[linux-2.6-block.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 <kaos@ocs.com.au> December 1999

	Unblock all signals when we exec a usermode process.
	Shuu Yamaguchi <shuu@wondernetworkresources.com> December 2000

	call_usermodehelper wait flag, and remove exec_usermodehelper.
	Rusty Russell <rusty@rustcorp.com.au>  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/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 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(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);

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

	if (!khelper_wq)
		return -EBUSY;

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

	f = create_write_pipe();
	if (!f)
		return -ENOMEM;
	*filp = f;

	f = create_read_pipe(f);
	if (!f) {
		free_write_pipe(*filp);
		return -ENOMEM;
	}
	sub_info.stdin = f;

	queue_work(khelper_wq, &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 <kaos@ocs.com.au> December 1999
	14
	15	Unblock all signals when we exec a usermode process.
	16	Shuu Yamaguchi <shuu@wondernetworkresources.com> December 2000
	17
	18	call_usermodehelper wait flag, and remove exec_usermodehelper.
	19	Rusty Russell <rusty@rustcorp.com.au> 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>
	28	#include <linux/namespace.h>
	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 {
117	struct completion *complete;
118	char *path;
119	char **argv;
120	char **envp;
7888e7ff	121	struct key *ring;
1da177e4 LT	122	int wait;
1da177e4 LT	123	int retval;
e239ca54	124	struct file *stdin;
1da177e4 LT	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
e239ca54 AK	148	/* Install input pipe when needed */
	149	if (sub_info->stdin) {
	150	struct files_struct *f = current->files;
	151	struct fdtable *fdt;
	152	/* no races because files should be private here */
	153	sys_close(0);
	154	fd_install(0, sub_info->stdin);
	155	spin_lock(&f->file_lock);
	156	fdt = files_fdtable(f);
	157	FD_SET(0, fdt->open_fds);
	158	FD_CLR(0, fdt->close_on_exec);
	159	spin_unlock(&f->file_lock);
d025c9db AK	160
	161	/* and disallow core files too */
	162	current->signal->rlim[RLIMIT_CORE] = (struct rlimit){0, 0};
e239ca54 AK	163	}
e239ca54 AK	164
1da177e4 LT	165	/* We can run anywhere, unlike our parent keventd(). */
	166	set_cpus_allowed(current, CPU_MASK_ALL);
	167
	168	retval = -EPERM;
	169	if (current->fs->root)
67608567 AB	170	retval = kernel_execve(sub_info->path,
67608567 AB	171	sub_info->argv, sub_info->envp);
1da177e4 LT	172
	173	/* Exec failed? */
	174	sub_info->retval = retval;
	175	do_exit(0);
	176	}
	177
	178	/* Keventd can't block, but this (a child) can. */
	179	static int wait_for_helper(void *data)
	180	{
	181	struct subprocess_info *sub_info = data;
	182	pid_t pid;
	183	struct k_sigaction sa;
	184
	185	/* Install a handler: if SIGCLD isn't handled sys_wait4 won't
	186	* populate the status, but will return -ECHILD. */
	187	sa.sa.sa_handler = SIG_IGN;
	188	sa.sa.sa_flags = 0;
	189	siginitset(&sa.sa.sa_mask, sigmask(SIGCHLD));
8292d633	190	do_sigaction(SIGCHLD, &sa, NULL);
1da177e4 LT	191	allow_signal(SIGCHLD);
	192
	193	pid = kernel_thread(____call_usermodehelper, sub_info, SIGCHLD);
	194	if (pid < 0) {
	195	sub_info->retval = pid;
	196	} else {
111dbe0c BS	197	int ret;
111dbe0c BS	198
1da177e4 LT	199	/*
	200	* Normally it is bogus to call wait4() from in-kernel because
	201	* wait4() wants to write the exit code to a userspace address.
	202	* But wait_for_helper() always runs as keventd, and put_user()
	203	* to a kernel address works OK for kernel threads, due to their
	204	* having an mm_segment_t which spans the entire address space.
	205	*
	206	* Thus the __user pointer cast is valid here.
