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
43 static atomic_t kmod_concurrent_max = ATOMIC_INIT(MAX_KMOD_CONCURRENT);
44 static 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 */
61 char modprobe_path[KMOD_PATH_LEN] = "/sbin/modprobe";
62
free_modprobe_argv(struct subprocess_info * info)63 static void free_modprobe_argv(struct subprocess_info *info)
64 {
65 kfree(info->argv[3]); /* check call_modprobe() */
66 kfree(info->argv);
67 }
68
call_modprobe(char * module_name,int wait)69 static 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
100 free_module_name:
101 kfree(module_name);
102 free_argv:
103 kfree(argv);
104 out:
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 */
__request_module(bool wait,const char * fmt,...)124 int __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 }
177 EXPORT_SYMBOL(__request_module);
178