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kernel/kmod.c
18.5 KB
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/* kmod, the new module loader (replaces kerneld) Kirk Petersen Reorganized not to be a daemon by Adam Richter, with guidance from Greg Zornetzer. Modified to avoid chroot and file sharing problems. Mikael Pettersson Limit the concurrent number of kmod modprobes to catch loops from "modprobe needs a service that is in a module". Keith Owens <kaos@ocs.com.au> December 1999 Unblock all signals when we exec a usermode process. Shuu Yamaguchi <shuu@wondernetworkresources.com> December 2000 call_usermodehelper wait flag, and remove exec_usermodehelper. Rusty Russell <rusty@rustcorp.com.au> Jan 2003 */ |
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#include <linux/module.h> #include <linux/sched.h> #include <linux/syscalls.h> #include <linux/unistd.h> #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> #include <linux/security.h> #include <linux/mount.h> #include <linux/kernel.h> #include <linux/init.h> |
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#include <linux/resource.h> |
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#include <linux/notifier.h> #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 <asm/uaccess.h> |
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#include <trace/events/module.h> |
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extern int max_threads; static struct workqueue_struct *khelper_wq; |
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#define CAP_BSET (void *)1 #define CAP_PI (void *)2 static kernel_cap_t usermodehelper_bset = CAP_FULL_SET; static kernel_cap_t usermodehelper_inheritable = CAP_FULL_SET; static DEFINE_SPINLOCK(umh_sysctl_lock); |
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static DECLARE_RWSEM(umhelper_sem); |
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|
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#ifdef CONFIG_MODULES |
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/* modprobe_path is set via /proc/sys. */ char modprobe_path[KMOD_PATH_LEN] = "/sbin/modprobe"; |
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static void free_modprobe_argv(struct subprocess_info *info) { kfree(info->argv[3]); /* check call_modprobe() */ kfree(info->argv); } |
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static int call_modprobe(char *module_name, int wait) { |
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struct subprocess_info *info; |
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static char *envp[] = { "HOME=/", "TERM=linux", "PATH=/sbin:/usr/sbin:/bin:/usr/bin", NULL }; |
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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; |
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|
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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); |
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free_argv: kfree(argv); out: return -ENOMEM; |
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} |
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/** |
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* __request_module - try to load a kernel module * @wait: wait (or not) for the operation to complete |
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* @fmt: printf style format string for the name of the module * @...: arguments as specified in the format string |
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* * Load a module using the user mode module loader. The function returns * zero on success or a negative errno code 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. */ |
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int __request_module(bool wait, const char *fmt, ...) |
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{ va_list args; char module_name[MODULE_NAME_LEN]; unsigned int max_modprobes; int ret; |
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static atomic_t kmod_concurrent = ATOMIC_INIT(0); #define MAX_KMOD_CONCURRENT 50 /* Completely arbitrary value - KAO */ static int kmod_loop_msg; |
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/* * 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()); |
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if (!modprobe_path[0]) return 0; |
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va_start(args, fmt); ret = vsnprintf(module_name, MODULE_NAME_LEN, fmt, args); va_end(args); if (ret >= MODULE_NAME_LEN) return -ENAMETOOLONG; |
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ret = security_kernel_module_request(module_name); if (ret) return ret; |
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/* If modprobe needs a service that is in a module, we get a recursive * loop. Limit the number of running kmod threads to max_threads/2 or * MAX_KMOD_CONCURRENT, whichever is the smaller. A cleaner method * would be to run the parents of this process, counting how many times * kmod was invoked. That would mean accessing the internals of the * process tables to get the command line, proc_pid_cmdline is static * and it is not worth changing the proc code just to handle this case. * KAO. * * "trace the ppid" is simple, but will fail if someone's * parent exits. I think this is as good as it gets. --RR */ max_modprobes = min(max_threads/2, MAX_KMOD_CONCURRENT); atomic_inc(&kmod_concurrent); if (atomic_read(&kmod_concurrent) > max_modprobes) { /* We may be blaming an innocent here, but unlikely */ |
