diff options
| -rw-r--r-- | MAINTAINERS | 6 | ||||
| -rw-r--r-- | kernel/Makefile | 2 | ||||
| -rw-r--r-- | kernel/kmod.c | 560 | ||||
| -rw-r--r-- | kernel/umh.c | 568 |
4 files changed, 577 insertions, 559 deletions
diff --git a/MAINTAINERS b/MAINTAINERS index 9fe33e689c88..6a57fac2bd07 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -7457,6 +7457,12 @@ S: Maintained F: tools/testing/selftests/ F: Documentation/dev-tools/kselftest* +KERNEL USERMODE HELPER +M: "Luis R. Rodriguez" <mcgrof@kernel.org> +L: linux-kernel@vger.kernel.org +S: Maintained +F: kernel/umh.c + KERNEL VIRTUAL MACHINE (KVM) M: Paolo Bonzini <pbonzini@redhat.com> M: Radim Krčmář <rkrcmar@redhat.com> diff --git a/kernel/Makefile b/kernel/Makefile index 9c323a6daa46..44abbb0104b6 100644 --- a/kernel/Makefile +++ b/kernel/Makefile @@ -5,7 +5,7 @@ obj-y = fork.o exec_domain.o panic.o \ cpu.o exit.o softirq.o resource.o \ sysctl.o sysctl_binary.o capability.o ptrace.o user.o \ - signal.o sys.o kmod.o workqueue.o pid.o task_work.o \ + signal.o sys.o umh.o kmod.o workqueue.o pid.o task_work.o \ extable.o params.o \ kthread.o sys_ni.o nsproxy.o \ notifier.o ksysfs.o cred.o reboot.o \ diff --git a/kernel/kmod.c b/kernel/kmod.c index 2f37acde640b..cdff52974d18 100644 --- a/kernel/kmod.c +++ b/kernel/kmod.c @@ -1,23 +1,6 @@ /* - 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 -*/ + * kmod - the kernel module loader + */ #include <linux/module.h> #include <linux/sched.h> #include <linux/sched/task.h> @@ -45,14 +28,6 @@ #include <trace/events/module.h> -#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 /* * Assuming: @@ -204,534 +179,3 @@ int __request_module(bool wait, const char *fmt, ...) EXPORT_SYMBOL(__request_module); #endif /* CONFIG_MODULES */ - -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); -} - -/* - * This is the task which runs the usermode application - */ -static int call_usermodehelper_exec_async(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); - - /* - * Our parent (unbound workqueue) 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 out; - - 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 out; - } - } - - commit_creds(new); - - retval = do_execve(getname_kernel(sub_info->path), - (const char __user *const __user *)sub_info->argv, - (const char __user *const __user *)sub_info->envp); -out: - sub_info->retval = retval; - /* - * call_usermodehelper_exec_sync() will call umh_complete - * if UHM_WAIT_PROC. - */ - if (!(sub_info->wait & UMH_WAIT_PROC)) - umh_complete(sub_info); - if (!retval) - return 0; - do_exit(0); -} - -/* Handles UMH_WAIT_PROC. */ -static void call_usermodehelper_exec_sync(struct subprocess_info *sub_info) -{ - pid_t pid; - - /* If SIGCLD is ignored sys_wait4 won't populate the status. */ - kernel_sigaction(SIGCHLD, SIG_DFL); - pid = kernel_thread(call_usermodehelper_exec_async, 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 call_usermodehelper_exec_sync() always runs as kernel - * thread (workqueue) 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_exec_async 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; - } - - /* Restore default kernel sig handler */ - kernel_sigaction(SIGCHLD, SIG_IGN); - - umh_complete(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) -{ - struct subprocess_info *sub_info = - container_of(work, struct subprocess_info, work); - - if (sub_info->wait & UMH_WAIT_PROC) { - call_usermodehelper_exec_sync(sub_info); - } else { - pid_t pid; - /* - * Use CLONE_PARENT to reparent it to kthreadd; we do not - * want to pollute current->children, and we need a parent - * that always ignores SIGCHLD to ensure auto-reaping. - */ - pid = kernel_thread(call_usermodehelper_exec_async, sub_info, - CLONE_PARENT | SIGCHLD); - if (pid < 0) { - sub_info->retval = pid; - umh_complete(sub_info); - } - } -} - -/* - * 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 = UMH_DISABLED; - -/* Number of helpers running */ -static atomic_t running_helpers = ATOMIC_INIT(0); - -/* - * 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 (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. - * @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) -{ - long retval; - - 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 - * 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_set_disable_depth(UMH_ENABLED); - return -EAGAIN; -} - -static void helper_lock(void) -{ - atomic_inc(&running_helpers); - smp_mb__after_atomic(); -} - -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 - * @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(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) -{ - 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_exec_work); - -#ifdef CONFIG_STATIC_USERMODEHELPER - sub_info->path = CONFIG_STATIC_USERMODEHELPER_PATH; -#else - sub_info->path = path; -#endif - 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_exec - start a usermode application - * @sub_info: information about the subprocessa - * @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). - */ -int call_usermodehelper_exec(struct subprocess_info *sub_info, int wait) -{ - DECLARE_COMPLETION_ONSTACK(done); - int retval = 0; - - if (!sub_info->path) { - call_usermodehelper_freeinfo(sub_info); - return -EINVAL; - } - helper_lock(); - if (usermodehelper_disabled) { - retval = -EBUSY; - goto out; - } - - /* - * If there is no binary for us to call, then just return