// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * cn_proc.c - process events connector
 *
 * Copyright (C) Matt Helsley, IBM Corp. 2005
 * Based on cn_fork.c by Guillaume Thouvenin <guillaume.thouvenin@bull.net>
 * Original copyright notice follows:
 * Copyright (C) 2005 BULL SA.
 */

#include <linux/kernel.h>
#include <linux/ktime.h>
#include <linux/init.h>
#include <linux/connector.h>
#include <linux/gfp.h>
#include <linux/ptrace.h>
#include <linux/atomic.h>
#include <linux/pid_namespace.h>

#include <linux/cn_proc.h>
#include <linux/local_lock.h>

/*
 * Size of a cn_msg followed by a proc_event structure.  Since the
 * sizeof struct cn_msg is a multiple of 4 bytes, but not 8 bytes, we
 * add one 4-byte word to the size here, and then start the actual
 * cn_msg structure 4 bytes into the stack buffer.  The result is that
 * the immediately following proc_event structure is aligned to 8 bytes.
 */
#define CN_PROC_MSG_SIZE (sizeof(struct cn_msg) + sizeof(struct proc_event) + 4)

/* See comment above; we test our assumption about sizeof struct cn_msg here. */
static inline struct cn_msg *buffer_to_cn_msg(__u8 *buffer)
{
        BUILD_BUG_ON(sizeof(struct cn_msg) != 20);
        return (struct cn_msg *)(buffer + 4);
}

static atomic_t proc_event_num_listeners = ATOMIC_INIT(0);
static struct cb_id cn_proc_event_id = { CN_IDX_PROC, CN_VAL_PROC };

/* local_event.count is used as the sequence number of the netlink message */
struct local_event {
        local_lock_t lock;
        __u32 count;
};
static DEFINE_PER_CPU(struct local_event, local_event) = {
        .lock = INIT_LOCAL_LOCK(lock),
};

static int cn_filter(struct sock *dsk, struct sk_buff *skb, void *data)
{
        __u32 what, exit_code, *ptr;
        enum proc_cn_mcast_op mc_op;
        uintptr_t val;

        if (!dsk || !dsk->sk_user_data || !data)
                return 0;

        ptr = (__u32 *)data;
        what = *ptr++;
        exit_code = *ptr;
        val = ((struct proc_input *)(dsk->sk_user_data))->event_type;
        mc_op = ((struct proc_input *)(dsk->sk_user_data))->mcast_op;

        if (mc_op == PROC_CN_MCAST_IGNORE)
                return 1;

        if ((__u32)val == PROC_EVENT_ALL)
                return 0;

        /*
         * Drop packet if we have to report only non-zero exit status
         * (PROC_EVENT_NONZERO_EXIT) and exit status is 0
         */
        if (((__u32)val & PROC_EVENT_NONZERO_EXIT) &&
            (what == PROC_EVENT_EXIT)) {
                if (exit_code)
                        return 0;
        }

        if ((__u32)val & what)
                return 0;

        return 1;
}

static inline void send_msg(struct cn_msg *msg)
{
        __u32 filter_data[2];

        local_lock(&local_event.lock);

        msg->seq = __this_cpu_inc_return(local_event.count) - 1;
        ((struct proc_event *)msg->data)->cpu = smp_processor_id();

        /*
         * local_lock() disables preemption during send to ensure the messages
         * are ordered according to their sequence numbers.
         *
         * If cn_netlink_send() fails, the data is not sent.
         */
        filter_data[0] = ((struct proc_event *)msg->data)->what;
        if (filter_data[0] == PROC_EVENT_EXIT) {
                filter_data[1] =
                ((struct proc_event *)msg->data)->event_data.exit.exit_code;
        } else {
                filter_data[1] = 0;
        }

        cn_netlink_send_mult(msg, msg->len, 0, CN_IDX_PROC, GFP_NOWAIT,
                             cn_filter, (void *)filter_data);

        local_unlock(&local_event.lock);
}

void proc_fork_connector(struct task_struct *task)
{
        struct cn_msg *msg;
        struct proc_event *ev;
        __u8 buffer[CN_PROC_MSG_SIZE] __aligned(8);
        struct task_struct *parent;

        if (atomic_read(&proc_event_num_listeners) < 1)
                return;

