[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
*/
#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/mnt_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 <linux/resource.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 work_struct work;
	struct completion *complete;
	char *path;
	char **argv;
	char **envp;
	struct key *ring;
	int wait;
	int retval;
	struct file *stdin;
};

/*
 * 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);

	/* Install input pipe when needed */
	if (sub_info->stdin) {
		struct files_struct *f = current->files;
		struct fdtable *fdt;
		/* no races because files should be private here */
		sys_close(0);
		fd_install(0, sub_info->stdin);
		spin_lock(&f->file_lock);
		fdt = files_fdtable(f);
		FD_SET(0, fdt->open_fds);
		FD_CLR(0, fdt->close_on_exec);
		spin_unlock(&f->file_lock);

		/* and disallow core files too */
		current->signal->rlim[RLIMIT_CORE] = (struct rlimit){0, 0};
	}

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

	retval = -EPERM;
	if (current->fs->root)
		retval = kernel_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 {
		int ret;

		/*
		 * 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 *)&ret, 0, NULL);

		/*
		 * If ret is 0, either ____call_usermodehelper failed and the
		 * real error code is already in sub_info->retval or
		 * sub_info->retval is 0 anyway, so don't mess with it then.
		 */
		if (ret)
			sub_info->retval = ret;
	}

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

/* This is run by khelper thread  */
static void __call_usermodehelper(struct work_struct *work)
{
	struct subprocess_info *sub_info =
		container_of(work, struct subprocess_info, work);
	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 = {
		.work		= __WORK_INITIALIZER(sub_info.work,
						     __call_usermodehelper),
		.complete	= &done,
		.path		= path,
		.argv		= argv,
		.envp		= envp,
		.ring		= session_keyring,
		.wait		= wait,
		.retval		= 0,
	};

	if (!khelper_wq)
		return -EBUSY;

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

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

int call_usermodehelper_pipe(char *path, char **argv, char **envp,
			     struct file **filp)
{
	DECLARE_COMPLETION(done);
	struct subprocess_info sub_info = {
		.work		= __WORK_INITIALIZER(sub_info.work,
						     __call_usermodehelper),
		.complete	= &done,
		.path		= path,
		.argv		= argv,
		.envp		= envp,
		.retval		= 0,
	};
	struct file *f;

	if (!khelper_wq)
		return -EBUSY;

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

	f = create_write_pipe();
	if (IS_ERR(f))
		return PTR_ERR(f);
	*filp = f;

	f = create_read_pipe(f);
	if (IS_ERR(f)) {
		free_write_pipe(*filp);
		return PTR_ERR(f);
	}
	sub_info.stdin = f;

