179 lines
5 KiB
C
179 lines
5 KiB
C
/*
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* kmod - the kernel module loader
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*/
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#include <linux/module.h>
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#include <linux/sched.h>
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#include <linux/sched/task.h>
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#include <linux/binfmts.h>
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#include <linux/syscalls.h>
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#include <linux/unistd.h>
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#include <linux/kmod.h>
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#include <linux/slab.h>
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#include <linux/completion.h>
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#include <linux/cred.h>
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#include <linux/file.h>
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#include <linux/fdtable.h>
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#include <linux/workqueue.h>
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#include <linux/security.h>
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#include <linux/mount.h>
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#include <linux/kernel.h>
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#include <linux/init.h>
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#include <linux/resource.h>
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#include <linux/notifier.h>
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#include <linux/suspend.h>
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#include <linux/rwsem.h>
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#include <linux/ptrace.h>
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#include <linux/async.h>
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#include <linux/uaccess.h>
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#include <trace/events/module.h>
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/*
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* Assuming:
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*
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* threads = div64_u64((u64) totalram_pages * (u64) PAGE_SIZE,
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* (u64) THREAD_SIZE * 8UL);
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*
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* If you need less than 50 threads would mean we're dealing with systems
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* smaller than 3200 pages. This assuems you are capable of having ~13M memory,
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* and this would only be an be an upper limit, after which the OOM killer
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* would take effect. Systems like these are very unlikely if modules are
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* enabled.
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*/
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#define MAX_KMOD_CONCURRENT 50
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static atomic_t kmod_concurrent_max = ATOMIC_INIT(MAX_KMOD_CONCURRENT);
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static DECLARE_WAIT_QUEUE_HEAD(kmod_wq);
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/*
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* This is a restriction on having *all* MAX_KMOD_CONCURRENT threads
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* running at the same time without returning. When this happens we
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* believe you've somehow ended up with a recursive module dependency
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* creating a loop.
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*
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* We have no option but to fail.
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*
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* Userspace should proactively try to detect and prevent these.
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*/
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#define MAX_KMOD_ALL_BUSY_TIMEOUT 5
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/*
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modprobe_path is set via /proc/sys.
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*/
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char modprobe_path[KMOD_PATH_LEN] = "/sbin/modprobe";
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static void free_modprobe_argv(struct subprocess_info *info)
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{
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kfree(info->argv[3]); /* check call_modprobe() */
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kfree(info->argv);
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}
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static int call_modprobe(char *module_name, int wait)
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{
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struct subprocess_info *info;
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static char *envp[] = {
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"HOME=/",
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"TERM=linux",
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"PATH=/sbin:/usr/sbin:/bin:/usr/bin",
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NULL
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};
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char **argv = kmalloc(sizeof(char *[5]), GFP_KERNEL);
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if (!argv)
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goto out;
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module_name = kstrdup(module_name, GFP_KERNEL);
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if (!module_name)
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goto free_argv;
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argv[0] = modprobe_path;
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argv[1] = "-q";
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argv[2] = "--";
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argv[3] = module_name; /* check free_modprobe_argv() */
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argv[4] = NULL;
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info = call_usermodehelper_setup(modprobe_path, argv, envp, GFP_KERNEL,
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NULL, free_modprobe_argv, NULL);
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if (!info)
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goto free_module_name;
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return call_usermodehelper_exec(info, wait | UMH_KILLABLE);
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free_module_name:
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kfree(module_name);
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free_argv:
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kfree(argv);
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out:
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return -ENOMEM;
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}
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/**
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* __request_module - try to load a kernel module
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* @wait: wait (or not) for the operation to complete
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* @fmt: printf style format string for the name of the module
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* @...: arguments as specified in the format string
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*
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* Load a module using the user mode module loader. The function returns
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* zero on success or a negative errno code or positive exit code from
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* "modprobe" on failure. Note that a successful module load does not mean
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* the module did not then unload and exit on an error of its own. Callers
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* must check that the service they requested is now available not blindly
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* invoke it.
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*
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* If module auto-loading support is disabled then this function
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* simply returns -ENOENT.
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*/
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int __request_module(bool wait, const char *fmt, ...)
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{
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va_list args;
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char module_name[MODULE_NAME_LEN];
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int ret;
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/*
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* We don't allow synchronous module loading from async. Module
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* init may invoke async_synchronize_full() which will end up
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* waiting for this task which already is waiting for the module
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* loading to complete, leading to a deadlock.
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*/
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WARN_ON_ONCE(wait && current_is_async());
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if (!modprobe_path[0])
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return -ENOENT;
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va_start(args, fmt);
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ret = vsnprintf(module_name, MODULE_NAME_LEN, fmt, args);
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va_end(args);
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if (ret >= MODULE_NAME_LEN)
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return -ENAMETOOLONG;
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ret = security_kernel_module_request(module_name);
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if (ret)
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return ret;
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if (atomic_dec_if_positive(&kmod_concurrent_max) < 0) {
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pr_warn_ratelimited("request_module: kmod_concurrent_max (%u) close to 0 (max_modprobes: %u), for module %s, throttling...",
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atomic_read(&kmod_concurrent_max),
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MAX_KMOD_CONCURRENT, module_name);
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ret = wait_event_killable_timeout(kmod_wq,
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atomic_dec_if_positive(&kmod_concurrent_max) >= 0,
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MAX_KMOD_ALL_BUSY_TIMEOUT * HZ);
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if (!ret) {
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pr_warn_ratelimited("request_module: modprobe %s cannot be processed, kmod busy with %d threads for more than %d seconds now",
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module_name, MAX_KMOD_CONCURRENT, MAX_KMOD_ALL_BUSY_TIMEOUT);
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return -ETIME;
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} else if (ret == -ERESTARTSYS) {
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pr_warn_ratelimited("request_module: sigkill sent for modprobe %s, giving up", module_name);
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return ret;
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}
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}
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trace_module_request(module_name, wait, _RET_IP_);
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ret = call_modprobe(module_name, wait ? UMH_WAIT_PROC : UMH_WAIT_EXEC);
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atomic_inc(&kmod_concurrent_max);
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wake_up(&kmod_wq);
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return ret;
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}
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EXPORT_SYMBOL(__request_module);
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