	207	*/
111dbe0c BS	208	sys_wait4(pid, (int __user *)&ret, 0, NULL);
	209
	210	/*
	211	* If ret is 0, either ____call_usermodehelper failed and the
	212	* real error code is already in sub_info->retval or
	213	* sub_info->retval is 0 anyway, so don't mess with it then.
	214	*/
	215	if (ret)
	216	sub_info->retval = ret;
1da177e4 LT	217	}
	218
	219	complete(sub_info->complete);
	220	return 0;
	221	}
	222
	223	/* This is run by khelper thread */
	224	static void __call_usermodehelper(void *data)
	225	{
	226	struct subprocess_info *sub_info = data;
	227	pid_t pid;
e4b69aa2	228	int wait = sub_info->wait;
1da177e4 LT	229
	230	/* CLONE_VFORK: wait until the usermode helper has execve'd
	231	* successfully We need the data structures to stay around
	232	* until that is done. */
e4b69aa2	233	if (wait)
1da177e4 LT	234	pid = kernel_thread(wait_for_helper, sub_info,
	235	CLONE_FS \| CLONE_FILES \| SIGCHLD);
	236	else
	237	pid = kernel_thread(____call_usermodehelper, sub_info,
	238	CLONE_VFORK \| SIGCHLD);
	239
	240	if (pid < 0) {
	241	sub_info->retval = pid;
	242	complete(sub_info->complete);
e4b69aa2	243	} else if (!wait)
1da177e4 LT	244	complete(sub_info->complete);
	245	}
	246
	247	/**
7888e7ff	248	* call_usermodehelper_keys - start a usermode application
1da177e4 LT	249	* @path: pathname for the application
	250	* @argv: null-terminated argument list
	251	* @envp: null-terminated environment list
7888e7ff	252	* @session_keyring: session keyring for process (NULL for an empty keyring)
1da177e4 LT	253	* @wait: wait for the application to finish and return status.
	254	*
	255	* Runs a user-space application. The application is started
	256	* asynchronously if wait is not set, and runs as a child of keventd.
	257	* (ie. it runs with full root capabilities).
	258	*
	259	* Must be called from process context. Returns a negative error code
	260	* if program was not execed successfully, or 0.
	261	*/
7888e7ff DH	262	int call_usermodehelper_keys(char path, char argv, char *envp,
7888e7ff DH	263	struct key *session_keyring, int wait)
1da177e4	264	{
60be6b9a	265	DECLARE_COMPLETION_ONSTACK(done);
1da177e4 LT	266	struct subprocess_info sub_info = {
	267	.complete = &done,
	268	.path = path,
	269	.argv = argv,
	270	.envp = envp,
7888e7ff	271	.ring = session_keyring,
1da177e4 LT	272	.wait = wait,
	273	.retval = 0,
	274	};
	275	DECLARE_WORK(work, __call_usermodehelper, &sub_info);
	276
	277	if (!khelper_wq)
	278	return -EBUSY;
	279
	280	if (path[0] == '\0')
	281	return 0;
	282
	283	queue_work(khelper_wq, &work);
	284	wait_for_completion(&done);
	285	return sub_info.retval;
	286	}
7888e7ff	287	EXPORT_SYMBOL(call_usermodehelper_keys);
1da177e4	288
e239ca54 AK	289	int call_usermodehelper_pipe(char path, char argv, char *envp,
	290	struct file **filp)
	291	{
	292	DECLARE_COMPLETION(done);
	293	struct subprocess_info sub_info = {
	294	.complete = &done,
	295	.path = path,
	296	.argv = argv,
	297	.envp = envp,
	298	.retval = 0,
	299	};
	300	struct file *f;
	301	DECLARE_WORK(work, __call_usermodehelper, &sub_info);
	302
	303	if (!khelper_wq)
	304	return -EBUSY;
	305
	306	if (path[0] == '\0')
	307	return 0;
	308
	309	f = create_write_pipe();
	310	if (!f)
	311	return -ENOMEM;
	312	*filp = f;
	313
	314	f = create_read_pipe(f);
	315	if (!f) {
	316	free_write_pipe(*filp);
	317	return -ENOMEM;
	318	}
	319	sub_info.stdin = f;
	320
	321	queue_work(khelper_wq, &work);
	322	wait_for_completion(&done);
	323	return sub_info.retval;
	324	}
	325	EXPORT_SYMBOL(call_usermodehelper_pipe);
	326
1da177e4 LT	327	void __init usermodehelper_init(void)
	328	{
	329	khelper_wq = create_singlethread_workqueue("khelper");
	330	BUG_ON(!khelper_wq);
	331	}