diff options
Diffstat (limited to 'kernel/kmod.c')
| -rw-r--r-- | kernel/kmod.c | 303 |
1 files changed, 219 insertions, 84 deletions
diff --git a/kernel/kmod.c b/kernel/kmod.c index a16dac13576..8637e041a24 100644 --- a/kernel/kmod.c +++ b/kernel/kmod.c @@ -36,6 +36,9 @@ #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 <asm/uaccess.h> #include <trace/events/module.h> @@ -44,12 +47,20 @@ extern int max_threads; static struct workqueue_struct *khelper_wq; +/* + * kmod_thread_locker is used for deadlock avoidance. There is no explicit + * locking to protect this global - it is private to the singleton khelper + * thread and should only ever be modified by that thread. + */ +static const struct task_struct *kmod_thread_locker; + #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); +static DECLARE_RWSEM(umhelper_sem); #ifdef CONFIG_MODULES @@ -66,6 +77,7 @@ static void free_modprobe_argv(struct subprocess_info *info) static int call_modprobe(char *module_name, int wait) { + struct subprocess_info *info; static char *envp[] = { "HOME=/", "TERM=linux", @@ -87,8 +99,15 @@ static int call_modprobe(char *module_name, int wait) argv[3] = module_name; /* check free_modprobe_argv() */ argv[4] = NULL; - return call_usermodehelper_fns(modprobe_path, argv, envp, - wait | UMH_KILLABLE, NULL, free_modprobe_argv, 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: @@ -120,6 +139,17 @@ int __request_module(bool wait, const char *fmt, ...) #define MAX_KMOD_CONCURRENT 50 /* Completely arbitrary value - KAO */ static int kmod_loop_msg; + /* + * 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); @@ -209,23 +239,31 @@ static int ____call_usermodehelper(void *data) commit_creds(new); - retval = kernel_execve(sub_info->path, - (const char *const *)sub_info->argv, - (const char *const *)sub_info->envp); + retval = do_execve(getname_kernel(sub_info->path), + (const char __user *const __user *)sub_info->argv, + (const char __user *const __user *)sub_info->envp); + if (!retval) + return 0; /* Exec failed? */ fail: sub_info->retval = retval; - return 0; + do_exit(0); } -void call_usermodehelper_freeinfo(struct subprocess_info *info) +static int call_helper(void *data) +{ + /* Worker thread started blocking khelper thread. */ + kmod_thread_locker = current; + return ____call_usermodehelper(data); +} + +static void call_usermodehelper_freeinfo(struct subprocess_info *info) { if (info->cleanup) (*info->cleanup)(info); kfree(info); } -EXPORT_SYMBOL(call_usermodehelper_freeinfo); static void umh_complete(struct subprocess_info *sub_info) { @@ -247,10 +285,7 @@ static int wait_for_helper(void *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); - + kernel_sigaction(SIGCHLD, SIG_DFL); pid = kernel_thread(____call_usermodehelper, sub_info, SIGCHLD); if (pid < 0) { sub_info->retval = pid; @@ -277,7 +312,7 @@ static int wait_for_helper(void *data) } umh_complete(sub_info); - return 0; + do_exit(0); } /* This is run by khelper thread */ @@ -285,21 +320,21 @@ 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; + int wait = sub_info->wait & ~UMH_KILLABLE; pid_t pid; - if (wait != UMH_NO_WAIT) - wait &= ~UMH_KILLABLE; - /* 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, + else { + pid = kernel_thread(call_helper, sub_info, CLONE_VFORK | SIGCHLD); + /* Worker thread stopped blocking khelper thread. */ + kmod_thread_locker = NULL; + } switch (wait) { case UMH_NO_WAIT: @@ -321,33 +356,126 @@ static void __call_usermodehelper(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 int usermodehelper_disabled = 1; +static enum umh_disable_depth usermodehelper_disabled = UMH_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 + * 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_pm_callback() fails + * usermodehelper_disabled in usermodehelper_disable() fails */ #define RUNNING_HELPERS_TIMEOUT (5 * HZ) +int usermodehelper_read_trylock(void) +{ + DEFINE_WAIT(wait); + int ret = 0; + + down_read(&umhelper_sem); + for (;;) { + prepare_to_wait(&usermodehelper_disabled_waitq, &wait, + TASK_INTERRUPTIBLE); + if (!usermodehelper_disabled) + break; + + if (usermodehelper_disabled == UMH_DISABLED) + ret = -EAGAIN; + + up_read(&umhelper_sem); + + if (ret) + break; + + schedule(); + try_to_freeze(); + + down_read(&umhelper_sem); + } + finish_wait(&usermodehelper_disabled_waitq, &wait); + return ret; +} +EXPORT_SYMBOL_GPL(usermodehelper_read_trylock); + +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); + +void usermodehelper_read_unlock(void) +{ + up_read(&umhelper_sem); +} +EXPORT_SYMBOL_GPL(usermodehelper_read_unlock); + +/** + * __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) +{ + down_write(&umhelper_sem); + usermodehelper_disabled = depth; + wake_up(&usermodehelper_disabled_waitq); + up_write(&umhelper_sem); +} + /** - * usermodehelper_disable - prevent new helpers from being started + * __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(void) +int __usermodehelper_disable(enum umh_disable_depth depth) { long retval; - usermodehelper_disabled = 1; - smp_mb(); + if (!depth) + return -EINVAL; + + down_write(&umhelper_sem); + usermodehelper_disabled = depth; + up_write(&umhelper_sem); + /* * From now on call_usermodehelper_exec() won't start any new * helpers, so it is sufficient if running_helpers turns out to @@ -360,31 +488,14 @@ int usermodehelper_disable(void) if (retval) return 0; - usermodehelper_disabled = 0; + __usermodehelper_set_disable_depth(UMH_ENABLED); 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(); + smp_mb__after_atomic(); } static void helper_unlock(void) @@ -399,13 +510,28 @@ static void helper_unlock(void) * @argv: arg vector for process * @envp: environment for process * @gfp_mask: gfp mask for memory allocation + * @cleanup: a cleanup function + * @init: an init 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 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. */ struct subprocess_info *call_usermodehelper_setup(char *path, char **argv, - char **envp, gfp_t gfp_mask) + char **envp, gfp_t gfp_mask, + int (*init)(struct subprocess_info *info, struct cred *new), + void (*cleanup)(struct subprocess_info *info), + void *data) { struct subprocess_info *sub_info; sub_info = kzalloc(sizeof(struct subprocess_info), gfp_mask); @@ -416,69 +542,51 @@ struct subprocess_info *call_usermodehelper_setup(char *path, char **argv, sub_info->path = path; sub_info->argv = argv; sub_info->envp = envp; + + sub_info->cleanup = cleanup; + sub_info->init = init; + sub_info->data = data; 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 + * 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 keventd. * (ie. it runs with full root capabilities). */ -int call_usermodehelper_exec(struct subprocess_info *sub_info, - enum umh_wait wait) +int call_usermodehelper_exec(struct subprocess_info *sub_info, int wait) { DECLARE_COMPLETION_ONSTACK(done); int retval = 0; - helper_lock(); if (!sub_info->path) { - retval = -EINVAL; - goto out; + call_usermodehelper_freeinfo(sub_info); + return -EINVAL; } - - if (sub_info->path[0] == '\0') - goto out; - + helper_lock(); if (!khelper_wq || usermodehelper_disabled) { retval = -EBUSY; goto out; } + /* + * Worker thread must not wait for khelper thread at below + * wait_for_completion() if the thread was created with CLONE_VFORK + * flag, for khelper thread is already waiting for the thread at + * wait_for_completion() in do_fork(). + */ + if (wait != UMH_NO_WAIT && current == kmod_thread_locker) { + retval = -EBUSY; + goto out; + } sub_info->complete = &done; sub_info->wait = wait; @@ -509,6 +617,33 @@ unlock: } EXPORT_SYMBOL(call_usermodehelper_exec); +/** + * 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(char *path, char **argv, char **envp, int wait) +{ + struct subprocess_info *info; + gfp_t gfp_mask = (wait == UMH_NO_WAIT) ? GFP_ATOMIC : GFP_KERNEL; + + info = call_usermodehelper_setup(path, argv, envp, gfp_mask, + NULL, NULL, NULL); + if (info == NULL) + return -ENOMEM; + + return call_usermodehelper_exec(info, wait); +} +EXPORT_SYMBOL(call_usermodehelper); + static int proc_cap_handler(struct ctl_table *table, int write, void __user *buffer, size_t *lenp, loff_t *ppos) { |