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if (kmod_loop_msg < 5) { |
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printk(KERN_ERR "request_module: runaway loop modprobe %s ", module_name); |
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kmod_loop_msg++; } |
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atomic_dec(&kmod_concurrent); return -ENOMEM; } |
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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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|
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atomic_dec(&kmod_concurrent); return ret; } |
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EXPORT_SYMBOL(__request_module); |
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#endif /* CONFIG_MODULES */ |
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|
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static void call_usermodehelper_freeinfo(struct subprocess_info *info) { if (info->cleanup) (*info->cleanup)(info); kfree(info); } static void umh_complete(struct subprocess_info *sub_info) { struct completion *comp = xchg(&sub_info->complete, NULL); /* * See call_usermodehelper_exec(). If xchg() returns NULL * we own sub_info, the UMH_KILLABLE caller has gone away * or the caller used UMH_NO_WAIT. */ if (comp) complete(comp); else call_usermodehelper_freeinfo(sub_info); } |
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/* * This is the task which runs the usermode application */ static int ____call_usermodehelper(void *data) { struct subprocess_info *sub_info = data; |
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struct cred *new; |
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int retval; |
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spin_lock_irq(¤t->sighand->siglock); flush_signal_handlers(current, 1); |
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spin_unlock_irq(¤t->sighand->siglock); /* We can run anywhere, unlike our parent keventd(). */ |
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set_cpus_allowed_ptr(current, cpu_all_mask); |
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|
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/* * Our parent is keventd, which runs with elevated scheduling priority. * Avoid propagating that into the userspace child. */ set_user_nice(current, 0); |
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retval = -ENOMEM; new = prepare_kernel_cred(current); if (!new) |
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goto out; |
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spin_lock(&umh_sysctl_lock); new->cap_bset = cap_intersect(usermodehelper_bset, new->cap_bset); new->cap_inheritable = cap_intersect(usermodehelper_inheritable, new->cap_inheritable); spin_unlock(&umh_sysctl_lock); |
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if (sub_info->init) { retval = sub_info->init(sub_info, new); if (retval) { abort_creds(new); |
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goto out; |
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} } |
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commit_creds(new); |
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retval = do_execve(getname_kernel(sub_info->path), |
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(const char __user *const __user *)sub_info->argv, (const char __user *const __user *)sub_info->envp); |
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out: sub_info->retval = retval; /* wait_for_helper() will call umh_complete if UHM_WAIT_PROC. */ |
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if (!(sub_info->wait & UMH_WAIT_PROC)) |
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umh_complete(sub_info); |
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if (!retval) return 0; |
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do_exit(0); |
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} /* Keventd can't block, but this (a child) can. */ static int wait_for_helper(void *data) { struct subprocess_info *sub_info = data; pid_t pid; |
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|
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/* If SIGCLD is ignored sys_wait4 won't populate the status. */ |
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kernel_sigaction(SIGCHLD, SIG_DFL); |
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pid = kernel_thread(____call_usermodehelper, sub_info, SIGCHLD); if (pid < 0) { sub_info->retval = pid; } else { |
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int ret = -ECHILD; |
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/* * Normally it is bogus to call wait4() from in-kernel because * wait4() wants to write the exit code to a userspace address. * But wait_for_helper() always runs as keventd, and put_user() * to a kernel address works OK for kernel threads, due to their * having an mm_segment_t which spans the entire address space. * * Thus the __user pointer cast is valid here. */ |
