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linux/drivers/connector/cn_proc.c
Anjali Kulkarni 743acf351b connector/cn_proc: Performance improvements 
This patch adds the capability to filter messages sent by the proc
connector on the event type supplied in the message from the client
to the connector. The client can register to listen for an event type
given in struct proc_input.

This event based filteting will greatly enhance performance - handling
8K exits takes about 70ms, whereas 8K-forks + 8K-exits takes about 150ms
& handling 8K-forks + 8K-exits + 8K-execs takes 200ms. There are currently
9 different types of events, and we need to listen to all of them. Also,
measuring the time using pidfds for monitoring 8K process exits took
much longer - 200ms, as compared to 70ms using only exit notifications of
proc connector.

We also add a new event type - PROC_EVENT_NONZERO_EXIT, which is
only sent by kernel to a listening application when any process exiting,
has a non-zero exit status. This will help the clients like Oracle DB,
where a monitoring process wants notfications for non-zero process exits
so it can cleanup after them.

This kind of a new event could also be useful to other applications like
Google's lmkd daemon, which needs a killed process's exit notification.

The patch takes care that existing clients using old mechanism of not
sending the event type work without any changes.

cn_filter function checks to see if the event type being notified via
proc connector matches the event type requested by client, before
sending(matches) or dropping(does not match) a packet.

Signed-off-by: Anjali Kulkarni <anjali.k.kulkarni@oracle.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2023-07-23 11:34:22 +01:00

491 lines
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// 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 || !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;
/* Can only change if privileged. */
if (!__netlink_ns_capable(nsp, &init_user_ns, CAP_NET_ADMIN)) {
err = EPERM;
goto out;
}
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(sizeof(struct proc_input),
GFP_KERNEL);
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);
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