net/bpfilter/bpfilter_kern.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
   3 #include <linux/init.h>
   4 #include <linux/module.h>
   5 #include <linux/umh.h>
   6 #include <linux/bpfilter.h>
   7 #include <linux/sched.h>
   8 #include <linux/sched/signal.h>
   9 #include <linux/fs.h>
  10 #include <linux/file.h>
  11 #include "msgfmt.h"
  12
  13 extern char bpfilter_umh_start;
  14 extern char bpfilter_umh_end;
  15
  16 static struct umh_info info;
  17 /* since ip_getsockopt() can run in parallel, serialize access to umh */
  18 static DEFINE_MUTEX(bpfilter_lock);
  19
  20 static void shutdown_umh(struct umh_info *info)
  21 {
  22         struct task_struct *tsk;
  23
  24         if (!info->pid)
  25                 return;
  26         tsk = pid_task(find_vpid(info->pid), PIDTYPE_PID);
  27         if (tsk)
  28                 force_sig(SIGKILL, tsk);
  29         fput(info->pipe_to_umh);
  30         fput(info->pipe_from_umh);
  31         info->pid = 0;
  32 }
  33
  34 static void __stop_umh(void)
  35 {
  36         if (IS_ENABLED(CONFIG_INET)) {
  37                 bpfilter_process_sockopt = NULL;
  38                 shutdown_umh(&info);
  39         }
  40 }
  41
  42 static void stop_umh(void)
  43 {
  44         mutex_lock(&bpfilter_lock);
  45         __stop_umh();
  46         mutex_unlock(&bpfilter_lock);
  47 }
  48
  49 static int __bpfilter_process_sockopt(struct sock *sk, int optname,
  50                                       char __user *optval,
  51                                       unsigned int optlen, bool is_set)
  52 {
  53         struct mbox_request req;
  54         struct mbox_reply reply;
  55         loff_t pos;
  56         ssize_t n;
  57         int ret = -EFAULT;
  58
  59         req.is_set = is_set;
  60         req.pid = current->pid;
  61         req.cmd = optname;
  62         req.addr = (long)optval;
  63         req.len = optlen;
  64         mutex_lock(&bpfilter_lock);
  65         if (!info.pid)
  66                 goto out;
  67         n = __kernel_write(info.pipe_to_umh, &req, sizeof(req), &pos);
  68         if (n != sizeof(req)) {
  69                 pr_err("write fail %zd\n", n);
  70                 __stop_umh();
  71                 ret = -EFAULT;
  72                 goto out;
  73         }
  74         pos = 0;
  75         n = kernel_read(info.pipe_from_umh, &reply, sizeof(reply), &pos);
  76         if (n != sizeof(reply)) {
  77                 pr_err("read fail %zd\n", n);
  78                 __stop_umh();
  79                 ret = -EFAULT;
  80                 goto out;
  81         }
  82         ret = reply.status;
  83 out:
  84         mutex_unlock(&bpfilter_lock);
  85         return ret;
  86 }
  87
  88 static int __init load_umh(void)
  89 {
  90         int err;
  91
  92         /* fork usermode process */
  93         err = fork_usermode_blob(&bpfilter_umh_start,
  94                                  &bpfilter_umh_end - &bpfilter_umh_start,
  95                                  &info);
  96         if (err)
  97                 return err;
  98         pr_info("Loaded bpfilter_umh pid %d\n", info.pid);
  99
 100         /* health check that usermode process started correctly */
 101         if (__bpfilter_process_sockopt(NULL, 0, 0, 0, 0) != 0) {
 102                 stop_umh();
 103                 return -EFAULT;
 104         }
 105         if (IS_ENABLED(CONFIG_INET))
 106                 bpfilter_process_sockopt = &__bpfilter_process_sockopt;
 107
 108         return 0;
 109 }
 110
 111 static void __exit fini_umh(void)
 112 {
 113         stop_umh();
 114 }
 115 module_init(load_umh);
 116 module_exit(fini_umh);
 117 MODULE_LICENSE("GPL");