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sys_wait4(pid, (int __user *)&ret, 0, NULL); /* * If ret is 0, either ____call_usermodehelper failed and the * real error code is already in sub_info->retval or * sub_info->retval is 0 anyway, so don't mess with it then. */ if (ret) sub_info->retval = ret; |
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} |
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umh_complete(sub_info); |
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do_exit(0); |
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} /* This is run by khelper thread */ |
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static void __call_usermodehelper(struct work_struct *work) |
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{ |
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struct subprocess_info *sub_info = container_of(work, struct subprocess_info, work); |
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pid_t pid; |
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|
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if (sub_info->wait & UMH_WAIT_PROC) |
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pid = kernel_thread(wait_for_helper, sub_info, CLONE_FS | CLONE_FILES | SIGCHLD); |
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else pid = kernel_thread(____call_usermodehelper, sub_info, SIGCHLD); |
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|
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if (pid < 0) { sub_info->retval = pid; |
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umh_complete(sub_info); |
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} |
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} |
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/* * 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). |
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* Should always be manipulated under umhelper_sem acquired for write. |
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*/ |
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static enum umh_disable_depth usermodehelper_disabled = UMH_DISABLED; |
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/* Number of helpers running */ static atomic_t running_helpers = ATOMIC_INIT(0); /* |
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* Wait queue head used by usermodehelper_disable() to wait for all running |
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* helpers to finish. */ static DECLARE_WAIT_QUEUE_HEAD(running_helpers_waitq); /* |
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* Used by usermodehelper_read_lock_wait() to wait for usermodehelper_disabled * to become 'false'. */ static DECLARE_WAIT_QUEUE_HEAD(usermodehelper_disabled_waitq); /* |
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* Time to wait for running_helpers to become zero before the setting of |
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* usermodehelper_disabled in usermodehelper_disable() fails |
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*/ #define RUNNING_HELPERS_TIMEOUT (5 * HZ) |
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int usermodehelper_read_trylock(void) |
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{ |
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DEFINE_WAIT(wait); |
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int ret = 0; |
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down_read(&umhelper_sem); |
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for (;;) { prepare_to_wait(&usermodehelper_disabled_waitq, &wait, TASK_INTERRUPTIBLE); if (!usermodehelper_disabled) break; if (usermodehelper_disabled == UMH_DISABLED) ret = -EAGAIN; |
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up_read(&umhelper_sem); |
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if (ret) break; schedule(); try_to_freeze(); down_read(&umhelper_sem); |
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} |
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finish_wait(&usermodehelper_disabled_waitq, &wait); |
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return ret; |
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} |
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EXPORT_SYMBOL_GPL(usermodehelper_read_trylock); |
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|
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long usermodehelper_read_lock_wait(long timeout) { DEFINE_WAIT(wait); if (timeout < 0) return -EINVAL; down_read(&umhelper_sem); for (;;) { prepare_to_wait(&usermodehelper_disabled_waitq, &wait, TASK_UNINTERRUPTIBLE); if (!usermodehelper_disabled) break; up_read(&umhelper_sem); timeout = schedule_timeout(timeout); if (!timeout) break; down_read(&umhelper_sem); } finish_wait(&usermodehelper_disabled_waitq, &wait); return timeout; } EXPORT_SYMBOL_GPL(usermodehelper_read_lock_wait); |
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void usermodehelper_read_unlock(void) |
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{ up_read(&umhelper_sem); } |
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EXPORT_SYMBOL_GPL(usermodehelper_read_unlock); |
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|
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/** |
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* __usermodehelper_set_disable_depth - Modify usermodehelper_disabled. |
