// SPDX-License-Identifier: GPL-2.0-only
/*
 *  linux/fs/proc/net.c
 *
 *  Copyright (C) 2007
 *
 *  Author: Eric Biederman <ebiederm@xmission.com>
 *
 *  proc net directory handling functions
 */
#include <linux/errno.h>
#include <linux/time.h>
#include <linux/proc_fs.h>
#include <linux/stat.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/sched/task.h>
#include <linux/module.h>
#include <linux/bitops.h>
#include <linux/mount.h>
#include <linux/nsproxy.h>
#include <linux/uidgid.h>
#include <net/net_namespace.h>
#include <linux/seq_file.h>

#include "internal.h"

static inline struct net *PDE_NET(struct proc_dir_entry *pde)
{
        return pde->parent->data;
}

static struct net *get_proc_net(const struct inode *inode)
{
        return maybe_get_net(PDE_NET(PDE(inode)));
}

static int seq_open_net(struct inode *inode, struct file *file)
{
        unsigned int state_size = PDE(inode)->state_size;
        struct seq_net_private *p;
        struct net *net;

        WARN_ON_ONCE(state_size < sizeof(*p));

        if (file->f_mode & FMODE_WRITE && !PDE(inode)->write)
                return -EACCES;

        net = get_proc_net(inode);
        if (!net)
                return -ENXIO;

        p = __seq_open_private(file, PDE(inode)->seq_ops, state_size);
        if (!p) {
                put_net(net);
                return -ENOMEM;
        }
#ifdef CONFIG_NET_NS
        p->net = net;
        netns_tracker_alloc(net, &p->ns_tracker, GFP_KERNEL);
#endif
        return 0;
}

static void seq_file_net_put_net(struct seq_file *seq)
{
#ifdef CONFIG_NET_NS
        struct seq_net_private *priv = seq->private;

        put_net_track(priv->net, &priv->ns_tracker);
#else
        put_net(&init_net);
#endif
}

static int seq_release_net(struct inode *ino, struct file *f)
{
        struct seq_file *seq = f->private_data;

        seq_file_net_put_net(seq);
        seq_release_private(ino, f);
        return 0;
}

static const struct proc_ops proc_net_seq_ops = {
        .proc_open      = seq_open_net,
        .proc_read      = seq_read,
        .proc_write     = proc_simple_write,
        .proc_lseek     = seq_lseek,
        .proc_release   = seq_release_net,
};

int bpf_iter_init_seq_net(void *priv_data, struct bpf_iter_aux_info *aux)
{
#ifdef CONFIG_NET_NS
        struct seq_net_private *p = priv_data;

        p->net = get_net_track(current->nsproxy->net_ns, &p->ns_tracker,
                               GFP_KERNEL);
#endif
        return 0;
}

void bpf_iter_fini_seq_net(void *priv_data)
{
#ifdef CONFIG_NET_NS
        struct seq_net_private *p = priv_data;

        put_net_track(p->net, &p->ns_tracker);
#endif
}

struct proc_dir_entry *proc_create_net_data(const char *name, umode_t mode,
                struct proc_dir_entry *parent, const struct seq_operations *ops,
                unsigned int state_size, void *data)
{
        struct proc_dir_entry *p;

        p = proc_create_reg(name, mode, &parent, data);
        if (!p)
                return NULL;
        pde_force_lookup(p);
        p->proc_ops = &proc_net_seq_ops;
        p->seq_ops = ops;
        p->state_size = state_size;
        return proc_register(parent, p);
}
EXPORT_SYMBOL_GPL(proc_create_net_data);

