path: root/kernel/kmod.c

#include <linux/module.h>
#include <linux/sched.h>
#include <linux/syscalls.h>
#include <linux/unistd.h>
#include <linux/kmod.h>
#include <linux/slab.h>
#include <linux/completion.h>
#include <linux/cred.h>
#include <linux/file.h>
#include <linux/fdtable.h>
#include <linux/workqueue.h>
#include <linux/security.h>
#include <linux/mount.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/resource.h>
#include <linux/notifier.h>
#include <linux/suspend.h>
#include <linux/rwsem.h>
#include <asm/uaccess.h>

#include <trace/events/module.h>

extern int max_threads;

static struct workqueue_struct *khelper_wq;

#define CAP_BSET	(void *)1
#define CAP_PI		(void *)2

static kernel_cap_t usermodehelper_bset = CAP_FULL_SET;
static kernel_cap_t usermodehelper_inheritable = CAP_FULL_SET;
static DEFINE_SPINLOCK(umh_sysctl_lock);
static DECLARE_RWSEM(umhelper_sem);

#ifdef CONFIG_MODULES

char modprobe_path[KMOD_PATH_LEN] = "/sbin/modprobe";

static void free_modprobe_argv(struct subprocess_info *info)
{
	kfree(info->argv[3]); 
	kfree(info->argv);
}

static int call_modprobe(char *module_name, int wait)
{
	static char *envp[] = {
		"HOME=/",
		"TERM=linux",
		"PATH=/sbin:/usr/sbin:/bin:/usr/bin",
		NULL
	};

	char **argv = kmalloc(sizeof(char *[5]), GFP_KERNEL);
	if (!argv)
		goto out;

	module_name = kstrdup(module_name, GFP_KERNEL);
	if (!module_name)
		goto free_argv;

	argv[0] = modprobe_path;
	argv[1] = "-q";
	argv[2] = "--";
	argv[3] = module_name;	
	argv[4] = NULL;

	return call_usermodehelper_fns(modprobe_path, argv, envp,
		wait | UMH_KILLABLE, NULL, free_modprobe_argv, NULL);
free_argv:
	kfree(argv);
out:
	return -ENOMEM;
}

int __request_module(bool wait, const char *fmt, ...)
{
	va_list args;
	char module_name[MODULE_NAME_LEN];
	unsigned int max_modprobes;
	int ret;
	static atomic_t kmod_concurrent = ATOMIC_INIT(0);
#define MAX_KMOD_CONCURRENT 50	
	static int kmod_loop_msg;

	va_start(args, fmt);
	ret = vsnprintf(module_name, MODULE_NAME_LEN, fmt, args);
	va_end(args);
	if (ret >= MODULE_NAME_LEN)
		return -ENAMETOOLONG;

	ret = security_kernel_module_request(module_name);
	if (ret)
		return ret;

	max_modprobes = min(max_threads/2, MAX_KMOD_CONCURRENT);
	atomic_inc(&kmod_concurrent);
	if (atomic_read(&kmod_concurrent) > max_modprobes) {
		
		if (kmod_loop_msg < 5) {
			printk(KERN_ERR
			       "request_module: runaway loop modprobe %s\n",
			       module_name);
			kmod_loop_msg++;
		}
		atomic_dec(&kmod_concurrent);
		return -ENOMEM;
	}

	trace_module_request(module_name, wait, _RET_IP_);

	ret = call_modprobe(module_name, wait ? UMH_WAIT_PROC : UMH_WAIT_EXEC);

	atomic_dec(&kmod_concurrent);
	return ret;
}
EXPORT_SYMBOL(__request_module);
#endif 

static int ____call_usermodehelper(void *data)
{
	struct subprocess_info *sub_info = data;
	struct cred *new;
	int retval;

	spin_lock_irq(&current->sighand->siglock);
	flush_signal_handlers(current, 1);
	spin_unlock_irq(&current->sighand->siglock);

	
	set_cpus_allowed_ptr(current, cpu_all_mask);

	set_user_nice(current, 0);

	retval = -ENOMEM;
	new = prepare_kernel_cred(current);
	if (!new)
		goto fail;

	spin_lock(&umh_sysctl_lock);
	new->cap_bset = cap_intersect(usermodehelper_bset, new->cap_bset);
	new->cap_inheritable = cap_intersect(usermodehelper_inheritable,
					     new->cap_inheritable);
	spin_unlock(&umh_sysctl_lock);

	if (sub_info->init) {
		retval = sub_info->init(sub_info, new);
		if (retval) {
			abort_creds(new);
			goto fail;
		}
	}

	commit_creds(new);

	retval = kernel_execve(sub_info->path,
			       (const char *const *)sub_info->argv,
			       (const char *const *)sub_info->envp);