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

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	*/
1da177e4 LT	21	#include <linux/module.h>
	22	#include <linux/sched.h>
	23	#include <linux/syscalls.h>
	24	#include <linux/unistd.h>
	25	#include <linux/kmod.h>
	26	#include <linux/smp_lock.h>
	27	#include <linux/slab.h>
6b3286ed	28	#include <linux/mnt_namespace.h>
1da177e4 LT	29	#include <linux/completion.h>
	30	#include <linux/file.h>
	31	#include <linux/workqueue.h>
	32	#include <linux/security.h>
	33	#include <linux/mount.h>
	34	#include <linux/kernel.h>
	35	#include <linux/init.h>
d025c9db	36	#include <linux/resource.h>
1da177e4 LT	37	#include <asm/uaccess.h>
	38
	39	extern int max_threads;
	40
	41	static struct workqueue_struct *khelper_wq;
	42
	43	#ifdef CONFIG_KMOD
	44
	45	/*
	46	modprobe_path is set via /proc/sys.
	47	*/
	48	char modprobe_path[KMOD_PATH_LEN] = "/sbin/modprobe";
	49
	50	/**
	51	* request_module - try to load a kernel module
	52	* @fmt: printf style format string for the name of the module
	53	* @varargs: arguements as specified in the format string
	54	*
	55	* Load a module using the user mode module loader. The function returns
	56	* zero on success or a negative errno code on failure. Note that a
	57	* successful module load does not mean the module did not then unload
	58	* and exit on an error of its own. Callers must check that the service
	59	* they requested is now available not blindly invoke it.
	60	*
	61	* If module auto-loading support is disabled then this function
	62	* becomes a no-operation.
	63	*/
	64	int request_module(const char *fmt, ...)
	65	{
	66	va_list args;
	67	char module_name[MODULE_NAME_LEN];
	68	unsigned int max_modprobes;
	69	int ret;
	70	char *argv[] = { modprobe_path, "-q", "--", module_name, NULL };
	71	static char *envp[] = { "HOME=/",
	72	"TERM=linux",
	73	"PATH=/sbin:/usr/sbin:/bin:/usr/bin",
	74	NULL };
	75	static atomic_t kmod_concurrent = ATOMIC_INIT(0);
	76	#define MAX_KMOD_CONCURRENT 50 /* Completely arbitrary value - KAO */
	77	static int kmod_loop_msg;
	78
	79	va_start(args, fmt);
	80	ret = vsnprintf(module_name, MODULE_NAME_LEN, fmt, args);
	81	va_end(args);
	82	if (ret >= MODULE_NAME_LEN)
	83	return -ENAMETOOLONG;
	84
	85	/* If modprobe needs a service that is in a module, we get a recursive
	86	* loop. Limit the number of running kmod threads to max_threads/2 or
	87	* MAX_KMOD_CONCURRENT, whichever is the smaller. A cleaner method
	88	* would be to run the parents of this process, counting how many times
	89	* kmod was invoked. That would mean accessing the internals of the
	90	* process tables to get the command line, proc_pid_cmdline is static
	91	* and it is not worth changing the proc code just to handle this case.
	92	* KAO.
	93	*
	94	* "trace the ppid" is simple, but will fail if someone's
	95	* parent exits. I think this is as good as it gets. --RR
	96	*/
	97	max_modprobes = min(max_threads/2, MAX_KMOD_CONCURRENT);
	98	atomic_inc(&kmod_concurrent);
	99	if (atomic_read(&kmod_concurrent) > max_modprobes) {
	100	/* We may be blaming an innocent here, but unlikely */
101	if (kmod_loop_msg++ < 5)
102	printk(KERN_ERR
103	"request_module: runaway loop modprobe %s\n",
104	module_name);
105	atomic_dec(&kmod_concurrent);
106	return -ENOMEM;
107	}
108
109	ret = call_usermodehelper(modprobe_path, argv, envp, 1);
110	atomic_dec(&kmod_concurrent);
111	return ret;
112	}
113	EXPORT_SYMBOL(request_module);
114	#endif /* CONFIG_KMOD */
115
116	struct subprocess_info {
65f27f38	117	struct work_struct work;
1da177e4 LT	118	struct completion *complete;