/**
 * proc_create_net_data_write - Create a writable net_ns-specific proc file
 * @name: The name of the file.
 * @mode: The file's access mode.
 * @parent: The parent directory in which to create.
 * @ops: The seq_file ops with which to read the file.
 * @write: The write method with which to 'modify' the file.
 * @state_size: The size of the per-file private state to allocate.
 * @data: Data for retrieval by pde_data().
 *
 * Create a network namespaced proc file in the @parent directory with the
 * specified @name and @mode that allows reading of a file that displays a
 * series of elements and also provides for the file accepting writes that have
 * some arbitrary effect.
 *
 * The functions in the @ops table are used to iterate over items to be
 * presented and extract the readable content using the seq_file interface.
 *
 * The @write function is called with the data copied into a kernel space
 * scratch buffer and has a NUL appended for convenience.  The buffer may be
 * modified by the @write function.  @write should return 0 on success.
 *
 * The @data value is accessible from the @show and @write functions by calling
 * pde_data() on the file inode.  The network namespace must be accessed by
 * calling seq_file_net() on the seq_file struct.
 */
struct proc_dir_entry *proc_create_net_data_write(const char *name, umode_t mode,
                                                  struct proc_dir_entry *parent,
                                                  const struct seq_operations *ops,
                                                  proc_write_t write,
                                                  unsigned int state_size, void *data)
{
        struct proc_dir_entry *p;

        p = proc_create_reg(name, mode, &parent, data);
        if (!p)
                return NULL;
        pde_force_lookup(p);
        p->proc_ops = &proc_net_seq_ops;
        p->seq_ops = ops;
        p->state_size = state_size;
        p->write = write;
        return proc_register(parent, p);
}
EXPORT_SYMBOL_GPL(proc_create_net_data_write);

static int single_open_net(struct inode *inode, struct file *file)
{
        struct proc_dir_entry *de = PDE(inode);
        struct net *net;
        int err;

        net = get_proc_net(inode);
        if (!net)
                return -ENXIO;

        err = single_open(file, de->single_show, net);
        if (err)
                put_net(net);
        return err;
}

static int single_release_net(struct inode *ino, struct file *f)
{
        struct seq_file *seq = f->private_data;
        put_net(seq->private);
        return single_release(ino, f);
}

static const struct proc_ops proc_net_single_ops = {
        .proc_open      = single_open_net,
        .proc_read      = seq_read,
        .proc_write     = proc_simple_write,
        .proc_lseek     = seq_lseek,
        .proc_release   = single_release_net,
};

struct proc_dir_entry *proc_create_net_single(const char *name, umode_t mode,
                struct proc_dir_entry *parent,
                int (*show)(struct seq_file *, void *), void *data)
{
        struct proc_dir_entry *p;

        p = proc_create_reg(name, mode, &parent, data);
        if (!p)
                return NULL;
        pde_force_lookup(p);
        p->proc_ops = &proc_net_single_ops;
        p->single_show = show;
        return proc_register(parent, p);
}
EXPORT_SYMBOL_GPL(proc_create_net_single);

/**
 * proc_create_net_single_write - Create a writable net_ns-specific proc file
 * @name: The name of the file.
 * @mode: The file's access mode.
 * @parent: The parent directory in which to create.
 * @show: The seqfile show method with which to read the file.
 * @write: The write method with which to 'modify' the file.
 * @data: Data for retrieval by pde_data().
 *
 * Create a network-namespaced proc file in the @parent directory with the
 * specified @name and @mode that allows reading of a file that displays a
 * single element rather than a series and also provides for the file accepting
 * writes that have some arbitrary effect.
 *
 * The @show function is called to extract the readable content via the
 * seq_file interface.
 *
 * The @write function is called with the data copied into a kernel space
 * scratch buffer and has a NUL appended for convenience.  The buffer may be
 * modified by the @write function.  @write should return 0 on success.
 *
 * The @data value is accessible from the @show and @write functions by calling
 * pde_data() on the file inode.  The network namespace must be accessed by
 * calling seq_file_single_net() on the seq_file struct.
 */
struct proc_dir_entry *proc_create_net_single_write(const char *name, umode_t mode,
                                                    struct proc_dir_entry *parent,
                                                    int (*show)(struct seq_file *, void *),
                                                    proc_write_t write,
                                                    void *data)
{
        struct proc_dir_entry *p;

        p = proc_create_reg(name, mode, &parent, data);
        if (!p)
                return NULL;
        pde_force_lookup(p);
        p->proc_ops = &proc_net_single_ops;
        p->single_show = show;
        p->write = write;
        return proc_register(parent, p);
}
EXPORT_SYMBOL_GPL(proc_create_net_single_write);

