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 assuems you are capable of having ~13M memory,
 39 * and this would only be an be an upper limit, after which the OOM killer
 40 * would take effect. Systems like these are very unlikely if modules are
 41 * enabled.
 42 */
 43#define MAX_KMOD_CONCURRENT 50
 44static atomic_t kmod_concurrent_max = ATOMIC_INIT(MAX_KMOD_CONCURRENT);
 45static DECLARE_WAIT_QUEUE_HEAD(kmod_wq);
 46
 47/*
 48 * This is a restriction on having *all* MAX_KMOD_CONCURRENT threads
 49 * running at the same time without returning. When this happens we
 50 * believe you've somehow ended up with a recursive module dependency
 51 * creating a loop.
 52 *
 53 * We have no option but to fail.
 54 *
 55 * Userspace should proactively try to detect and prevent these.
 56 */
 57#define MAX_KMOD_ALL_BUSY_TIMEOUT 5
 58
 59/*
 60	modprobe_path is set via /proc/sys.
 61*/
 62char modprobe_path[KMOD_PATH_LEN] = "/sbin/modprobe";
 63
 64static void free_modprobe_argv(struct subprocess_info *info)
 65{
 66	kfree(info->argv[3]); /* check call_modprobe() */
 67	kfree(info->argv);
 68}
 69
 70static int call_modprobe(char *module_name, int wait)
 71{
 72	struct subprocess_info *info;
 73	static char *envp[] = {
 74		"HOME=/",
 75		"TERM=linux",
 76		"PATH=/sbin:/usr/sbin:/bin:/usr/bin",
 77		NULL
 78	};
 79
 80	char **argv = kmalloc(sizeof(char *[5]), GFP_KERNEL);
 81	if (!argv)
 82		goto out;
 83
 84	module_name = kstrdup(module_name, GFP_KERNEL);
 85	if (!module_name)
 86		goto free_argv;
 87
 88	argv[0] = modprobe_path;
 89	argv[1] = "-q";
 90	argv[2] = "--";
 91	argv[3] = module_name;	/* check free_modprobe_argv() */
 92	argv[4] = NULL;
 93
 94	info = call_usermodehelper_setup(modprobe_path, argv, envp, GFP_KERNEL,
 95					 NULL, free_modprobe_argv, NULL);
 96	if (!info)
 97		goto free_module_name;
 98
 99	return call_usermodehelper_exec(info, wait | UMH_KILLABLE);
100
101free_module_name:
102	kfree(module_name);
103free_argv:
104	kfree(argv);
105out:
106	return -ENOMEM;
107}
108
109/**
110 * __request_module - try to load a kernel module
111 * @wait: wait (or not) for the operation to complete
112 * @fmt: printf style format string for the name of the module
113 * @...: arguments as specified in the format string
114 *
115 * Load a module using the user mode module loader. The function returns
116 * zero on success or a negative errno code or positive exit code from
117 * "modprobe" on failure. Note that a successful module load does not mean
118 * the module did not then unload and exit on an error of its own. Callers
119 * must check that the service they requested is now available not blindly
120 * invoke it.
121 *
122 * If module auto-loading support is disabled then this function
123 * becomes a no-operation.
124 */
125int __request_module(bool wait, const char *fmt, ...)
126{
127	va_list args;
128	char module_name[MODULE_NAME_LEN];
129	int ret;
130
131	/*
132	 * We don't allow synchronous module loading from async.  Module
133	 * init may invoke async_synchronize_full() which will end up
134	 * waiting for this task which already is waiting for the module
135	 * loading to complete, leading to a deadlock.
136	 */
137	WARN_ON_ONCE(wait && current_is_async());
138
139	if (!modprobe_path[0])
140		return 0;
141
142	va_start(args, fmt);
143	ret = vsnprintf(module_name, MODULE_NAME_LEN, fmt, args);
144	va_end(args);
145	if (ret >= MODULE_NAME_LEN)
146		return -ENAMETOOLONG;
147
148	ret = security_kernel_module_request(module_name);
149	if (ret)
150		return ret;
151
152	if (atomic_dec_if_positive(&kmod_concurrent_max) < 0) {
153		pr_warn_ratelimited("request_module: kmod_concurrent_max (%u) close to 0 (max_modprobes: %u), for module %s, throttling...",
154				    atomic_read(&kmod_concurrent_max),
155				    MAX_KMOD_CONCURRENT, module_name);
156		ret = wait_event_killable_timeout(kmod_wq,
157						  atomic_dec_if_positive(&kmod_concurrent_max) >= 0,
158						  MAX_KMOD_ALL_BUSY_TIMEOUT * HZ);
159		if (!ret) {
160			pr_warn_ratelimited("request_module: modprobe %s cannot be processed, kmod busy with %d threads for more than %d seconds now",
161					    module_name, MAX_KMOD_CONCURRENT, MAX_KMOD_ALL_BUSY_TIMEOUT);
162			return -ETIME;
163		} else if (ret == -ERESTARTSYS) {
164			pr_warn_ratelimited("request_module: sigkill sent for modprobe %s, giving up", module_name);
165			return ret;
166		}
167	}
168
169	trace_module_request(module_name, wait, _RET_IP_);
170
171	ret = call_modprobe(module_name, wait ? UMH_WAIT_PROC : UMH_WAIT_EXEC);
172
173	atomic_inc(&kmod_concurrent_max);
174	wake_up(&kmod_wq);
175
176	return ret;
177}
178EXPORT_SYMBOL(__request_module);