	119	char *path;
	120	char **argv;
	121	char **envp;
7888e7ff	122	struct key *ring;
1da177e4 LT	123	int wait;
1da177e4 LT	124	int retval;
e239ca54	125	struct file *stdin;
1da177e4 LT	126	};
	127
	128	/*
	129	* This is the task which runs the usermode application
	130	*/
	131	static int ____call_usermodehelper(void *data)
	132	{
	133	struct subprocess_info *sub_info = data;
20e1129a	134	struct key new_session, old_session;
1da177e4 LT	135	int retval;
1da177e4 LT	136
7888e7ff	137	/* Unblock all signals and set the session keyring. */
20e1129a	138	new_session = key_get(sub_info->ring);
1da177e4 LT	139	flush_signals(current);
1da177e4 LT	140	spin_lock_irq(&current->sighand->siglock);
20e1129a	141	old_session = __install_session_keyring(current, new_session);
1da177e4 LT	142	flush_signal_handlers(current, 1);
	143	sigemptyset(&current->blocked);
	144	recalc_sigpending();
	145	spin_unlock_irq(&current->sighand->siglock);
	146
7888e7ff DH	147	key_put(old_session);
7888e7ff DH	148
e239ca54 AK	149	/* Install input pipe when needed */
	150	if (sub_info->stdin) {
	151	struct files_struct *f = current->files;
	152	struct fdtable *fdt;
	153	/* no races because files should be private here */
	154	sys_close(0);
	155	fd_install(0, sub_info->stdin);
	156	spin_lock(&f->file_lock);
	157	fdt = files_fdtable(f);
	158	FD_SET(0, fdt->open_fds);
	159	FD_CLR(0, fdt->close_on_exec);
	160	spin_unlock(&f->file_lock);
d025c9db AK	161
	162	/* and disallow core files too */
	163	current->signal->rlim[RLIMIT_CORE] = (struct rlimit){0, 0};
e239ca54 AK	164	}
e239ca54 AK	165
1da177e4 LT	166	/* We can run anywhere, unlike our parent keventd(). */
	167	set_cpus_allowed(current, CPU_MASK_ALL);
	168
	169	retval = -EPERM;
	170	if (current->fs->root)
67608567 AB	171	retval = kernel_execve(sub_info->path,
67608567 AB	172	sub_info->argv, sub_info->envp);
1da177e4 LT	173
	174	/* Exec failed? */
	175	sub_info->retval = retval;
	176	do_exit(0);
	177	}
	178
	179	/* Keventd can't block, but this (a child) can. */
	180	static int wait_for_helper(void *data)
	181	{
	182	struct subprocess_info *sub_info = data;
	183	pid_t pid;
	184	struct k_sigaction sa;
	185
	186	/* Install a handler: if SIGCLD isn't handled sys_wait4 won't
	187	* populate the status, but will return -ECHILD. */
	188	sa.sa.sa_handler = SIG_IGN;
	189	sa.sa.sa_flags = 0;
	190	siginitset(&sa.sa.sa_mask, sigmask(SIGCHLD));
8292d633	191	do_sigaction(SIGCHLD, &sa, NULL);
1da177e4 LT	192	allow_signal(SIGCHLD);
	193
	194	pid = kernel_thread(____call_usermodehelper, sub_info, SIGCHLD);
	195	if (pid < 0) {
	196	sub_info->retval = pid;
	197	} else {
111dbe0c BS	198	int ret;
111dbe0c BS	199
1da177e4 LT	200	/*
	201	* Normally it is bogus to call wait4() from in-kernel because
	202	* wait4() wants to write the exit code to a userspace address.
	203	* But wait_for_helper() always runs as keventd, and put_user()
	204	* to a kernel address works OK for kernel threads, due to their
	205	* having an mm_segment_t which spans the entire address space.
	206	*
	207	* Thus the __user pointer cast is valid here.
	208	*/
111dbe0c BS	209	sys_wait4(pid, (int __user *)&ret, 0, NULL);
	210
	211	/*
	212	* If ret is 0, either ____call_usermodehelper failed and the
	213	* real error code is already in sub_info->retval or
	214	* sub_info->retval is 0 anyway, so don't mess with it then.
	215	*/
	216	if (ret)
	217	sub_info->retval = ret;
1da177e4 LT	218	}
	219
	220	complete(sub_info->complete);
	221	return 0;
	222	}
	223
	224	/* This is run by khelper thread */
