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_PDE, 0, SLAB_PANIC,
                offsetof(struct proc_dir_entry, inline_name),
                SIZEOF_PDE_INLINE_NAME, NULL);
        BUILD_BUG_ON(sizeof(struct proc_dir_entry) >= SIZEOF_PDE);
}

void proc_invalidate_siblings_dcache(struct hlist_head *inodes, spinlock_t *lock)
{
        struct hlist_node *node;
        struct super_block *old_sb = NULL;

        rcu_read_lock();
        while ((node = hlist_first_rcu(inodes))) {
                struct proc_inode *ei = hlist_entry(node, struct proc_inode, sibling_inodes);
                struct super_block *sb;
                struct inode *inode;

                spin_lock(lock);
                hlist_del_init_rcu(&ei->sibling_inodes);
                spin_unlock(lock);

                inode = &ei->vfs_inode;
                sb = inode->i_sb;
                if ((sb != old_sb) && !atomic_inc_not_zero(&sb->s_active))
                        continue;
                inode = igrab(inode);
                rcu_read_unlock();
                if (sb != old_sb) {
                        if (old_sb)
                                deactivate_super(old_sb);
                        old_sb = sb;
                }
                if (unlikely(!inode)) {
                        rcu_read_lock();
                        continue;
                }

                if (S_ISDIR(inode->i_mode)) {
                        struct dentry *dir = d_find_any_alias(inode);
                        if (dir) {
                                d_invalidate(dir);
                                dput(dir);
                        }
                } else {
                        struct dentry *dentry;
                        while ((dentry = d_find_alias(inode))) {
                                d_invalidate(dentry);
                                dput(dentry);
                        }
                }
                iput(inode);

                rcu_read_lock();
        }
        rcu_read_unlock();
        if (old_sb)
                deactivate_super(old_sb);
}

static inline const char *hidepid2str(enum proc_hidepid v)
{
        switch (v) {
                case HIDEPID_OFF: return "off";
                case HIDEPID_NO_ACCESS: return "noaccess";
                case HIDEPID_INVISIBLE: return "invisible";
                case HIDEPID_NOT_PTRACEABLE: return "ptraceable";
        }
        WARN_ONCE(1, "bad hide_pid value: %d\n", v);
        return "unknown";
}

static int proc_show_options(struct seq_file *seq, struct dentry *root)
{
        struct proc_fs_info *fs_info = proc_sb_info(root->d_sb);

        if (!gid_eq(fs_info->pid_gid, GLOBAL_ROOT_GID))
                seq_printf(seq, ",gid=%u", from_kgid_munged(&init_user_ns, fs_info->pid_gid));
        if (fs_info->hide_pid != HIDEPID_OFF)
                seq_printf(seq, ",hidepid=%s", hidepid2str(fs_info->hide_pid));
        if (fs_info->pidonly != PROC_PIDONLY_OFF)
                seq_printf(seq, ",subset=pid");

        return 0;
}

const struct super_operations proc_sops = {
        .alloc_inode    = proc_alloc_inode,
        .free_inode     = proc_free_inode,
        .drop_inode     = inode_just_drop,
        .evict_inode    = proc_evict_inode,
        .statfs         = simple_statfs,
        .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);
}

/*
 * At most 2 contexts can enter this function: the one doing the last
 * close on the descriptor and whoever is deleting PDE itself.
 *
 * First to enter calls ->proc_release hook and signals its completion
 * to the second one which waits and then does nothing.
 *
 * PDE is locked on entry, unlocked on exit.
 */
static void close_pdeo(struct proc_dir_entry *pde, struct pde_opener *pdeo)
        __releases(&pde->pde_unload_lock)
{
        /*
         * 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.
         */
        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_ops->proc_release(file_inode(file), file);

