LXR linux/kernel/kmod.c

   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);
 179