// SPDX-License-Identifier: GPL-2.0-only /* * umh - the kernel usermode helper */ #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/fs_struct.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 <linux/initrd.h> #include <linux/freezer.h> #include <trace/events/module.h> static kernel_cap_t usermodehelper_bset = …; static kernel_cap_t usermodehelper_inheritable = …; static DEFINE_SPINLOCK(umh_sysctl_lock); static DECLARE_RWSEM(umhelper_sem); static void call_usermodehelper_freeinfo(struct subprocess_info *info) { … } static void umh_complete(struct subprocess_info *sub_info) { … } /* * This is the task which runs the usermode application */ static int call_usermodehelper_exec_async(void *data) { … } /* Handles UMH_WAIT_PROC. */ static void call_usermodehelper_exec_sync(struct subprocess_info *sub_info) { … } /* * We need to create the usermodehelper kernel thread from a task that is affine * to an optimized set of CPUs (or nohz housekeeping ones) such that they * inherit a widest affinity irrespective of call_usermodehelper() callers with * possibly reduced affinity (eg: per-cpu workqueues). We don't want * usermodehelper targets to contend a busy CPU. * * Unbound workqueues provide such wide affinity and allow to block on * UMH_WAIT_PROC requests without blocking pending request (up to some limit). * * Besides, workqueues provide the privilege level that caller might not have * to perform the usermodehelper request. * */ static void call_usermodehelper_exec_work(struct work_struct *work) { … } /* * If set, call_usermodehelper_exec() will exit immediately returning -EBUSY * (used for preventing user land processes from being created after the user * land has been frozen during a system-wide hibernation or suspend operation). * Should always be manipulated under umhelper_sem acquired for write. */ static enum umh_disable_depth usermodehelper_disabled = …; /* Number of helpers running */ static atomic_t running_helpers = …; /* * Wait queue head used by usermodehelper_disable() to wait for all running * helpers to finish. */ static DECLARE_WAIT_QUEUE_HEAD(running_helpers_waitq); /* * Used by usermodehelper_read_lock_wait() to wait for usermodehelper_disabled * to become 'false'. */ static DECLARE_WAIT_QUEUE_HEAD(usermodehelper_disabled_waitq); /* * Time to wait for running_helpers to become zero before the setting of * usermodehelper_disabled in usermodehelper_disable() fails */ #define RUNNING_HELPERS_TIMEOUT … int usermodehelper_read_trylock(void) { … } EXPORT_SYMBOL_GPL(…); long usermodehelper_read_lock_wait(long timeout) { … } EXPORT_SYMBOL_GPL(…); void usermodehelper_read_unlock(void) { … } EXPORT_SYMBOL_GPL(…); /** * __usermodehelper_set_disable_depth - Modify usermodehelper_disabled. * @depth: New value to assign to usermodehelper_disabled. * * Change the value of usermodehelper_disabled (under umhelper_sem locked for * writing) and wakeup tasks waiting for it to change. */ void __usermodehelper_set_disable_depth(enum umh_disable_depth depth) { … } /** * __usermodehelper_disable - Prevent new helpers from being started. * @depth: New value to assign to usermodehelper_disabled. * * Set usermodehelper_disabled to @depth and wait for running helpers to exit. */ int __usermodehelper_disable(enum umh_disable_depth depth) { … } static void helper_lock(void) { … } static void helper_unlock(void) { … } /** * call_usermodehelper_setup - prepare to call a usermode helper * @path: path to usermode executable * @argv: arg vector for process * @envp: environment for process * @gfp_mask: gfp mask for memory allocation * @init: an init function * @cleanup: a cleanup function * @data: arbitrary context sensitive data * * Returns either %NULL on allocation failure, or a subprocess_info * structure. This should be passed to call_usermodehelper_exec to * exec the process and free the structure. * * The init function is used to customize the helper process prior to * exec. A non-zero return code causes the process to error out, exit, * and return the failure to the calling process * * The cleanup function is just before the subprocess_info is about to * be freed. This can be used for freeing the argv and envp. The * Function must be runnable in either a process context or the * context in which call_usermodehelper_exec is called. */ struct subprocess_info *call_usermodehelper_setup(const char *path, char **argv, char **envp, gfp_t gfp_mask, int (*init)(struct subprocess_info *info, struct cred *new), void (*cleanup)(struct subprocess_info *info), void *data) { … } EXPORT_SYMBOL(…); /** * call_usermodehelper_exec - start a usermode application * @sub_info: information about the subprocess * @wait: wait for the application to finish and return status. * when UMH_NO_WAIT don't wait at all, but you get no useful error back * when the program couldn't be exec'ed. This makes it safe to call * from interrupt context. * * Runs a user-space application. The application is started * asynchronously if wait is not set, and runs as a child of system workqueues. * (ie. it runs with full root capabilities and optimized affinity). * * Note: successful return value does not guarantee the helper was called at * all. You can't rely on sub_info->{init,cleanup} being called even for * UMH_WAIT_* wait modes as STATIC_USERMODEHELPER_PATH="" turns all helpers * into a successful no-op. */ int call_usermodehelper_exec(struct subprocess_info *sub_info, int wait) { … } EXPORT_SYMBOL(…); /** * call_usermodehelper() - prepare and start a usermode application * @path: path to usermode executable * @argv: arg vector for process * @envp: environment for process * @wait: wait for the application to finish and return status. * when UMH_NO_WAIT don't wait at all, but you get no useful error back * when the program couldn't be exec'ed. This makes it safe to call * from interrupt context. * * This function is the equivalent to use call_usermodehelper_setup() and * call_usermodehelper_exec(). */ int call_usermodehelper(const char *path, char **argv, char **envp, int wait) { … } EXPORT_SYMBOL(…); #if defined(CONFIG_SYSCTL) static int proc_cap_handler(const struct ctl_table *table, int write, void *buffer, size_t *lenp, loff_t *ppos) { … } static struct ctl_table usermodehelper_table[] = …; static int __init init_umh_sysctls(void) { … } early_initcall(init_umh_sysctls); #endif /* CONFIG_SYSCTL */
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