65f27f38	225	static void __call_usermodehelper(struct work_struct *work)
1da177e4	226	{
65f27f38 DH	227	struct subprocess_info *sub_info =
65f27f38 DH	228	container_of(work, struct subprocess_info, work);
1da177e4	229	pid_t pid;
e4b69aa2	230	int wait = sub_info->wait;
1da177e4 LT	231
	232	/* CLONE_VFORK: wait until the usermode helper has execve'd
	233	* successfully We need the data structures to stay around
	234	* until that is done. */
e4b69aa2	235	if (wait)
1da177e4 LT	236	pid = kernel_thread(wait_for_helper, sub_info,
	237	CLONE_FS \| CLONE_FILES \| SIGCHLD);
	238	else
	239	pid = kernel_thread(____call_usermodehelper, sub_info,
	240	CLONE_VFORK \| SIGCHLD);
	241
	242	if (pid < 0) {
	243	sub_info->retval = pid;
	244	complete(sub_info->complete);
e4b69aa2	245	} else if (!wait)
1da177e4 LT	246	complete(sub_info->complete);
	247	}
	248
	249	/**
7888e7ff	250	* call_usermodehelper_keys - start a usermode application
1da177e4 LT	251	* @path: pathname for the application
	252	* @argv: null-terminated argument list
	253	* @envp: null-terminated environment list
7888e7ff	254	* @session_keyring: session keyring for process (NULL for an empty keyring)
1da177e4 LT	255	* @wait: wait for the application to finish and return status.
	256	*
	257	* Runs a user-space application. The application is started
	258	* asynchronously if wait is not set, and runs as a child of keventd.
	259	* (ie. it runs with full root capabilities).
	260	*
	261	* Must be called from process context. Returns a negative error code
	262	* if program was not execed successfully, or 0.
	263	*/
7888e7ff DH	264	int call_usermodehelper_keys(char path, char argv, char *envp,
7888e7ff DH	265	struct key *session_keyring, int wait)
1da177e4	266	{
60be6b9a	267	DECLARE_COMPLETION_ONSTACK(done);
1da177e4	268	struct subprocess_info sub_info = {
65f27f38 DH	269	.work = __WORK_INITIALIZER(sub_info.work,
65f27f38 DH	270	__call_usermodehelper),
1da177e4 LT	271	.complete = &done,
	272	.path = path,
	273	.argv = argv,
	274	.envp = envp,
7888e7ff	275	.ring = session_keyring,
1da177e4 LT	276	.wait = wait,
	277	.retval = 0,
	278	};
1da177e4 LT	279
	280	if (!khelper_wq)
	281	return -EBUSY;
	282
	283	if (path[0] == '\0')
	284	return 0;
	285
65f27f38	286	queue_work(khelper_wq, &sub_info.work);
1da177e4 LT	287	wait_for_completion(&done);
	288	return sub_info.retval;
	289	}
7888e7ff	290	EXPORT_SYMBOL(call_usermodehelper_keys);
1da177e4	291
e239ca54 AK	292	int call_usermodehelper_pipe(char path, char argv, char *envp,
	293	struct file **filp)
	294	{
	295	DECLARE_COMPLETION(done);
	296	struct subprocess_info sub_info = {
65f27f38 DH	297	.work = __WORK_INITIALIZER(sub_info.work,
65f27f38 DH	298	__call_usermodehelper),
e239ca54 AK	299	.complete = &done,
	300	.path = path,
	301	.argv = argv,
	302	.envp = envp,
	303	.retval = 0,
	304	};
	305	struct file *f;
e239ca54 AK	306
	307	if (!khelper_wq)
	308	return -EBUSY;
	309
	310	if (path[0] == '\0')
	311	return 0;
	312
	313	f = create_write_pipe();
3cce4856 AM	314	if (IS_ERR(f))
3cce4856 AM	315	return PTR_ERR(f);
e239ca54 AK	316	*filp = f;
	317
	318	f = create_read_pipe(f);
3cce4856	319	if (IS_ERR(f)) {
e239ca54	320	free_write_pipe(*filp);
3cce4856	321	return PTR_ERR(f);
e239ca54 AK	322	}
	323	sub_info.stdin = f;
	324
65f27f38	325	queue_work(khelper_wq, &sub_info.work);
e239ca54 AK	326	wait_for_completion(&done);
	327	return sub_info.retval;
	328	}
	329	EXPORT_SYMBOL(call_usermodehelper_pipe);
	330
1da177e4 LT	331	void __init usermodehelper_init(void)
	332	{
	333	khelper_wq = create_singlethread_workqueue("khelper");
	334	BUG_ON(!khelper_wq);
	335	}