1 /* 2 * kmod - the kernel module loader 3 * 4 * Copyright (C) 2023 Luis Chamberlain <mcgrof@kernel.org> 5 */ 6 7 #include <linux/module.h> 8 #include <linux/sched.h> 9 #include <linux/sched/task.h> 10 #include <linux/binfmts.h> 11 #include <linux/syscalls.h> 12 #include <linux/unistd.h> 13 #include <linux/kmod.h> 14 #include <linux/slab.h> 15 #include <linux/completion.h> 16 #include <linux/cred.h> 17 #include <linux/file.h> 18 #include <linux/fdtable.h> 19 #include <linux/workqueue.h> 20 #include <linux/security.h> 21 #include <linux/mount.h> 22 #include <linux/kernel.h> 23 #include <linux/init.h> 24 #include <linux/resource.h> 25 #include <linux/notifier.h> 26 #include <linux/suspend.h> 27 #include <linux/rwsem.h> 28 #include <linux/ptrace.h> 29 #include <linux/async.h> 30 #include <linux/uaccess.h> 31 32 #include <trace/events/module.h> 33 #include "internal.h" 34 35 /* 36 * Assuming: 37 * 38 * threads = div64_u64((u64) totalram_pages * (u64) PAGE_SIZE, 39 * (u64) THREAD_SIZE * 8UL); 40 * 41 * If you need less than 50 threads would mean we're dealing with systems 42 * smaller than 3200 pages. This assumes you are capable of having ~13M memory, 43 * and this would only be an upper limit, after which the OOM killer would take 44 * effect. Systems like these are very unlikely if modules are enabled. 45 */ 46 #define MAX_KMOD_CONCURRENT 50 47 static DEFINE_SEMAPHORE(kmod_concurrent_max, MAX_KMOD_CONCURRENT); 48 49 /* 50 * This is a restriction on having *all* MAX_KMOD_CONCURRENT threads 51 * running at the same time without returning. When this happens we 52 * believe you've somehow ended up with a recursive module dependency 53 * creating a loop. 54 * 55 * We have no option but to fail. 56 * 57 * Userspace should proactively try to detect and prevent these. 58 */ 59 #define MAX_KMOD_ALL_BUSY_TIMEOUT 5 60 61 /* 62 modprobe_path is set via /proc/sys. 63 */ 64 char modprobe_path[KMOD_PATH_LEN] = CONFIG_MODPROBE_PATH; 65 66 static void free_modprobe_argv(struct subprocess_info *info) 67 { 68 kfree(info->argv[3]); /* check call_modprobe() */ 69 kfree(info->argv); 70 } 71 72 static int call_modprobe(char *orig_module_name, int wait) 73 { 74 struct subprocess_info *info; 75 static char *envp[] = { 76 "HOME=/", 77 "TERM=linux", 78 "PATH=/sbin:/usr/sbin:/bin:/usr/bin", 79 NULL 80 }; 81 char *module_name; 82 int ret; 83 84 char **argv = kmalloc(sizeof(char *[5]), GFP_KERNEL); 85 if (!argv) 86 goto out; 87 88 module_name = kstrdup(orig_module_name, GFP_KERNEL); 89 if (!module_name) 90 goto free_argv; 91 92 argv[0] = modprobe_path; 93 argv[1] = "-q"; 94 argv[2] = "--"; 95 argv[3] = module_name; /* check free_modprobe_argv() */ 96 argv[4] = NULL; 97 98 info = call_usermodehelper_setup(modprobe_path, argv, envp, GFP_KERNEL, 99 NULL, free_modprobe_argv, NULL); 100 if (!info) 101 goto free_module_name; 102 103 ret = call_usermodehelper_exec(info, wait | UMH_KILLABLE); 104 kmod_dup_request_announce(orig_module_name, ret); 105 return ret; 106 107 free_module_name: 108 kfree(module_name); 109 free_argv: 110 kfree(argv); 111 out: 112 kmod_dup_request_announce(orig_module_name, -ENOMEM); 113 return -ENOMEM; 114 } 115 116 /** 117 * __request_module - try to load a kernel module 118 * @wait: wait (or not) for the operation to complete 119 * @fmt: printf style format string for the name of the module 120 * @...: arguments as specified in the format string 121 * 122 * Load a module using the user mode module loader. The function returns 123 * zero on success or a negative errno code or positive exit code from 124 * "modprobe" on failure. Note that a successful module load does not mean 125 * the module did not then unload and exit on an error of its own. Callers 126 * must check that the service they requested is now available not blindly 127 * invoke it. 128 * 129 * If module auto-loading support is disabled then this function 130 * simply returns -ENOENT. 131 */ 132 int __request_module(bool wait, const char *fmt, ...) 133 { 134 va_list args; 135 char module_name[MODULE_NAME_LEN]; 136 int ret, dup_ret; 137 138 /* 139 * We don't allow synchronous module loading from async. Module 140 * init may invoke async_synchronize_full() which will end up 141 * waiting for this task which already is waiting for the module 142 * loading to complete, leading to a deadlock. 143 */ 144 WARN_ON_ONCE(wait && current_is_async()); 145 146 if (!modprobe_path[0]) 147 return -ENOENT; 148 149 va_start(args, fmt); 150 ret = vsnprintf(module_name, MODULE_NAME_LEN, fmt, args); 151 va_end(args); 152 if (ret >= MODULE_NAME_LEN) 153 return -ENAMETOOLONG; 154 155 ret = security_kernel_module_request(module_name); 156 if (ret) 157 return ret; 158 159 ret = down_timeout(&kmod_concurrent_max, MAX_KMOD_ALL_BUSY_TIMEOUT * HZ); 160 if (ret) { 161 pr_warn_ratelimited("request_module: modprobe %s cannot be processed, kmod busy with %d threads for more than %d seconds now", 162 module_name, MAX_KMOD_CONCURRENT, MAX_KMOD_ALL_BUSY_TIMEOUT); 163 return ret; 164 } 165 166 trace_module_request(module_name, wait, _RET_IP_); 167 168 if (kmod_dup_request_exists_wait(module_name, wait, &dup_ret)) { 169 ret = dup_ret; 170 goto out; 171 } 172 173 ret = call_modprobe(module_name, wait ? UMH_WAIT_PROC : UMH_WAIT_EXEC); 174 175 out: 176 up(&kmod_concurrent_max); 177 178 return ret; 179 } 180 EXPORT_SYMBOL(__request_module); 181