cregit-Linux how code gets into the kernel

Release 4.15 kernel/kmod.c

Directory: kernel
 * 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.


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.


        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); }


Oleg Nesterov29100.00%1100.00%

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; }


Oleg Nesterov13780.12%266.67%
Lucas De Marchi3419.88%133.33%

/** * __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; }


Luis R. Rodriguez8237.10%316.67%
Linus Torvalds4419.91%15.56%
Rusty Russell209.05%211.11%
Linus Torvalds (pre-git)167.24%422.22%
Eric Paris146.33%15.56%
Oleg Nesterov135.88%211.11%
Li Zefan94.07%15.56%
Arjan van de Ven94.07%15.56%
Tejun Heo94.07%15.56%
Ingo Molnar31.36%15.56%
Jiri Kosina20.90%15.56%


Overall Contributors

Oleg Nesterov17933.33%36.98%
Luis R. Rodriguez10820.11%49.30%
Linus Torvalds5410.06%511.63%
Linus Torvalds (pre-git)387.08%613.95%
Lucas De Marchi346.33%12.33%
Rusty Russell234.28%24.65%
Eric Paris173.17%24.65%
Tejun Heo122.23%12.33%
Li Zefan122.23%12.33%
Andrew Morton112.05%36.98%
Arjan van de Ven101.86%12.33%
Ingo Molnar101.86%49.30%
Al Viro61.12%24.65%
Rafael J. Wysocki61.12%12.33%
Greg Kroah-Hartman30.56%12.33%
Christoph Hellwig30.56%12.33%
Srivatsa S. Bhat30.56%12.33%
Andi Kleen30.56%12.33%
Jiri Kosina20.37%12.33%
Matthew Wilcox20.37%12.33%
Neil Brown10.19%12.33%
Directory: kernel
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