1 files changed, 256 insertions, 0 deletions
diff --git a/kernel/kmod.c b/kernel/kmod.c
new file mode 100644
index 00000000000..eed53d4f523
--- /dev/null
+++ b/kernel/kmod.c
@@ -0,0 +1,256 @@
+/*
+	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
+*/
+#define __KERNEL_SYSCALLS__
+
+#include <linux/config.h>
+#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;
+	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;
+	int retval;
+
+	/* Unblock all signals. */
+	flush_signals(current);
+	spin_lock_irq(&current->sighand->siglock);
+	flush_signal_handlers(current, 1);
+	sigemptyset(&current->blocked);
+	recalc_sigpending();
+	spin_unlock_irq(&current->sighand->siglock);
+
+	/* 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, (struct k_sigaction *)0);
+	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;
+
+	/* CLONE_VFORK: wait until the usermode helper has execve'd
+	 * successfully We need the data structures to stay around
+	 * until that is done.  */
+	if (sub_info->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 (!sub_info->wait)
+		complete(sub_info->complete);
+}
+
+/**
+ * call_usermodehelper - start a usermode application
+ * @path: pathname for the application
+ * @argv: null-terminated argument list
+ * @envp: null-terminated environment list
+ * @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(char *path, char **argv, char **envp, int wait)
+{
+	DECLARE_COMPLETION(done);
+	struct subprocess_info sub_info = {
+		.complete	= &done,
+		.path		= path,
+		.argv		= argv,
+		.envp		= envp,
+		.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);
+
+void __init usermodehelper_init(void)
+{
+	khelper_wq = create_singlethread_workqueue("khelper");
+	BUG_ON(!khelper_wq);
+}