                spin_lock(&pde->pde_unload_lock);
                /* Strictly after ->proc_release, see above. */
                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 (pde_is_permanent(pde)) {
                return pde->proc_ops->proc_lseek(file, offset, whence);
        } else if (use_pde(pde)) {
                rv = pde->proc_ops->proc_lseek(file, offset, whence);
                unuse_pde(pde);
        }
        return rv;
}

static ssize_t proc_reg_read_iter(struct kiocb *iocb, struct iov_iter *iter)
{
        struct proc_dir_entry *pde = PDE(file_inode(iocb->ki_filp));
        ssize_t ret;

        if (pde_is_permanent(pde))
                return pde->proc_ops->proc_read_iter(iocb, iter);

        if (!use_pde(pde))
                return -EIO;
        ret = pde->proc_ops->proc_read_iter(iocb, iter);
        unuse_pde(pde);
        return ret;
}

static ssize_t pde_read(struct proc_dir_entry *pde, struct file *file, char __user *buf, size_t count, loff_t *ppos)
{
        const auto read = pde->proc_ops->proc_read;
        if (read)
                return read(file, buf, count, ppos);
        return -EIO;
}

static ssize_t proc_reg_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
{
        struct proc_dir_entry *pde = PDE(file_inode(file));
        ssize_t rv = -EIO;

        if (pde_is_permanent(pde)) {
                return pde_read(pde, file, buf, count, ppos);
        } else if (use_pde(pde)) {
                rv = pde_read(pde, file, buf, count, ppos);
                unuse_pde(pde);
        }
        return rv;
}

static ssize_t pde_write(struct proc_dir_entry *pde, struct file *file, const char __user *buf, size_t count, loff_t *ppos)
{
        const auto write = pde->proc_ops->proc_write;
        if (write)
                return write(file, buf, count, ppos);
        return -EIO;
}

static ssize_t proc_reg_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
{
        struct proc_dir_entry *pde = PDE(file_inode(file));
        ssize_t rv = -EIO;

        if (pde_is_permanent(pde)) {
                return pde_write(pde, file, buf, count, ppos);
        } else if (use_pde(pde)) {
                rv = pde_write(pde, file, buf, count, ppos);
                unuse_pde(pde);
        }
        return rv;
}

static __poll_t pde_poll(struct proc_dir_entry *pde, struct file *file, struct poll_table_struct *pts)
{
        const auto poll = pde->proc_ops->proc_poll;
        if (poll)
                return poll(file, pts);
        return DEFAULT_POLLMASK;
}

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;

        if (pde_is_permanent(pde)) {
                return pde_poll(pde, file, pts);
        } else if (use_pde(pde)) {
                rv = pde_poll(pde, file, pts);
                unuse_pde(pde);
        }
        return rv;
}

static long pde_ioctl(struct proc_dir_entry *pde, struct file *file, unsigned int cmd, unsigned long arg)
{
        const auto ioctl = pde->proc_ops->proc_ioctl;
        if (ioctl)
                return ioctl(file, cmd, arg);
        return -ENOTTY;
}

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;

        if (pde_is_permanent(pde)) {
                return pde_ioctl(pde, file, cmd, arg);
        } else if (use_pde(pde)) {
                rv = pde_ioctl(pde, file, cmd, arg);
                unuse_pde(pde);
        }
        return rv;
}

#ifdef CONFIG_COMPAT
static long pde_compat_ioctl(struct proc_dir_entry *pde, struct file *file, unsigned int cmd, unsigned long arg)
{
        const auto compat_ioctl = pde->proc_ops->proc_compat_ioctl;
        if (compat_ioctl)
                return compat_ioctl(file, cmd, arg);
        return -ENOTTY;
}

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;
        if (pde_is_permanent(pde)) {
                return pde_compat_ioctl(pde, file, cmd, arg);
        } else if (use_pde(pde)) {
                rv = pde_compat_ioctl(pde, file, cmd, arg);
                unuse_pde(pde);
        }
        return rv;
}
#endif

static int pde_mmap(struct proc_dir_entry *pde, struct file *file, struct vm_area_struct *vma)
{
        const auto mmap = pde->proc_ops->proc_mmap;
        if (mmap)
                return mmap(file, vma);
        return -EIO;
}

