[linux.git] / kernel / kmod.c

/*
	kmod, the new module loader (replaces kerneld)
	Kirk Petersen

	Reorganized not to be a daemon by Adam Richter, with guidance
	from Greg Zornetzer.

	Modified to avoid chroot and file sharing problems.
	Mikael Pettersson

	Limit the concurrent number of kmod modprobes to catch loops from
	"modprobe needs a service that is in a module".
	Keith Owens <[email protected]> December 1999

	Unblock all signals when we exec a usermode process.
	Shuu Yamaguchi <[email protected]> December 2000

	call_usermodehelper wait flag, and remove exec_usermodehelper.
	Rusty Russell <[email protected]>  Jan 2003
*/
#define __KERNEL_SYSCALLS__

#include <linux/module.h>
#include <linux/sched.h>
#include <linux/syscalls.h>
#include <linux/unistd.h>
#include <linux/kmod.h>
#include <linux/smp_lock.h>
#include <linux/slab.h>
#include <linux/namespace.h>
#include <linux/completion.h>
#include <linux/file.h>
#include <linux/workqueue.h>
#include <linux/security.h>
#include <linux/mount.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <asm/uaccess.h>

extern int max_threads;

static struct workqueue_struct *khelper_wq;

#ifdef CONFIG_KMOD

/*
	modprobe_path is set via /proc/sys.
*/
char modprobe_path[KMOD_PATH_LEN] = "/sbin/modprobe";

/**
 * request_module - try to load a kernel module
 * @fmt:     printf style format string for the name of the module
 * @varargs: arguements as specified in the format string
 *
 * Load a module using the user mode module loader. The function returns
 * zero on success or a negative errno code on failure. Note that a
 * successful module load does not mean the module did not then unload
 * and exit on an error of its own. Callers must check that the service
 * they requested is now available not blindly invoke it.
 *
 * If module auto-loading support is disabled then this function
 * becomes a no-operation.
 */
int request_module(const char *fmt, ...)
{
	va_list args;
	char module_name[MODULE_NAME_LEN];
	unsigned int max_modprobes;
	int ret;
	char *argv[] = { modprobe_path, "-q", "--", module_name, NULL };
	static char *envp[] = { "HOME=/",
				"TERM=linux",
				"PATH=/sbin:/usr/sbin:/bin:/usr/bin",
				NULL };
	static atomic_t kmod_concurrent = ATOMIC_INIT(0);
#define MAX_KMOD_CONCURRENT 50	/* Completely arbitrary value - KAO */
	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;

	/* If modprobe needs a service that is in a module, we get a recursive
	 * loop.  Limit the number of running kmod threads to max_threads/2 or
	 * MAX_KMOD_CONCURRENT, whichever is the smaller.  A cleaner method
	 * would be to run the parents of this process, counting how many times
	 * kmod was invoked.  That would mean accessing the internals of the
	 * process tables to get the command line, proc_pid_cmdline is static
	 * and it is not worth changing the proc code just to handle this case. 
	 * KAO.
	 *
	 * "trace the ppid" is simple, but will fail if someone's
	 * parent exits.  I think this is as good as it gets. --RR
	 */
	max_modprobes = min(max_threads/2, MAX_KMOD_CONCURRENT);
	atomic_inc(&kmod_concurrent);
	if (atomic_read(&kmod_concurrent) > max_modprobes) {
		/* We may be blaming an innocent here, but unlikely */
		if (kmod_loop_msg++ < 5)
			printk(KERN_ERR
			       "request_module: runaway loop modprobe %s\n",
			       module_name);
		atomic_dec(&kmod_concurrent);
		return -ENOMEM;
	}

	ret = call_usermodehelper(modprobe_path, argv, envp, 1);
	atomic_dec(&kmod_concurrent);
	return ret;
}
EXPORT_SYMBOL(request_module);
#endif /* CONFIG_KMOD */

struct subprocess_info {
	struct completion *complete;
	char *path;
	char **argv;
	char **envp;
	struct key *ring;
	int wait;
	int retval;
};