        msg = buffer_to_cn_msg(buffer);
        ev = (struct proc_event *)msg->data;
        memset(&ev->event_data, 0, sizeof(ev->event_data));
        ev->timestamp_ns = ktime_get_ns();
        ev->what = PROC_EVENT_FORK;
        rcu_read_lock();
        parent = rcu_dereference(task->real_parent);
        ev->event_data.fork.parent_pid = parent->pid;
        ev->event_data.fork.parent_tgid = parent->tgid;
        rcu_read_unlock();
        ev->event_data.fork.child_pid = task->pid;
        ev->event_data.fork.child_tgid = task->tgid;

        memcpy(&msg->id, &cn_proc_event_id, sizeof(msg->id));
        msg->ack = 0; /* not used */
        msg->len = sizeof(*ev);
        msg->flags = 0; /* not used */
        send_msg(msg);
}

void proc_exec_connector(struct task_struct *task)
{
        struct cn_msg *msg;
        struct proc_event *ev;
        __u8 buffer[CN_PROC_MSG_SIZE] __aligned(8);

        if (atomic_read(&proc_event_num_listeners) < 1)
                return;

        msg = buffer_to_cn_msg(buffer);
        ev = (struct proc_event *)msg->data;
        memset(&ev->event_data, 0, sizeof(ev->event_data));
        ev->timestamp_ns = ktime_get_ns();
        ev->what = PROC_EVENT_EXEC;
        ev->event_data.exec.process_pid = task->pid;
        ev->event_data.exec.process_tgid = task->tgid;

        memcpy(&msg->id, &cn_proc_event_id, sizeof(msg->id));
        msg->ack = 0; /* not used */
        msg->len = sizeof(*ev);
        msg->flags = 0; /* not used */
        send_msg(msg);
}

void proc_id_connector(struct task_struct *task, int which_id)
{
        struct cn_msg *msg;
        struct proc_event *ev;
        __u8 buffer[CN_PROC_MSG_SIZE] __aligned(8);
        const struct cred *cred;

        if (atomic_read(&proc_event_num_listeners) < 1)
                return;

        msg = buffer_to_cn_msg(buffer);
        ev = (struct proc_event *)msg->data;
        memset(&ev->event_data, 0, sizeof(ev->event_data));
        ev->what = which_id;
        ev->event_data.id.process_pid = task->pid;
        ev->event_data.id.process_tgid = task->tgid;
        rcu_read_lock();
        cred = __task_cred(task);
        if (which_id == PROC_EVENT_UID) {
                ev->event_data.id.r.ruid = from_kuid_munged(&init_user_ns, cred->uid);
                ev->event_data.id.e.euid = from_kuid_munged(&init_user_ns, cred->euid);
        } else if (which_id == PROC_EVENT_GID) {
                ev->event_data.id.r.rgid = from_kgid_munged(&init_user_ns, cred->gid);
                ev->event_data.id.e.egid = from_kgid_munged(&init_user_ns, cred->egid);
        } else {
                rcu_read_unlock();
                return;
        }
        rcu_read_unlock();
        ev->timestamp_ns = ktime_get_ns();

        memcpy(&msg->id, &cn_proc_event_id, sizeof(msg->id));
        msg->ack = 0; /* not used */
        msg->len = sizeof(*ev);
        msg->flags = 0; /* not used */
        send_msg(msg);
}

void proc_sid_connector(struct task_struct *task)
{
        struct cn_msg *msg;
        struct proc_event *ev;
        __u8 buffer[CN_PROC_MSG_SIZE] __aligned(8);

        if (atomic_read(&proc_event_num_listeners) < 1)
                return;

        msg = buffer_to_cn_msg(buffer);
        ev = (struct proc_event *)msg->data;
        memset(&ev->event_data, 0, sizeof(ev->event_data));
        ev->timestamp_ns = ktime_get_ns();
        ev->what = PROC_EVENT_SID;
        ev->event_data.sid.process_pid = task->pid;
        ev->event_data.sid.process_tgid = task->tgid;

        memcpy(&msg->id, &cn_proc_event_id, sizeof(msg->id));
        msg->ack = 0; /* not used */
        msg->len = sizeof(*ev);
        msg->flags = 0; /* not used */
        send_msg(msg);
}

void proc_ptrace_connector(struct task_struct *task, int ptrace_id)
{
        struct cn_msg *msg;
        struct proc_event *ev;
        __u8 buffer[CN_PROC_MSG_SIZE] __aligned(8);

        if (atomic_read(&proc_event_num_listeners) < 1)
                return;