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;

        if (pde_is_permanent(pde)) {
                return pde_mmap(pde, file, vma);
        } else if (use_pde(pde)) {
                rv = pde_mmap(pde, file, vma);
                unuse_pde(pde);
        }
        return rv;
}

static unsigned long
pde_get_unmapped_area(struct proc_dir_entry *pde, struct file *file, unsigned long orig_addr,
                           unsigned long len, unsigned long pgoff,
                           unsigned long flags)
{
        if (pde->proc_ops->proc_get_unmapped_area)
                return pde->proc_ops->proc_get_unmapped_area(file, orig_addr, len, pgoff, flags);

#ifdef CONFIG_MMU
        return mm_get_unmapped_area(file, orig_addr, len, pgoff, flags);
#endif

        return orig_addr;
}

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 (pde_is_permanent(pde)) {
                return pde_get_unmapped_area(pde, file, orig_addr, len, pgoff, flags);
        } else if (use_pde(pde)) {
                rv = pde_get_unmapped_area(pde, file, orig_addr, len, pgoff, flags);
                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;
        typeof_member(struct proc_ops, proc_open) open;
        struct pde_opener *pdeo;

        if (!pde_has_proc_lseek(pde))
                file->f_mode &= ~FMODE_LSEEK;

        if (pde_is_permanent(pde)) {
                open = pde->proc_ops->proc_open;
                if (open)
                        rv = open(inode, file);
                return rv;
        }

        /*
         * 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;

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

        open = pde->proc_ops->proc_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;

        if (pde_is_permanent(pde)) {
                const auto release = pde->proc_ops->proc_release;
                if (release)
                        return release(inode, file);
                return 0;
        }

        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,
        .mmap           = proc_reg_mmap,
        .get_unmapped_area = proc_reg_get_unmapped_area,
        .open           = proc_reg_open,
        .release        = proc_reg_release,
};

static const struct file_operations proc_iter_file_ops = {
        .llseek         = proc_reg_llseek,
        .read_iter      = proc_reg_read_iter,
        .write          = proc_reg_write,
        .splice_read    = copy_splice_read,
        .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,
};

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

static const struct file_operations proc_iter_file_ops_compat = {
        .llseek         = proc_reg_llseek,
        .read_iter      = proc_reg_read_iter,
        .splice_read    = copy_splice_read,
        .write          = proc_reg_write,
        .poll           = proc_reg_poll,
        .unlocked_ioctl = proc_reg_unlocked_ioctl,
        .compat_ioctl   = proc_reg_compat_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(sb);

        if (!inode) {
                pde_put(de);
                return NULL;
        }

        inode->i_private = de->data;
        inode->i_ino = de->low_ino;
        simple_inode_init_ts(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);

        if (S_ISREG(inode->i_mode)) {
                inode->i_op = de->proc_iops;
                if (pde_has_proc_read_iter(de))
                        inode->i_fop = &proc_iter_file_ops;
                else
                        inode->i_fop = &proc_reg_file_ops;
#ifdef CONFIG_COMPAT
                if (pde_has_proc_compat_ioctl(de)) {
                        if (pde_has_proc_read_iter(de))
                                inode->i_fop = &proc_iter_file_ops_compat;
                        else
                                inode->i_fop = &proc_reg_file_ops_compat;
                }
#endif
        } else if (S_ISDIR(inode->i_mode)) {
                inode->i_op = de->proc_iops;
                inode->i_fop = de->proc_dir_ops;
        } else if (S_ISLNK(inode->i_mode)) {
                inode->i_op = de->proc_iops;
                inode->i_fop = NULL;
        } else {
                BUG();
        }
        return inode;
}