/*
 * This is the task which runs the usermode application
 */
static int ____call_usermodehelper(void *data)
{
	struct subprocess_info *sub_info = data;
	struct key *new_session, *old_session;
	int retval;

	/* Unblock all signals and set the session keyring. */
	new_session = key_get(sub_info->ring);
	flush_signals(current);
	spin_lock_irq(&current->sighand->siglock);
	old_session = __install_session_keyring(current, new_session);
	flush_signal_handlers(current, 1);
	sigemptyset(&current->blocked);
	recalc_sigpending();
	spin_unlock_irq(&current->sighand->siglock);

	key_put(old_session);

	/* We can run anywhere, unlike our parent keventd(). */
	set_cpus_allowed(current, CPU_MASK_ALL);

	retval = -EPERM;
	if (current->fs->root)
		retval = execve(sub_info->path, sub_info->argv,sub_info->envp);

	/* Exec failed? */
	sub_info->retval = retval;
	do_exit(0);
}

/* Keventd can't block, but this (a child) can. */
static int wait_for_helper(void *data)
{
	struct subprocess_info *sub_info = data;
	pid_t pid;
	struct k_sigaction sa;

	/* Install a handler: if SIGCLD isn't handled sys_wait4 won't
	 * populate the status, but will return -ECHILD. */
	sa.sa.sa_handler = SIG_IGN;
	sa.sa.sa_flags = 0;
	siginitset(&sa.sa.sa_mask, sigmask(SIGCHLD));
	do_sigaction(SIGCHLD, &sa, NULL);
	allow_signal(SIGCHLD);

	pid = kernel_thread(____call_usermodehelper, sub_info, SIGCHLD);
	if (pid < 0) {
		sub_info->retval = pid;
	} else {
		/*
		 * Normally it is bogus to call wait4() from in-kernel because
		 * wait4() wants to write the exit code to a userspace address.
		 * But wait_for_helper() always runs as keventd, and put_user()
		 * to a kernel address works OK for kernel threads, due to their
		 * having an mm_segment_t which spans the entire address space.
		 *
		 * Thus the __user pointer cast is valid here.
		 */
		sys_wait4(pid, (int __user *) &sub_info->retval, 0, NULL);
	}

	complete(sub_info->complete);
	return 0;
}

/* This is run by khelper thread  */
static void __call_usermodehelper(void *data)
{
	struct subprocess_info *sub_info = data;
	pid_t pid;
	int wait = sub_info->wait;

	/* CLONE_VFORK: wait until the usermode helper has execve'd
	 * successfully We need the data structures to stay around
	 * until that is done.  */
	if (wait)
		pid = kernel_thread(wait_for_helper, sub_info,
				    CLONE_FS | CLONE_FILES | SIGCHLD);
	else
		pid = kernel_thread(____call_usermodehelper, sub_info,
				    CLONE_VFORK | SIGCHLD);

	if (pid < 0) {
		sub_info->retval = pid;
		complete(sub_info->complete);
	} else if (!wait)
		complete(sub_info->complete);
}

/**
 * call_usermodehelper_keys - start a usermode application
 * @path: pathname for the application
 * @argv: null-terminated argument list
 * @envp: null-terminated environment list
 * @session_keyring: session keyring for process (NULL for an empty keyring)
 * @wait: wait for the application to finish and return status.
 *
 * Runs a user-space application.  The application is started
 * asynchronously if wait is not set, and runs as a child of keventd.
 * (ie. it runs with full root capabilities).
 *
 * Must be called from process context.  Returns a negative error code
 * if program was not execed successfully, or 0.
 */
int call_usermodehelper_keys(char *path, char **argv, char **envp,
			     struct key *session_keyring, int wait)
{
	DECLARE_COMPLETION_ONSTACK(done);
	struct subprocess_info sub_info = {
		.complete	= &done,
		.path		= path,
		.argv		= argv,
		.envp		= envp,
		.ring		= session_keyring,
		.wait		= wait,
		.retval		= 0,
	};
	DECLARE_WORK(work, __call_usermodehelper, &sub_info);