        msg = buffer_to_cn_msg(buffer);
        ev = (struct proc_event *)msg->data;
        memset(&ev->event_data, 0, sizeof(ev->event_data));
        ev->timestamp_ns = ktime_get_ns();
        ev->what = PROC_EVENT_PTRACE;
        ev->event_data.ptrace.process_pid  = task->pid;
        ev->event_data.ptrace.process_tgid = task->tgid;
        if (ptrace_id == PTRACE_ATTACH) {
                ev->event_data.ptrace.tracer_pid  = current->pid;
                ev->event_data.ptrace.tracer_tgid = current->tgid;
        } else if (ptrace_id == PTRACE_DETACH) {
                ev->event_data.ptrace.tracer_pid  = 0;
                ev->event_data.ptrace.tracer_tgid = 0;
        } else
                return;

        memcpy(&msg->id, &cn_proc_event_id, sizeof(msg->id));
        msg->ack = 0; /* not used */
        msg->len = sizeof(*ev);
        msg->flags = 0; /* not used */
        send_msg(msg);
}

void proc_comm_connector(struct task_struct *task)
{
        struct cn_msg *msg;
        struct proc_event *ev;
        __u8 buffer[CN_PROC_MSG_SIZE] __aligned(8);

        if (atomic_read(&proc_event_num_listeners) < 1)
                return;

        msg = buffer_to_cn_msg(buffer);
        ev = (struct proc_event *)msg->data;
        memset(&ev->event_data, 0, sizeof(ev->event_data));
        ev->timestamp_ns = ktime_get_ns();
        ev->what = PROC_EVENT_COMM;
        ev->event_data.comm.process_pid  = task->pid;
        ev->event_data.comm.process_tgid = task->tgid;
        get_task_comm(ev->event_data.comm.comm, task);

        memcpy(&msg->id, &cn_proc_event_id, sizeof(msg->id));
        msg->ack = 0; /* not used */
        msg->len = sizeof(*ev);
        msg->flags = 0; /* not used */
        send_msg(msg);
}

void proc_coredump_connector(struct task_struct *task)
{
        struct cn_msg *msg;
        struct proc_event *ev;
        struct task_struct *parent;
        __u8 buffer[CN_PROC_MSG_SIZE] __aligned(8);

        if (atomic_read(&proc_event_num_listeners) < 1)
                return;

        msg = buffer_to_cn_msg(buffer);
        ev = (struct proc_event *)msg->data;
        memset(&ev->event_data, 0, sizeof(ev->event_data));
        ev->timestamp_ns = ktime_get_ns();
        ev->what = PROC_EVENT_COREDUMP;
        ev->event_data.coredump.process_pid = task->pid;
        ev->event_data.coredump.process_tgid = task->tgid;

        rcu_read_lock();
        if (pid_alive(task)) {
                parent = rcu_dereference(task->real_parent);
                ev->event_data.coredump.parent_pid = parent->pid;
                ev->event_data.coredump.parent_tgid = parent->tgid;
        }
        rcu_read_unlock();

        memcpy(&msg->id, &cn_proc_event_id, sizeof(msg->id));
        msg->ack = 0; /* not used */
        msg->len = sizeof(*ev);
        msg->flags = 0; /* not used */
        send_msg(msg);
}

void proc_exit_connector(struct task_struct *task)
{
        struct cn_msg *msg;
        struct proc_event *ev;
        struct task_struct *parent;
        __u8 buffer[CN_PROC_MSG_SIZE] __aligned(8);

        if (atomic_read(&proc_event_num_listeners) < 1)
                return;

        msg = buffer_to_cn_msg(buffer);
        ev = (struct proc_event *)msg->data;
        memset(&ev->event_data, 0, sizeof(ev->event_data));
        ev->timestamp_ns = ktime_get_ns();
        ev->what = PROC_EVENT_EXIT;
        ev->event_data.exit.process_pid = task->pid;
        ev->event_data.exit.process_tgid = task->tgid;
        ev->event_data.exit.exit_code = task->exit_code;
        ev->event_data.exit.exit_signal = task->exit_signal;

        rcu_read_lock();
        if (pid_alive(task)) {
                parent = rcu_dereference(task->real_parent);
                ev->event_data.exit.parent_pid = parent->pid;
                ev->event_data.exit.parent_tgid = parent->tgid;
        }
        rcu_read_unlock();

        memcpy(&msg->id, &cn_proc_event_id, sizeof(msg->id));
        msg->ack = 0; /* not used */
        msg->len = sizeof(*ev);
        msg->flags = 0; /* not used */
        send_msg(msg);
}

