1/*
  2 * kmod - the kernel module loader
  3 */
  4#include <linux/module.h>
  5#include <linux/sched.h>
  6#include <linux/sched/task.h>
  7#include <linux/binfmts.h>
  8#include <linux/syscalls.h>
  9#include <linux/unistd.h>
 10#include <linux/kmod.h>
 11#include <linux/slab.h>
 12#include <linux/completion.h>
 13#include <linux/cred.h>
 14#include <linux/file.h>
 15#include <linux/fdtable.h>
 16#include <linux/workqueue.h>
 17#include <linux/security.h>
 18#include <linux/mount.h>
 19#include <linux/kernel.h>
 20#include <linux/init.h>
 21#include <linux/resource.h>
 22#include <linux/notifier.h>
 23#include <linux/suspend.h>
 24#include <linux/rwsem.h>
 25#include <linux/ptrace.h>
 26#include <linux/async.h>
 27#include <linux/uaccess.h>
 28
 29#include <trace/events/module.h>
 30
 31/*
 32 * Assuming:
 33 *
 34 * threads = div64_u64((u64) totalram_pages * (u64) PAGE_SIZE,
 35 *		       (u64) THREAD_SIZE * 8UL);
 36 *
 37 * If you need less than 50 threads would mean we're dealing with systems
 38 * smaller than 3200 pages. This assumes you are capable of having ~13M memory,
 39 * and this would only be an upper limit, after which the OOM killer would take
 40 * effect. Systems like these are very unlikely if modules are enabled.
 41 */
 42#define MAX_KMOD_CONCURRENT 50
 43static atomic_t kmod_concurrent_max = ATOMIC_INIT(MAX_KMOD_CONCURRENT);
 44static DECLARE_WAIT_QUEUE_HEAD(kmod_wq);
 45
 46/*
 47 * This is a restriction on having *all* MAX_KMOD_CONCURRENT threads
 48 * running at the same time without returning. When this happens we
 49 * believe you've somehow ended up with a recursive module dependency
 50 * creating a loop.
 51 *
 52 * We have no option but to fail.
 53 *
 54 * Userspace should proactively try to detect and prevent these.
 55 */
 56#define MAX_KMOD_ALL_BUSY_TIMEOUT 5
 57
 58/*
 59	modprobe_path is set via /proc/sys.
 60*/
 61char modprobe_path[KMOD_PATH_LEN] = CONFIG_MODPROBE_PATH;
 62
 63static void free_modprobe_argv(struct subprocess_info *info)
 64{
 65	kfree(info->argv[3]); /* check call_modprobe() */
 66	kfree(info->argv);
 67}
 68
 69static int call_modprobe(char *module_name, int wait)
 70{
 71	struct subprocess_info *info;
 72	static char *envp[] = {
 73		"HOME=/",
 74		"TERM=linux",
 75		"PATH=/sbin:/usr/sbin:/bin:/usr/bin",
 76		NULL
 77	};
 78
 79	char **argv = kmalloc(sizeof(char *[5]), GFP_KERNEL);
 80	if (!argv)
 81		goto out;
 82
 83	module_name = kstrdup(module_name, GFP_KERNEL);
 84	if (!module_name)
 85		goto free_argv;
 86
 87	argv[0] = modprobe_path;
 88	argv[1] = "-q";
 89	argv[2] = "--";
 90	argv[3] = module_name;	/* check free_modprobe_argv() */
 91	argv[4] = NULL;
 92
 93	info = call_usermodehelper_setup(modprobe_path, argv, envp, GFP_KERNEL,
 94					 NULL, free_modprobe_argv, NULL);
 95	if (!info)
 96		goto free_module_name;
 97
 98	return call_usermodehelper_exec(info, wait | UMH_KILLABLE);
 99
100free_module_name:
101	kfree(module_name);
102free_argv:
103	kfree(argv);
104out:
105	return -ENOMEM;
106}
107
108/**
109 * __request_module - try to load a kernel module
110 * @wait: wait (or not) for the operation to complete
111 * @fmt: printf style format string for the name of the module
112 * @...: arguments as specified in the format string
113 *
114 * Load a module using the user mode module loader. The function returns
115 * zero on success or a negative errno code or positive exit code from
116 * "modprobe" on failure. Note that a successful module load does not mean
117 * the module did not then unload and exit on an error of its own. Callers
118 * must check that the service they requested is now available not blindly
119 * invoke it.
120 *
121 * If module auto-loading support is disabled then this function
122 * simply returns -ENOENT.
123 */
124int __request_module(bool wait, const char *fmt, ...)
125{
126	va_list args;
127	char module_name[MODULE_NAME_LEN];
128	int ret;
129
130	/*
131	 * We don't allow synchronous module loading from async.  Module
132	 * init may invoke async_synchronize_full() which will end up
133	 * waiting for this task which already is waiting for the module
134	 * loading to complete, leading to a deadlock.
135	 */
136	WARN_ON_ONCE(wait && current_is_async());
137
138	if (!modprobe_path[0])
139		return -ENOENT;
140
141	va_start(args, fmt);
142	ret = vsnprintf(module_name, MODULE_NAME_LEN, fmt, args);
143	va_end(args);
144	if (ret >= MODULE_NAME_LEN)
145		return -ENAMETOOLONG;
146
147	ret = security_kernel_module_request(module_name);
148	if (ret)
149		return ret;
150
151	if (atomic_dec_if_positive(&kmod_concurrent_max) < 0) {
152		pr_warn_ratelimited("request_module: kmod_concurrent_max (%u) close to 0 (max_modprobes: %u), for module %s, throttling...",
153				    atomic_read(&kmod_concurrent_max),
154				    MAX_KMOD_CONCURRENT, module_name);
155		ret = wait_event_killable_timeout(kmod_wq,
156						  atomic_dec_if_positive(&kmod_concurrent_max) >= 0,
157						  MAX_KMOD_ALL_BUSY_TIMEOUT * HZ);
158		if (!ret) {
159			pr_warn_ratelimited("request_module: modprobe %s cannot be processed, kmod busy with %d threads for more than %d seconds now",
160					    module_name, MAX_KMOD_CONCURRENT, MAX_KMOD_ALL_BUSY_TIMEOUT);
161			return -ETIME;
162		} else if (ret == -ERESTARTSYS) {
163			pr_warn_ratelimited("request_module: sigkill sent for modprobe %s, giving up", module_name);
164			return ret;
165		}
166	}
167
168	trace_module_request(module_name, wait, _RET_IP_);
169
170	ret = call_modprobe(module_name, wait ? UMH_WAIT_PROC : UMH_WAIT_EXEC);
171
172	atomic_inc(&kmod_concurrent_max);
173	wake_up(&kmod_wq);
174
175	return ret;
176}
177EXPORT_SYMBOL(__request_module);