	if (!khelper_wq)
		return -EBUSY;

	if (path[0] == '\0')
		return 0;

	queue_work(khelper_wq, &work);
	wait_for_completion(&done);
	return sub_info.retval;
}
EXPORT_SYMBOL(call_usermodehelper_keys);

void __init usermodehelper_init(void)
{
	khelper_wq = create_singlethread_workqueue("khelper");
	BUG_ON(!khelper_wq);
}
Commit	Line	Data
1da177e4 LT	1	/*
	2	kmod, the new module loader (replaces kerneld)
	3	Kirk Petersen
	4
	5	Reorganized not to be a daemon by Adam Richter, with guidance
	6	from Greg Zornetzer.
	7
	8	Modified to avoid chroot and file sharing problems.
	9	Mikael Pettersson
	10
	11	Limit the concurrent number of kmod modprobes to catch loops from
	12	"modprobe needs a service that is in a module".
	13	Keith Owens <[email protected]> December 1999
	14
	15	Unblock all signals when we exec a usermode process.
	16	Shuu Yamaguchi <[email protected]> December 2000
	17
	18	call_usermodehelper wait flag, and remove exec_usermodehelper.
	19	Rusty Russell <[email protected]> Jan 2003
	20	*/
	21	#define __KERNEL_SYSCALLS__
	22
1da177e4 LT	23	#include <linux/module.h>
	24	#include <linux/sched.h>
	25	#include <linux/syscalls.h>
	26	#include <linux/unistd.h>
	27	#include <linux/kmod.h>
	28	#include <linux/smp_lock.h>
	29	#include <linux/slab.h>
	30	#include <linux/namespace.h>
	31	#include <linux/completion.h>
	32	#include <linux/file.h>
	33	#include <linux/workqueue.h>
	34	#include <linux/security.h>
	35	#include <linux/mount.h>
	36	#include <linux/kernel.h>
	37	#include <linux/init.h>
	38	#include <asm/uaccess.h>
	39
	40	extern int max_threads;
	41
	42	static struct workqueue_struct *khelper_wq;
	43
	44	#ifdef CONFIG_KMOD
	45
	46	/*
	47	modprobe_path is set via /proc/sys.
	48	*/
	49	char modprobe_path[KMOD_PATH_LEN] = "/sbin/modprobe";
	50
	51	/**
	52	* request_module - try to load a kernel module
	53	* @fmt: printf style format string for the name of the module
	54	* @varargs: arguements as specified in the format string
	55	*
	56	* Load a module using the user mode module loader. The function returns
	57	* zero on success or a negative errno code on failure. Note that a
	58	* successful module load does not mean the module did not then unload
	59	* and exit on an error of its own. Callers must check that the service
	60	* they requested is now available not blindly invoke it.
	61	*
	62	* If module auto-loading support is disabled then this function
	63	* becomes a no-operation.
	64	*/
	65	int request_module(const char *fmt, ...)
	66	{
	67	va_list args;
	68	char module_name[MODULE_NAME_LEN];
	69	unsigned int max_modprobes;
	70	int ret;
	71	char *argv[] = { modprobe_path, "-q", "--", module_name, NULL };
	72	static char *envp[] = { "HOME=/",
	73	"TERM=linux",
	74	"PATH=/sbin:/usr/sbin:/bin:/usr/bin",
	75	NULL };
	76	static atomic_t kmod_concurrent = ATOMIC_INIT(0);
	77	#define MAX_KMOD_CONCURRENT 50 /* Completely arbitrary value - KAO */
	78	static int kmod_loop_msg;
	79
	80	va_start(args, fmt);
	81	ret = vsnprintf(module_name, MODULE_NAME_LEN, fmt, args);
	82	va_end(args);
	83	if (ret >= MODULE_NAME_LEN)
	84	return -ENAMETOOLONG;