	
fail:
	sub_info->retval = retval;
	return 0;
}

void call_usermodehelper_freeinfo(struct subprocess_info *info)
{
	if (info->cleanup)
		(*info->cleanup)(info);
	kfree(info);
}
EXPORT_SYMBOL(call_usermodehelper_freeinfo);

static void umh_complete(struct subprocess_info *sub_info)
{
	struct completion *comp = xchg(&sub_info->complete, NULL);
	if (comp)
		complete(comp);
	else
		call_usermodehelper_freeinfo(sub_info);
}

static int wait_for_helper(void *data)
{
	struct subprocess_info *sub_info = data;
	pid_t pid;

	
	spin_lock_irq(&current->sighand->siglock);
	current->sighand->action[SIGCHLD-1].sa.sa_handler = SIG_DFL;
	spin_unlock_irq(&current->sighand->siglock);

	pid = kernel_thread(____call_usermodehelper, sub_info, SIGCHLD);
	if (pid < 0) {
		sub_info->retval = pid;
	} else {
		int ret = -ECHILD;
		sys_wait4(pid, (int __user *)&ret, 0, NULL);

		if (ret)
			sub_info->retval = ret;
	}

	umh_complete(sub_info);
	return 0;
}

static void __call_usermodehelper(struct work_struct *work)
{
	struct subprocess_info *sub_info =
		container_of(work, struct subprocess_info, work);
	int wait = sub_info->wait & ~UMH_KILLABLE;
	pid_t pid;

	if (wait == UMH_WAIT_PROC)
		pid = kernel_thread(wait_for_helper, sub_info,
				    CLONE_FS | CLONE_FILES | SIGCHLD);
	else
		pid = kernel_thread(____call_usermodehelper, sub_info,
				    CLONE_VFORK | SIGCHLD);

	switch (wait) {
	case UMH_NO_WAIT:
		call_usermodehelper_freeinfo(sub_info);
		break;

	case UMH_WAIT_PROC:
		if (pid > 0)
			break;
		
	case UMH_WAIT_EXEC:
		if (pid < 0)
			sub_info->retval = pid;
		umh_complete(sub_info);
	}
}

static enum umh_disable_depth usermodehelper_disabled = UMH_DISABLED;

static atomic_t running_helpers = ATOMIC_INIT(0);

static DECLARE_WAIT_QUEUE_HEAD(running_helpers_waitq);

static DECLARE_WAIT_QUEUE_HEAD(usermodehelper_disabled_waitq);

#define RUNNING_HELPERS_TIMEOUT	(5 * HZ)

int usermodehelper_read_trylock(void)
{
	DEFINE_WAIT(wait);
	int ret = 0;

	down_read(&umhelper_sem);
	for (;;) {
		prepare_to_wait(&usermodehelper_disabled_waitq, &wait,
				TASK_INTERRUPTIBLE);
		if (!usermodehelper_disabled)
			break;

		if (usermodehelper_disabled == UMH_DISABLED)
			ret = -EAGAIN;

		up_read(&umhelper_sem);

		if (ret)
			break;

		schedule();
		try_to_freeze();

		down_read(&umhelper_sem);
	}
	finish_wait(&usermodehelper_disabled_waitq, &wait);
	return ret;
}
EXPORT_SYMBOL_GPL(usermodehelper_read_trylock);

long usermodehelper_read_lock_wait(long timeout)
{
	DEFINE_WAIT(wait);

	if (timeout < 0)
		return -EINVAL;

	down_read(&umhelper_sem);
	for (;;) {
		prepare_to_wait(&usermodehelper_disabled_waitq, &wait,
				TASK_UNINTERRUPTIBLE);
		if (!usermodehelper_disabled)
			break;

		up_read(&umhelper_sem);

		timeout = schedule_timeout(timeout);
		if (!timeout)
			break;

		down_read(&umhelper_sem);
	}
	finish_wait(&usermodehelper_disabled_waitq, &wait);
	return timeout;
}
EXPORT_SYMBOL_GPL(usermodehelper_read_lock_wait);

void usermodehelper_read_unlock(void)
{
	up_read(&umhelper_sem);
}
EXPORT_SYMBOL_GPL(usermodehelper_read_unlock);

void __usermodehelper_set_disable_depth(enum umh_disable_depth depth)
{
	down_write(&umhelper_sem);
	usermodehelper_disabled = depth;
	wake_up(&usermodehelper_disabled_waitq);
	up_write(&umhelper_sem);
}

int __usermodehelper_disable(enum umh_disable_depth depth)
{
	long retval;

	if (!depth)
		return -EINVAL;

	down_write(&umhelper_sem);
	usermodehelper_disabled = depth;
	up_write(&umhelper_sem);

	retval = wait_event_timeout(running_helpers_waitq,
					atomic_read(&running_helpers) == 0,
					RUNNING_HELPERS_TIMEOUT);
	if (retval)
		return 0;