/*
 * Send an acknowledgement message to userspace
 *
 * Use 0 for success, EFOO otherwise.
 * Note: this is the negative of conventional kernel error
 * values because it's not being returned via syscall return
 * mechanisms.
 */
static void cn_proc_ack(int err, int rcvd_seq, int rcvd_ack)
{
        struct cn_msg *msg;
        struct proc_event *ev;
        __u8 buffer[CN_PROC_MSG_SIZE] __aligned(8);

        if (atomic_read(&proc_event_num_listeners) < 1)
                return;

        msg = buffer_to_cn_msg(buffer);
        ev = (struct proc_event *)msg->data;
        memset(&ev->event_data, 0, sizeof(ev->event_data));
        msg->seq = rcvd_seq;
        ev->timestamp_ns = ktime_get_ns();
        ev->cpu = -1;
        ev->what = PROC_EVENT_NONE;
        ev->event_data.ack.err = err;
        memcpy(&msg->id, &cn_proc_event_id, sizeof(msg->id));
        msg->ack = rcvd_ack + 1;
        msg->len = sizeof(*ev);
        msg->flags = 0; /* not used */
        send_msg(msg);
}

/**
 * cn_proc_mcast_ctl
 * @msg: message sent from userspace via the connector
 * @nsp: NETLINK_CB of the client's socket buffer
 */
static void cn_proc_mcast_ctl(struct cn_msg *msg,
                              struct netlink_skb_parms *nsp)
{
        enum proc_cn_mcast_op mc_op = 0, prev_mc_op = 0;
        struct proc_input *pinput = NULL;
        enum proc_cn_event ev_type = 0;
        int err = 0, initial = 0;
        struct sock *sk = NULL;

        /* 
         * Events are reported with respect to the initial pid
         * and user namespaces so ignore requestors from
         * other namespaces.
         */
        if ((current_user_ns() != &init_user_ns) ||
            !task_is_in_init_pid_ns(current))
                return;

        if (msg->len == sizeof(*pinput)) {
                pinput = (struct proc_input *)msg->data;
                mc_op = pinput->mcast_op;
                ev_type = pinput->event_type;
        } else if (msg->len == sizeof(mc_op)) {
                mc_op = *((enum proc_cn_mcast_op *)msg->data);
                ev_type = PROC_EVENT_ALL;
        } else {
                return;
        }

        ev_type = valid_event((enum proc_cn_event)ev_type);

        if (ev_type == PROC_EVENT_NONE)
                ev_type = PROC_EVENT_ALL;

        if (nsp->sk) {
                sk = nsp->sk;
                if (sk->sk_user_data == NULL) {
                        sk->sk_user_data = kzalloc_obj(struct proc_input);
                        if (sk->sk_user_data == NULL) {
                                err = ENOMEM;
                                goto out;
                        }
                        initial = 1;
                } else {
                        prev_mc_op =
                        ((struct proc_input *)(sk->sk_user_data))->mcast_op;
                }
                ((struct proc_input *)(sk->sk_user_data))->event_type =
                        ev_type;
                ((struct proc_input *)(sk->sk_user_data))->mcast_op = mc_op;
        }

        switch (mc_op) {
        case PROC_CN_MCAST_LISTEN:
                if (initial || (prev_mc_op != PROC_CN_MCAST_LISTEN))
                        atomic_inc(&proc_event_num_listeners);
                break;
        case PROC_CN_MCAST_IGNORE:
                if (!initial && (prev_mc_op != PROC_CN_MCAST_IGNORE))
                        atomic_dec(&proc_event_num_listeners);
                ((struct proc_input *)(sk->sk_user_data))->event_type =
                        PROC_EVENT_NONE;
                break;
        default:
                err = EINVAL;
                break;
        }

out:
        cn_proc_ack(err, msg->seq, msg->ack);
}

/*
 * cn_proc_init - initialization entry point
 *
 * Adds the connector callback to the connector driver.
 */
static int __init cn_proc_init(void)
{
        int err = cn_add_callback(&cn_proc_event_id,
                                  "cn_proc",
                                  &cn_proc_mcast_ctl);
        if (err) {
                pr_warn("cn_proc failed to register\n");
                return err;
        }
        return 0;
}
device_initcall(cn_proc_init);