	85
	86	/* If modprobe needs a service that is in a module, we get a recursive
87	* loop. Limit the number of running kmod threads to max_threads/2 or
88	* MAX_KMOD_CONCURRENT, whichever is the smaller. A cleaner method
89	* would be to run the parents of this process, counting how many times
90	* kmod was invoked. That would mean accessing the internals of the
91	* process tables to get the command line, proc_pid_cmdline is static
92	* and it is not worth changing the proc code just to handle this case.
93	* KAO.
94	*
95	* "trace the ppid" is simple, but will fail if someone's
96	* parent exits. I think this is as good as it gets. --RR
97	*/
98	max_modprobes = min(max_threads/2, MAX_KMOD_CONCURRENT);
99	atomic_inc(&kmod_concurrent);
100	if (atomic_read(&kmod_concurrent) > max_modprobes) {
101	/* We may be blaming an innocent here, but unlikely */
102	if (kmod_loop_msg++ < 5)
103	printk(KERN_ERR
104	"request_module: runaway loop modprobe %s\n",
105	module_name);
106	atomic_dec(&kmod_concurrent);
107	return -ENOMEM;
108	}
109
110	ret = call_usermodehelper(modprobe_path, argv, envp, 1);
111	atomic_dec(&kmod_concurrent);
112	return ret;
113	}
114	EXPORT_SYMBOL(request_module);
115	#endif /* CONFIG_KMOD */
116
117	struct subprocess_info {
118	struct completion *complete;
119	char *path;
120	char **argv;
121	char **envp;
7888e7ff	122	struct key *ring;
1da177e4 LT	123	int wait;
	124	int retval;
	125	};
	126
	127	/*
	128	* This is the task which runs the usermode application
	129	*/
	130	static int ____call_usermodehelper(void *data)
	131	{
	132	struct subprocess_info *sub_info = data;
20e1129a	133	struct key new_session, old_session;
1da177e4 LT	134	int retval;
1da177e4 LT	135
7888e7ff	136	/* Unblock all signals and set the session keyring. */
20e1129a	137	new_session = key_get(sub_info->ring);
1da177e4 LT	138	flush_signals(current);
1da177e4 LT	139	spin_lock_irq(&current->sighand->siglock);
20e1129a	140	old_session = __install_session_keyring(current, new_session);
1da177e4 LT	141	flush_signal_handlers(current, 1);
	142	sigemptyset(&current->blocked);
	143	recalc_sigpending();
	144	spin_unlock_irq(&current->sighand->siglock);
	145
7888e7ff DH	146	key_put(old_session);
7888e7ff DH	147
1da177e4 LT	148	/* We can run anywhere, unlike our parent keventd(). */
	149	set_cpus_allowed(current, CPU_MASK_ALL);
	150
	151	retval = -EPERM;
	152	if (current->fs->root)
	153	retval = execve(sub_info->path, sub_info->argv,sub_info->envp);
	154
	155	/* Exec failed? */
	156	sub_info->retval = retval;
	157	do_exit(0);
	158	}
	159
	160	/* Keventd can't block, but this (a child) can. */
	161	static int wait_for_helper(void *data)
	162	{
	163	struct subprocess_info *sub_info = data;
	164	pid_t pid;
	165	struct k_sigaction sa;
	166
	167	/* Install a handler: if SIGCLD isn't handled sys_wait4 won't
	168	* populate the status, but will return -ECHILD. */
	169	sa.sa.sa_handler = SIG_IGN;
	170	sa.sa.sa_flags = 0;
	171	siginitset(&sa.sa.sa_mask, sigmask(SIGCHLD));
8292d633	172	do_sigaction(SIGCHLD, &sa, NULL);
1da177e4 LT	173	allow_signal(SIGCHLD);
	174