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* @depth: New value to assign to usermodehelper_disabled. |
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* * Change the value of usermodehelper_disabled (under umhelper_sem locked for * writing) and wakeup tasks waiting for it to change. |
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*/ |
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void __usermodehelper_set_disable_depth(enum umh_disable_depth depth) |
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{ down_write(&umhelper_sem); |
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usermodehelper_disabled = depth; |
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wake_up(&usermodehelper_disabled_waitq); up_write(&umhelper_sem); } /** |
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* __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. |
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*/ |
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int __usermodehelper_disable(enum umh_disable_depth depth) |
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{ |
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long retval; |
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if (!depth) return -EINVAL; |
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down_write(&umhelper_sem); |
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usermodehelper_disabled = depth; |
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up_write(&umhelper_sem); |
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/* * From now on call_usermodehelper_exec() won't start any new * helpers, so it is sufficient if running_helpers turns out to * be zero at one point (it may be increased later, but that * doesn't matter). */ retval = wait_event_timeout(running_helpers_waitq, |
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atomic_read(&running_helpers) == 0, RUNNING_HELPERS_TIMEOUT); |
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if (retval) return 0; |
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|
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__usermodehelper_set_disable_depth(UMH_ENABLED); |
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return -EAGAIN; } |
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static void helper_lock(void) { atomic_inc(&running_helpers); |
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smp_mb__after_atomic(); |
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} static void helper_unlock(void) { if (atomic_dec_and_test(&running_helpers)) wake_up(&running_helpers_waitq); } |
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|
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/** |
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* call_usermodehelper_setup - prepare to call a usermode helper |
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* @path: path to usermode executable * @argv: arg vector for process * @envp: environment for process |
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* @gfp_mask: gfp mask for memory allocation |
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* @cleanup: a cleanup function * @init: an init function * @data: arbitrary context sensitive data |
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* |
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* Returns either %NULL on allocation failure, or a subprocess_info |
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* structure. This should be passed to call_usermodehelper_exec to * exec the process and free the structure. |
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* * 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 ethe 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. |
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*/ |
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struct subprocess_info *call_usermodehelper_setup(char *path, char **argv, |
938e4b22e usermodehelper: e... |
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char **envp, gfp_t gfp_mask, int (*init)(struct subprocess_info *info, struct cred *new), void (*cleanup)(struct subprocess_info *info), void *data) |
0ab4dc922 usermodehelper: s... |
477 478 |
{ struct subprocess_info *sub_info; |
ac331d158 call_usermodehelp... |
479 |
sub_info = kzalloc(sizeof(struct subprocess_info), gfp_mask); |
0ab4dc922 usermodehelper: s... |
480 481 482 483 484 485 486 |
if (!sub_info) goto out; INIT_WORK(&sub_info->work, __call_usermodehelper); sub_info->path = path; sub_info->argv = argv; sub_info->envp = envp; |
938e4b22e usermodehelper: e... |
487 488 489 490 |
sub_info->cleanup = cleanup; sub_info->init = init; sub_info->data = data; |
0ab4dc922 usermodehelper: s... |
491 492 493 |
out: return sub_info; } |
938e4b22e usermodehelper: e... |
494 |
EXPORT_SYMBOL(call_usermodehelper_setup); |
0ab4dc922 usermodehelper: s... |
495 496 |
/** |
0ab4dc922 usermodehelper: s... |
497 498 |
* call_usermodehelper_exec - start a usermode application * @sub_info: information about the subprocessa |
1da177e4c Linux-2.6.12-rc2 |
499 |
* @wait: wait for the application to finish and return status. |
66e5b7e19 kmod: remove call... |
500 501 |
* 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 |
a98f0dd34 [PATCH] x86-64: A... |
502 |
* from interrupt context. |
1da177e4c Linux-2.6.12-rc2 |
503 504 505 506 |
