/* * kmod - the kernel module loader */#include <linux/module.h>#include <linux/sched.h>#include <linux/sched/task.h>#include <linux/binfmts.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 <linux/ptrace.h>#include <linux/async.h>#include <linux/uaccess.h> #include <trace/events/module.h> /* * Assuming: * * threads = div64_u64((u64) totalram_pages * (u64) PAGE_SIZE, *		       (u64) THREAD_SIZE * 8UL); * * If you need less than 50 threads would mean we're dealing with systems * smaller than 3200 pages. This assuems you are capable of having ~13M memory, * and this would only be an be an upper limit, after which the OOM killer * would take effect. Systems like these are very unlikely if modules are * enabled. */#define MAX_KMOD_CONCURRENT 50static atomic_t kmod_concurrent_max = ATOMIC_INIT(MAX_KMOD_CONCURRENT);static DECLARE_WAIT_QUEUE_HEAD(kmod_wq); /* * This is a restriction on having *all* MAX_KMOD_CONCURRENT threads * running at the same time without returning. When this happens we * believe you've somehow ended up with a recursive module dependency * creating a loop. * * We have no option but to fail. * * Userspace should proactively try to detect and prevent these. */#define MAX_KMOD_ALL_BUSY_TIMEOUT 5 /*	modprobe_path is set via /proc/sys.*/char modprobe_path[KMOD_PATH_LEN] = "/sbin/modprobe"; static void free_modprobe_argv(struct subprocess_info *info){	kfree(info->argv[3]); /* check call_modprobe() */	kfree(info->argv);} static int call_modprobe(char *module_name, int wait){	struct subprocess_info *info;	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;	/* check free_modprobe_argv() */	argv[4] = NULL; 	info = call_usermodehelper_setup(modprobe_path, argv, envp, GFP_KERNEL,					 NULL, free_modprobe_argv, NULL);	if (!info)		goto free_module_name; 	return call_usermodehelper_exec(info, wait | UMH_KILLABLE); free_module_name:	kfree(module_name);free_argv:	kfree(argv);out:	return -ENOMEM;} /** * __request_module - try to load a kernel module * @wait: wait (or not) for the operation to complete * @fmt: printf style format string for the name of the module * @...: arguments 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 or positive exit code from * "modprobe" 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(bool wait, const char *fmt, ...){	va_list args;	char module_name[MODULE_NAME_LEN];	int ret; 	/*	 * We don't allow synchronous module loading from async.  Module	 * init may invoke async_synchronize_full() which will end up	 * waiting for this task which already is waiting for the module	 * loading to complete, leading to a deadlock.	 */	WARN_ON_ONCE(wait && current_is_async()); 	if (!modprobe_path[0])		return 0; 	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; 	if (atomic_dec_if_positive(&kmod_concurrent_max) < 0) {		pr_warn_ratelimited("request_module: kmod_concurrent_max (%u) close to 0 (max_modprobes: %u), for module %s, throttling...",				    atomic_read(&kmod_concurrent_max),				    MAX_KMOD_CONCURRENT, module_name);		ret = wait_event_killable_timeout(kmod_wq,						  atomic_dec_if_positive(&kmod_concurrent_max) >= 0,						  MAX_KMOD_ALL_BUSY_TIMEOUT * HZ);		if (!ret) {			pr_warn_ratelimited("request_module: modprobe %s cannot be processed, kmod busy with %d threads for more than %d seconds now",					    module_name, MAX_KMOD_CONCURRENT, MAX_KMOD_ALL_BUSY_TIMEOUT);			return -ETIME;		} else if (ret == -ERESTARTSYS) {			pr_warn_ratelimited("request_module: sigkill sent for modprobe %s, giving up", module_name);			return ret;		}	} 	trace_module_request(module_name, wait, _RET_IP_); 	ret = call_modprobe(module_name, wait ? UMH_WAIT_PROC : UMH_WAIT_EXEC); 	atomic_inc(&kmod_concurrent_max);	wake_up(&kmod_wq); 	return ret;}EXPORT_SYMBOL(__request_module);