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// SPDX-License-Identifier: GPL-2.0
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/init.h>
#include <linux/module.h>
#include <linux/umh.h>
#include <linux/bpfilter.h>
#include <linux/sched.h>
#include <linux/sched/signal.h>
#include <linux/fs.h>
#include <linux/file.h>
#include "msgfmt.h"
extern char bpfilter_umh_start;
extern char bpfilter_umh_end;
static struct umh_info info;
/* since ip_getsockopt() can run in parallel, serialize access to umh */
static DEFINE_MUTEX(bpfilter_lock);
static void shutdown_umh(struct umh_info *info)
{
struct task_struct *tsk;
if (!info->pid)
return;
tsk = get_pid_task(find_vpid(info->pid), PIDTYPE_PID);
if (tsk) {
force_sig(SIGKILL, tsk);
put_task_struct(tsk);
}
fput(info->pipe_to_umh);
fput(info->pipe_from_umh);
info->pid = 0;
}
static void __stop_umh(void)
{
if (IS_ENABLED(CONFIG_INET)) {
bpfilter_process_sockopt = NULL;
shutdown_umh(&info);
}
}
static void stop_umh(void)
{
mutex_lock(&bpfilter_lock);
__stop_umh();
mutex_unlock(&bpfilter_lock);
}
static int __bpfilter_process_sockopt(struct sock *sk, int optname,
char __user *optval,
unsigned int optlen, bool is_set)
{
struct mbox_request req;
struct mbox_reply reply;
loff_t pos;
ssize_t n;
int ret = -EFAULT;
req.is_set = is_set;
req.pid = current->pid;
req.cmd = optname;
req.addr = (long __force __user)optval;
req.len = optlen;
mutex_lock(&bpfilter_lock);
if (!info.pid)
goto out;
n = __kernel_write(info.pipe_to_umh, &req, sizeof(req), &pos);
if (n != sizeof(req)) {
pr_err("write fail %zd\n", n);
__stop_umh();
ret = -EFAULT;
goto out;
}
pos = 0;
n = kernel_read(info.pipe_from_umh, &reply, sizeof(reply), &pos);
if (n != sizeof(reply)) {
pr_err("read fail %zd\n", n);
__stop_umh();
ret = -EFAULT;
goto out;
}
ret = reply.status;
out:
mutex_unlock(&bpfilter_lock);
return ret;
}
static int __init load_umh(void)
{
int err;
/* fork usermode process */
info.cmdline = "bpfilter_umh";
err = fork_usermode_blob(&bpfilter_umh_start,
&bpfilter_umh_end - &bpfilter_umh_start,
&info);
if (err)
return err;
pr_info("Loaded bpfilter_umh pid %d\n", info.pid);
/* health check that usermode process started correctly */
if (__bpfilter_process_sockopt(NULL, 0, NULL, 0, 0) != 0) {
stop_umh();
return -EFAULT;
}
if (IS_ENABLED(CONFIG_INET))
bpfilter_process_sockopt = &__bpfilter_process_sockopt;
return 0;
}
static void __exit fini_umh(void)
{
stop_umh();
}
module_init(load_umh);
module_exit(fini_umh);
MODULE_LICENSE("GPL");
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