static struct net *get_proc_task_net(struct inode *dir)
{
        struct task_struct *task;
        struct nsproxy *ns;
        struct net *net = NULL;

        rcu_read_lock();
        task = pid_task(proc_pid(dir), PIDTYPE_PID);
        if (task != NULL) {
                task_lock(task);
                ns = task->nsproxy;
                if (ns != NULL)
                        net = get_net(ns->net_ns);
                task_unlock(task);
        }
        rcu_read_unlock();

        return net;
}

static struct dentry *proc_tgid_net_lookup(struct inode *dir,
                struct dentry *dentry, unsigned int flags)
{
        struct dentry *de;
        struct net *net;

        de = ERR_PTR(-ENOENT);
        net = get_proc_task_net(dir);
        if (net != NULL) {
                de = proc_lookup_de(dir, dentry, net->proc_net);
                put_net(net);
        }
        return de;
}

static int proc_tgid_net_getattr(struct mnt_idmap *idmap,
                                 const struct path *path, struct kstat *stat,
                                 u32 request_mask, unsigned int query_flags)
{
        struct inode *inode = d_inode(path->dentry);
        struct net *net;

        net = get_proc_task_net(inode);

        generic_fillattr(&nop_mnt_idmap, request_mask, inode, stat);

        if (net != NULL) {
                stat->nlink = net->proc_net->nlink;
                put_net(net);
        }

        return 0;
}

const struct inode_operations proc_net_inode_operations = {
        .lookup         = proc_tgid_net_lookup,
        .getattr        = proc_tgid_net_getattr,
        .setattr        = proc_setattr,
};

static int proc_tgid_net_readdir(struct file *file, struct dir_context *ctx)
{
        int ret;
        struct net *net;

        ret = -EINVAL;
        net = get_proc_task_net(file_inode(file));
        if (net != NULL) {
                ret = proc_readdir_de(file, ctx, net->proc_net);
                put_net(net);
        }
        return ret;
}

const struct file_operations proc_net_operations = {
        .llseek         = generic_file_llseek,
        .read           = generic_read_dir,
        .iterate_shared = proc_tgid_net_readdir,
};

static __net_init int proc_net_ns_init(struct net *net)
{
        struct proc_dir_entry *netd, *net_statd;
        kuid_t uid;
        kgid_t gid;
        int err;

        /*
         * This PDE acts only as an anchor for /proc/${pid}/net hierarchy.
         * Corresponding inode (PDE(inode) == net->proc_net) is never
         * instantiated therefore blanket zeroing is fine.
         * net->proc_net_stat inode is instantiated normally.
         */
        err = -ENOMEM;
        netd = kmem_cache_zalloc(proc_dir_entry_cache, GFP_KERNEL);
        if (!netd)
                goto out;

        netd->subdir = RB_ROOT;
        netd->data = net;
        netd->nlink = 2;
        netd->namelen = 3;
        netd->parent = &proc_root;
        netd->name = netd->inline_name;
        memcpy(netd->name, "net", 4);

        uid = make_kuid(net->user_ns, 0);
        if (!uid_valid(uid))
                uid = netd->uid;

        gid = make_kgid(net->user_ns, 0);
        if (!gid_valid(gid))
                gid = netd->gid;

        proc_set_user(netd, uid, gid);

        /* Seed dentry revalidation for /proc/${pid}/net */
        pde_force_lookup(netd);

        err = -EEXIST;
        net_statd = proc_net_mkdir(net, "stat", netd);
        if (!net_statd)
                goto free_net;

        net->proc_net = netd;
        net->proc_net_stat = net_statd;
        return 0;

free_net:
        pde_free(netd);
out:
        return err;
}

static __net_exit void proc_net_ns_exit(struct net *net)
{
        remove_proc_entry("stat", net->proc_net);
        pde_free(net->proc_net);
}

static struct pernet_operations __net_initdata proc_net_ns_ops = {
        .init = proc_net_ns_init,
        .exit = proc_net_ns_exit,
};

int __init proc_net_init(void)
{
        proc_symlink("net", NULL, "self/net");

        return register_pernet_subsys(&proc_net_ns_ops);
}