* * Runs a user-space application. The application is started * asynchronously if wait is not set, and runs as a child of keventd. * (ie. it runs with full root capabilities). |
1da177e4c Linux-2.6.12-rc2 |
507 |
*/ |
9d944ef32 usermodehelper: k... |
508 |
int call_usermodehelper_exec(struct subprocess_info *sub_info, int wait) |
1da177e4c Linux-2.6.12-rc2 |
509 |
{ |
60be6b9a4 [PATCH] lockdep: ... |
510 |
DECLARE_COMPLETION_ONSTACK(done); |
784680336 Fix unbalanced he... |
511 |
int retval = 0; |
1da177e4c Linux-2.6.12-rc2 |
512 |
|
4c1c7be95 kernel/kmod.c: ch... |
513 514 515 516 |
if (!sub_info->path) { call_usermodehelper_freeinfo(sub_info); return -EINVAL; } |
ccd4b65ae PM: prevent froze... |
517 |
helper_lock(); |
8cdd4936c PM: disable userm... |
518 |
if (!khelper_wq || usermodehelper_disabled) { |
0ab4dc922 usermodehelper: s... |
519 520 521 |
retval = -EBUSY; goto out; } |
0f20784d4 kmod: avoid deadl... |
522 |
/* |
0baf2a4db kernel/kmod: fix ... |
523 524 525 526 527 |
* Set the completion pointer only if there is a waiter. * This makes it possible to use umh_complete to free * the data structure in case of UMH_NO_WAIT. */ sub_info->complete = (wait == UMH_NO_WAIT) ? NULL : &done; |
a98f0dd34 [PATCH] x86-64: A... |
528 529 530 |
sub_info->wait = wait; queue_work(khelper_wq, &sub_info->work); |
784680336 Fix unbalanced he... |
531 532 |
if (wait == UMH_NO_WAIT) /* task has freed sub_info */ goto unlock; |
d0bd587a8 usermodehelper: i... |
533 534 535 536 537 538 539 540 541 542 543 |
if (wait & UMH_KILLABLE) { retval = wait_for_completion_killable(&done); if (!retval) goto wait_done; /* umh_complete() will see NULL and free sub_info */ if (xchg(&sub_info->complete, NULL)) goto unlock; /* fallthrough, umh_complete() was already called */ } |
1da177e4c Linux-2.6.12-rc2 |
544 |
wait_for_completion(&done); |
d0bd587a8 usermodehelper: i... |
545 |
wait_done: |
a98f0dd34 [PATCH] x86-64: A... |
546 |
retval = sub_info->retval; |
784680336 Fix unbalanced he... |
547 |
out: |
0ab4dc922 usermodehelper: s... |
548 |
call_usermodehelper_freeinfo(sub_info); |
784680336 Fix unbalanced he... |
549 |
unlock: |
ccd4b65ae PM: prevent froze... |
550 |
helper_unlock(); |
a98f0dd34 [PATCH] x86-64: A... |
551 |
return retval; |
1da177e4c Linux-2.6.12-rc2 |
552 |
} |
938e4b22e usermodehelper: e... |
553 |
EXPORT_SYMBOL(call_usermodehelper_exec); |
785042f2e kmod: move call_u... |
554 |
|
66e5b7e19 kmod: remove call... |
555 556 557 558 559 560 561 562 563 564 565 566 |
/** * 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(). |
79c743dd1 kernel/kmod.c: do... |
567 |
*/ |
66e5b7e19 kmod: remove call... |
568 |
int call_usermodehelper(char *path, char **argv, char **envp, int wait) |
785042f2e kmod: move call_u... |
569 570 571 |
{ struct subprocess_info *info; gfp_t gfp_mask = (wait == UMH_NO_WAIT) ? GFP_ATOMIC : GFP_KERNEL; |
938e4b22e usermodehelper: e... |
572 |
info = call_usermodehelper_setup(path, argv, envp, gfp_mask, |
66e5b7e19 kmod: remove call... |
573 |
NULL, NULL, NULL); |
785042f2e kmod: move call_u... |
574 575 |
if (info == NULL) return -ENOMEM; |
785042f2e kmod: move call_u... |
576 577 |
return call_usermodehelper_exec(info, wait); } |
66e5b7e19 kmod: remove call... |
578 |
EXPORT_SYMBOL(call_usermodehelper); |
1da177e4c Linux-2.6.12-rc2 |
579 |
|
17f60a7da capabilites: allo... |
580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 |
static int proc_cap_handler(struct ctl_table *table, int write, void __user *buffer, size_t *lenp, loff_t *ppos) { struct ctl_table t; unsigned long cap_array[_KERNEL_CAPABILITY_U32S]; kernel_cap_t new_cap; int err, i; if (write && (!capable(CAP_SETPCAP) || !capable(CAP_SYS_MODULE))) return -EPERM; /* * convert from the global kernel_cap_t to the ulong array to print to * userspace if this is a read. */ spin_lock(&umh_sysctl_lock); for (i = 0; i < _KERNEL_CAPABILITY_U32S; i++) { if (table->data == CAP_BSET) cap_array[i] = usermodehelper_bset.cap[i]; else if (table->data == CAP_PI) cap_array[i] = usermodehelper_inheritable.cap[i]; else BUG(); } spin_unlock(&umh_sysctl_lock); t = *table; t.data = &cap_array; /* * actually read or write and array of ulongs from userspace. Remember * these are least significant 32 bits first */ err = proc_doulongvec_minmax(&t, write, buffer, lenp, ppos); if (err < 0) return err; /* * convert from the sysctl array of ulongs to the kernel_cap_t * internal representation */ for (i = 0; i < _KERNEL_CAPABILITY_U32S; i++) new_cap.cap[i] = cap_array[i]; /* * Drop everything not in the new_cap (but don't add things) */ spin_lock(&umh_sysctl_lock); if (write) { if (table->data == CAP_BSET) usermodehelper_bset = cap_intersect(usermodehelper_bset, new_cap); if (table->data == CAP_PI) usermodehelper_inheritable = cap_intersect(usermodehelper_inheritable, new_cap); } spin_unlock(&umh_sysctl_lock); return 0; } struct ctl_table usermodehelper_table[] = { { .procname = "bset", .data = CAP_BSET, .maxlen = _KERNEL_CAPABILITY_U32S * sizeof(unsigned long), .mode = 0600, .proc_handler = proc_cap_handler, }, { .procname = "inheritable", .data = CAP_PI, .maxlen = _KERNEL_CAPABILITY_U32S * sizeof(unsigned long), .mode = 0600, .proc_handler = proc_cap_handler, }, { } }; |
1da177e4c Linux-2.6.12-rc2 |
657 658 659 660 661 |
void __init usermodehelper_init(void) { khelper_wq = create_singlethread_workqueue("khelper"); BUG_ON(!khelper_wq); } |