	__usermodehelper_set_disable_depth(UMH_ENABLED);
	return -EAGAIN;
}

static void helper_lock(void)
{
	atomic_inc(&running_helpers);
	smp_mb__after_atomic_inc();
}

static void helper_unlock(void)
{
	if (atomic_dec_and_test(&running_helpers))
		wake_up(&running_helpers_waitq);
}

struct subprocess_info *call_usermodehelper_setup(char *path, char **argv,
						  char **envp, gfp_t gfp_mask)
{
	struct subprocess_info *sub_info;
	sub_info = kzalloc(sizeof(struct subprocess_info), gfp_mask);
	if (!sub_info)
		goto out;

	INIT_WORK(&sub_info->work, __call_usermodehelper);
	sub_info->path = path;
	sub_info->argv = argv;
	sub_info->envp = envp;
  out:
	return sub_info;
}
EXPORT_SYMBOL(call_usermodehelper_setup);

void call_usermodehelper_setfns(struct subprocess_info *info,
		    int (*init)(struct subprocess_info *info, struct cred *new),
		    void (*cleanup)(struct subprocess_info *info),
		    void *data)
{
	info->cleanup = cleanup;
	info->init = init;
	info->data = data;
}
EXPORT_SYMBOL(call_usermodehelper_setfns);

int call_usermodehelper_exec(struct subprocess_info *sub_info, int wait)
{
	DECLARE_COMPLETION_ONSTACK(done);
	int retval = 0;

	helper_lock();
	if (sub_info->path[0] == '\0')
		goto out;

	if (!khelper_wq || usermodehelper_disabled) {
		retval = -EBUSY;
		goto out;
	}

	sub_info->complete = &done;
	sub_info->wait = wait;

	queue_work(khelper_wq, &sub_info->work);
	if (wait == UMH_NO_WAIT)	
		goto unlock;

	if (wait & UMH_KILLABLE) {
		retval = wait_for_completion_killable(&done);
		if (!retval)
			goto wait_done;

		
		if (xchg(&sub_info->complete, NULL))
			goto unlock;
		
	}

	wait_for_completion(&done);
wait_done:
	retval = sub_info->retval;
out:
	call_usermodehelper_freeinfo(sub_info);
unlock:
	helper_unlock();
	return retval;
}
EXPORT_SYMBOL(call_usermodehelper_exec);

static int proc_cap_handler(struct ctl_table *table, int write,
			 void __user *buffer, size_t *lenp, loff_t *ppos)
{
	struct ctl_table t;
	unsigned long cap_array[_KERNEL_CAPABILITY_U32S];
	kernel_cap_t new_cap;
	int err, i;

	if (write && (!capable(CAP_SETPCAP) ||
		      !capable(CAP_SYS_MODULE)))
		return -EPERM;

	spin_lock(&umh_sysctl_lock);
	for (i = 0; i < _KERNEL_CAPABILITY_U32S; i++)  {
		if (table->data == CAP_BSET)
			cap_array[i] = usermodehelper_bset.cap[i];
		else if (table->data == CAP_PI)
			cap_array[i] = usermodehelper_inheritable.cap[i];
		else
			BUG();
	}
	spin_unlock(&umh_sysctl_lock);

	t = *table;
	t.data = &cap_array;

	err = proc_doulongvec_minmax(&t, write, buffer, lenp, ppos);
	if (err < 0)
		return err;

	for (i = 0; i < _KERNEL_CAPABILITY_U32S; i++)
		new_cap.cap[i] = cap_array[i];

	spin_lock(&umh_sysctl_lock);
	if (write) {
		if (table->data == CAP_BSET)
			usermodehelper_bset = cap_intersect(usermodehelper_bset, new_cap);
		if (table->data == CAP_PI)
			usermodehelper_inheritable = cap_intersect(usermodehelper_inheritable, new_cap);
	}
	spin_unlock(&umh_sysctl_lock);

	return 0;
}

struct ctl_table usermodehelper_table[] = {
	{
		.procname	= "bset",
		.data		= CAP_BSET,
		.maxlen		= _KERNEL_CAPABILITY_U32S * sizeof(unsigned long),
		.mode		= 0600,
		.proc_handler	= proc_cap_handler,
	},
	{
		.procname	= "inheritable",
		.data		= CAP_PI,
		.maxlen		= _KERNEL_CAPABILITY_U32S * sizeof(unsigned long),
		.mode		= 0600,
		.proc_handler	= proc_cap_handler,
	},
	{ }
};

void __init usermodehelper_init(void)
{
	khelper_wq = create_singlethread_workqueue("khelper");
	BUG_ON(!khelper_wq);
}