Release 4.15 kernel/kmod.c

/*
 * 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 50

static 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);
}

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1
100.00%



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;
}

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Oleg Nesterov
137
80.12%
2
66.67%
Lucas De Marchi
34
19.88%
1
33.33%
Total
171
100.00%
3
100.00%

/**
 * __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;
}
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Luis R. Rodriguez
82
37.10%
3
16.67%
Linus Torvalds
44
19.91%
1
5.56%
Rusty Russell
20
9.05%
2
11.11%
Linus Torvalds (pre-git)
16
7.24%
4
22.22%
Eric Paris
14
6.33%
1
5.56%
Oleg Nesterov
13
5.88%
2
11.11%
Li Zefan
9
4.07%
1
5.56%
Arjan van de Ven
9
4.07%
1
5.56%
Tejun Heo
9
4.07%
1
5.56%
Ingo Molnar
3
1.36%
1
5.56%
Jiri Kosina
2
0.90%
1
5.56%
Total
221
100.00%
18
100.00%


EXPORT_SYMBOL(__request_module);
Overall Contributors
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CommitProp
Oleg Nesterov
179
33.33%
3
6.98%
Luis R. Rodriguez
108
20.11%
4
9.30%
Linus Torvalds
54
10.06%
5
11.63%
Linus Torvalds (pre-git)
38
7.08%
6
13.95%
Lucas De Marchi
34
6.33%
1
2.33%
Rusty Russell
23
4.28%
2
4.65%
Eric Paris
17
3.17%
2
4.65%
Tejun Heo
12
2.23%
1
2.33%
Li Zefan
12
2.23%
1
2.33%
Andrew Morton
11
2.05%
3
6.98%
Arjan van de Ven
10
1.86%
1
2.33%
Ingo Molnar
10
1.86%
4
9.30%
Al Viro
6
1.12%
2
4.65%
Rafael J. Wysocki
6
1.12%
1
2.33%
Greg Kroah-Hartman
3
0.56%
1
2.33%
Christoph Hellwig
3
0.56%
1
2.33%
Srivatsa S. Bhat
3
0.56%
1
2.33%
Andi Kleen
3
0.56%
1
2.33%
Jiri Kosina
2
0.37%
1
2.33%
Matthew Wilcox
2
0.37%
1
2.33%
Neil Brown
1
0.19%
1
2.33%
Total
537
100.00%
43
100.00%
Directory: kernel

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