diff options
Diffstat (limited to 'kernel/kmod.c')
-rw-r--r-- | kernel/kmod.c | 531 |
1 files changed, 531 insertions, 0 deletions
diff --git a/kernel/kmod.c b/kernel/kmod.c new file mode 100644 index 00000000..fabfe541 --- /dev/null +++ b/kernel/kmod.c @@ -0,0 +1,531 @@ +/* + 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 +*/ +#include <linux/module.h> +#include <linux/sched.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 <asm/uaccess.h> + +#include <trace/events/module.h> + +extern int max_threads; + +static struct workqueue_struct *khelper_wq; + +#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); + +#ifdef CONFIG_MODULES + +/* + modprobe_path is set via /proc/sys. +*/ +char modprobe_path[KMOD_PATH_LEN] = "/sbin/modprobe"; + +/** + * __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 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]; + unsigned int max_modprobes; + int ret; + char *argv[] = { modprobe_path, "-q", "--", module_name, NULL }; + static char *envp[] = { "HOME=/", + "TERM=linux", + "PATH=/sbin:/usr/sbin:/bin:/usr/bin", + NULL }; + static atomic_t kmod_concurrent = ATOMIC_INIT(0); +#define MAX_KMOD_CONCURRENT 50 /* Completely arbitrary value - KAO */ + static int kmod_loop_msg; + + 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 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 */ + if (kmod_loop_msg < 5) { + printk(KERN_ERR + "request_module: runaway loop modprobe %s\n", + module_name); + kmod_loop_msg++; + } + atomic_dec(&kmod_concurrent); + return -ENOMEM; + } + + trace_module_request(module_name, wait, _RET_IP_); + + ret = call_usermodehelper_fns(modprobe_path, argv, envp, + wait ? UMH_WAIT_PROC : UMH_WAIT_EXEC, + NULL, NULL, NULL); + + atomic_dec(&kmod_concurrent); + return ret; +} +EXPORT_SYMBOL(__request_module); +#endif /* CONFIG_MODULES */ + +/* + * This is the task which runs the usermode application + */ +static int ____call_usermodehelper(void *data) +{ + struct subprocess_info *sub_info = data; + struct cred *new; + int retval; + + spin_lock_irq(¤t->sighand->siglock); + flush_signal_handlers(current, 1); + spin_unlock_irq(¤t->sighand->siglock); + + /* We can run anywhere, unlike our parent keventd(). */ + set_cpus_allowed_ptr(current, cpu_all_mask); + + /* + * Our parent is keventd, which runs with elevated scheduling priority. + * Avoid propagating that into the userspace child. + */ + set_user_nice(current, 0); + + retval = -ENOMEM; + new = prepare_kernel_cred(current); + if (!new) + goto fail; + + 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); + + if (sub_info->init) { + retval = sub_info->init(sub_info, new); + if (retval) { + abort_creds(new); + goto fail; + } + } + + commit_creds(new); + + retval = kernel_execve(sub_info->path, + (const char *const *)sub_info->argv, + (const char *const *)sub_info->envp); + + /* Exec failed? */ +fail: + sub_info->retval = retval; + do_exit(0); +} + +void call_usermodehelper_freeinfo(struct subprocess_info *info) +{ + if (info->cleanup) + (*info->cleanup)(info); + kfree(info); +} +EXPORT_SYMBOL(call_usermodehelper_freeinfo); + +/* 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; + + /* If SIGCLD is ignored sys_wait4 won't populate the status. */ + spin_lock_irq(¤t->sighand->siglock); + current->sighand->action[SIGCHLD-1].sa.sa_handler = SIG_DFL; + spin_unlock_irq(¤t->sighand->siglock); + + pid = kernel_thread(____call_usermodehelper, sub_info, SIGCHLD); + if (pid < 0) { + sub_info->retval = pid; + } else { + int ret = -ECHILD; + /* + * 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. + */ + 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; + } + + complete(sub_info->complete); + return 0; +} + +/* This is run by khelper thread */ +static void __call_usermodehelper(struct work_struct *work) +{ + struct subprocess_info *sub_info = + container_of(work, struct subprocess_info, work); + enum umh_wait wait = sub_info->wait; + pid_t pid; + + /* CLONE_VFORK: wait until the usermode helper has execve'd + * successfully We need the data structures to stay around + * until that is done. */ + if (wait == UMH_WAIT_PROC) + pid = kernel_thread(wait_for_helper, sub_info, + CLONE_FS | CLONE_FILES | SIGCHLD); + else + pid = kernel_thread(____call_usermodehelper, sub_info, + CLONE_VFORK | SIGCHLD); + + switch (wait) { + case UMH_NO_WAIT: + call_usermodehelper_freeinfo(sub_info); + break; + + case UMH_WAIT_PROC: + if (pid > 0) + break; + /* FALLTHROUGH */ + case UMH_WAIT_EXEC: + if (pid < 0) + sub_info->retval = pid; + complete(sub_info->complete); + } +} + +/* + * 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). + */ +static int usermodehelper_disabled; + +/* Number of helpers running */ +static atomic_t running_helpers = ATOMIC_INIT(0); + +/* + * Wait queue head used by usermodehelper_pm_callback() to wait for all running + * helpers to finish. + */ +static DECLARE_WAIT_QUEUE_HEAD(running_helpers_waitq); + +/* + * Time to wait for running_helpers to become zero before the setting of + * usermodehelper_disabled in usermodehelper_pm_callback() fails + */ +#define RUNNING_HELPERS_TIMEOUT (5 * HZ) + +/** + * usermodehelper_disable - prevent new helpers from being started + */ +int usermodehelper_disable(void) +{ + long retval; + + usermodehelper_disabled = 1; + smp_mb(); + /* + * 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, + atomic_read(&running_helpers) == 0, + RUNNING_HELPERS_TIMEOUT); + if (retval) + return 0; + + usermodehelper_disabled = 0; + return -EAGAIN; +} + +/** + * usermodehelper_enable - allow new helpers to be started again + */ +void usermodehelper_enable(void) +{ + usermodehelper_disabled = 0; +} + +/** + * usermodehelper_is_disabled - check if new helpers are allowed to be started + */ +bool usermodehelper_is_disabled(void) +{ + return usermodehelper_disabled; +} +EXPORT_SYMBOL_GPL(usermodehelper_is_disabled); + +static void helper_lock(void) +{ + atomic_inc(&running_helpers); + smp_mb__after_atomic_inc(); +} + +static void helper_unlock(void) +{ + if (atomic_dec_and_test(&running_helpers)) + wake_up(&running_helpers_waitq); +} + +/** + * 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 + * + * 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. + */ +struct subprocess_info *call_usermodehelper_setup(char *path, char **argv, + char **envp, gfp_t gfp_mask) +{ + struct subprocess_info *sub_info; + sub_info = kzalloc(sizeof(struct subprocess_info), gfp_mask); + if (!sub_info) + goto out; + + INIT_WORK(&sub_info->work, __call_usermodehelper); + sub_info->path = path; + sub_info->argv = argv; + sub_info->envp = envp; + out: + return sub_info; +} +EXPORT_SYMBOL(call_usermodehelper_setup); + +/** + * call_usermodehelper_setfns - set a cleanup/init function + * @info: a subprocess_info returned by call_usermodehelper_setup + * @cleanup: a cleanup function + * @init: an init function + * @data: arbitrary context sensitive data + * + * 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. + */ +void call_usermodehelper_setfns(struct subprocess_info *info, + int (*init)(struct subprocess_info *info, struct cred *new), + void (*cleanup)(struct subprocess_info *info), + void *data) +{ + info->cleanup = cleanup; + info->init = init; + info->data = data; +} +EXPORT_SYMBOL(call_usermodehelper_setfns); + +/** + * call_usermodehelper_exec - start a usermode application + * @sub_info: information about the subprocessa + * @wait: wait for the application to finish and return status. + * when -1 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 keventd. + * (ie. it runs with full root capabilities). + */ +int call_usermodehelper_exec(struct subprocess_info *sub_info, + enum umh_wait wait) +{ + DECLARE_COMPLETION_ONSTACK(done); + int retval = 0; + + helper_lock(); + if (sub_info->path[0] == '\0') + goto out; + + if (!khelper_wq || usermodehelper_disabled) { + retval = -EBUSY; + goto out; + } + + sub_info->complete = &done; + sub_info->wait = wait; + + queue_work(khelper_wq, &sub_info->work); + if (wait == UMH_NO_WAIT) /* task has freed sub_info */ + goto unlock; + wait_for_completion(&done); + retval = sub_info->retval; + +out: + call_usermodehelper_freeinfo(sub_info); +unlock: + helper_unlock(); + return retval; +} +EXPORT_SYMBOL(call_usermodehelper_exec); + +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, + }, + { } +}; + +void __init usermodehelper_init(void) +{ + khelper_wq = create_singlethread_workqueue("khelper"); + BUG_ON(!khelper_wq); +} |