	175	pid = kernel_thread(____call_usermodehelper, sub_info, SIGCHLD);
	176	if (pid < 0) {
	177	sub_info->retval = pid;
	178	} else {
	179	/*
	180	* Normally it is bogus to call wait4() from in-kernel because
	181	* wait4() wants to write the exit code to a userspace address.
	182	* But wait_for_helper() always runs as keventd, and put_user()
	183	* to a kernel address works OK for kernel threads, due to their
	184	* having an mm_segment_t which spans the entire address space.
	185	*
	186	* Thus the __user pointer cast is valid here.
	187	*/
	188	sys_wait4(pid, (int __user *) &sub_info->retval, 0, NULL);
	189	}
	190
	191	complete(sub_info->complete);
	192	return 0;
	193	}
	194
	195	/* This is run by khelper thread */
	196	static void __call_usermodehelper(void *data)
	197	{
	198	struct subprocess_info *sub_info = data;
	199	pid_t pid;
e4b69aa2	200	int wait = sub_info->wait;
1da177e4 LT	201
	202	/* CLONE_VFORK: wait until the usermode helper has execve'd
	203	* successfully We need the data structures to stay around
	204	* until that is done. */
e4b69aa2	205	if (wait)
1da177e4 LT	206	pid = kernel_thread(wait_for_helper, sub_info,
	207	CLONE_FS \| CLONE_FILES \| SIGCHLD);
	208	else
	209	pid = kernel_thread(____call_usermodehelper, sub_info,
	210	CLONE_VFORK \| SIGCHLD);
	211
	212	if (pid < 0) {
	213	sub_info->retval = pid;
	214	complete(sub_info->complete);
e4b69aa2	215	} else if (!wait)
1da177e4 LT	216	complete(sub_info->complete);
	217	}
	218
	219	/**
7888e7ff	220	* call_usermodehelper_keys - start a usermode application
1da177e4 LT	221	* @path: pathname for the application
	222	* @argv: null-terminated argument list
	223	* @envp: null-terminated environment list
7888e7ff	224	* @session_keyring: session keyring for process (NULL for an empty keyring)
1da177e4 LT	225	* @wait: wait for the application to finish and return status.
	226	*
	227	* Runs a user-space application. The application is started
	228	* asynchronously if wait is not set, and runs as a child of keventd.
	229	* (ie. it runs with full root capabilities).
	230	*
	231	* Must be called from process context. Returns a negative error code
	232	* if program was not execed successfully, or 0.
	233	*/
7888e7ff DH	234	int call_usermodehelper_keys(char path, char argv, char *envp,
7888e7ff DH	235	struct key *session_keyring, int wait)
1da177e4	236	{
60be6b9a	237	DECLARE_COMPLETION_ONSTACK(done);
1da177e4 LT	238	struct subprocess_info sub_info = {
	239	.complete = &done,
	240	.path = path,
	241	.argv = argv,
	242	.envp = envp,
7888e7ff	243	.ring = session_keyring,
1da177e4 LT	244	.wait = wait,
	245	.retval = 0,
	246	};
	247	DECLARE_WORK(work, __call_usermodehelper, &sub_info);
	248
	249	if (!khelper_wq)
	250	return -EBUSY;
	251
	252	if (path[0] == '\0')
	253	return 0;
	254
	255	queue_work(khelper_wq, &work);
	256	wait_for_completion(&done);
	257	return sub_info.retval;
	258	}
7888e7ff	259	EXPORT_SYMBOL(call_usermodehelper_keys);
1da177e4 LT	260
	261	void __init usermodehelper_init(void)
	262	{
	263	khelper_wq = create_singlethread_workqueue("khelper");
	264	BUG_ON(!khelper_wq);
	265	}