and get out of - * here. This allows us to set STATIC_USERMODEHELPER_PATH to "" and - * disable all call_usermodehelper() calls. - */ - if (strlen(sub_info->path) == 0) - goto out; - - /* - * 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; - sub_info->wait = wait; - - queue_work(system_unbound_wq, &sub_info->work); - if (wait == UMH_NO_WAIT) /* task has freed sub_info */ - goto unlock; - - 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 */ - } - - wait_for_completion(&done); -wait_done: - retval = sub_info->retval; -out: - call_usermodehelper_freeinfo(sub_info); -unlock: - helper_unlock(); - return retval; -} -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(const 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) -{ - 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, - }, - { } -}; diff --git a/kernel/umh.c b/kernel/umh.c new file mode 100644 index 000000000000..6ff9905250ff --- /dev/null +++ b/kernel/umh.c @@ -0,0 +1,568 @@ +/* + * 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/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> + +#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); + +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); +} + +/* + * This is the task which runs the usermode application + */ +static int call_usermodehelper_exec_async(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); + + /* + * Our parent (unbound workqueue) 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 out; + + 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 out; + } + } + + commit_creds(new); + + retval = do_execve(getname_kernel(sub_info->path), + (const char __user *const __user *)sub_info->argv, + (const char __user *const __user *)sub_info->envp); +out: + sub_info->retval = retval; + /* + * call_usermodehelper_exec_sync() will call umh_complete + * if UHM_WAIT_PROC. + */ + if (!(sub_info->wait & UMH_WAIT_PROC)) + umh_complete(sub_info); + if (!retval) + return 0; + do_exit(0); +} + +/* Handles UMH_WAIT_PROC. */ +static void call_usermodehelper_exec_sync(struct subprocess_info *sub_info) +{ + pid_t pid; + + /* If SIGCLD is ignored sys_wait4 won't populate the status. */ + kernel_sigaction(SIGCHLD, SIG_DFL); + pid = kernel_thread(call_usermodehelper_exec_async, 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 call_usermodehelper_exec_sync() always runs as kernel + * thread (workqueue) 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_exec_async 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; + } + + /* Restore default kernel sig handler */ + kernel_sigaction(SIGCHLD, SIG_IGN); + + umh_complete(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) +{ + struct subprocess_info *sub_info = + container_of(work, struct subprocess_info, work); + + if (sub_info->wait & UMH_WAIT_PROC) { + call_usermodehelper_exec_sync(sub_info); + } else { + pid_t pid; + /* + * Use CLONE_PARENT to reparent it to kthreadd; we do not + * want to pollute current->children, and we need a parent + * that always ignores SIGCHLD to ensure auto-reaping. + */ + pid = kernel_thread(call_usermodehelper_exec_async, sub_info, + CLONE_PARENT | SIGCHLD); + if (pid < 0) { + sub_info->retval = pid; + umh_complete(sub_info); + } + } +} + +/* + * 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 = UMH_DISABLED; + +/* Number of helpers running */ +static atomic_t running_helpers = ATOMIC_INIT(0); + +/* + * 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 (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. + * @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) +{ + long retval; + + 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 + * 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_set_disable_depth(UMH_ENABLED); + return -EAGAIN; +} + +static void helper_lock(void) +{ + atomic_inc(&running_helpers); + smp_mb__after_atomic(); +} + +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 + * @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(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) +{ + 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_exec_work); + +#ifdef CONFIG_STATIC_USERMODEHELPER + sub_info->path = CONFIG_STATIC_USERMODEHELPER_PATH; +#else + sub_info->path = path; +#endif + 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_exec - start a usermode application + * @sub_info: information about the subprocessa + * @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). + */ +int call_usermodehelper_exec(struct subprocess_info *sub_info, int wait) +{ + DECLARE_COMPLETION_ONSTACK(done); + int retval = 0; + + if (!sub_info->path) { + call_usermodehelper_freeinfo(sub_info); + return -EINVAL; + } + helper_lock(); + if (usermodehelper_disabled) { + retval = -EBUSY; + goto out; + } + + /* + * If there is no binary for us to call, then just return and get out of + * here. This allows us to set STATIC_USERMODEHELPER_PATH to "" and + * disable all call_usermodehelper() calls. + */ + if (strlen(sub_info->path) == 0) + goto out; + + /* + * 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; + sub_info->wait = wait; + + queue_work(system_unbound_wq, &sub_info->work); + if (wait == UMH_NO_WAIT) /* task has freed sub_info */ + goto unlock; + + 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 */ + } + + wait_for_completion(&done); +wait_done: + retval = sub_info->retval; +out: + call_usermodehelper_freeinfo(sub_info); +unlock: + helper_unlock(); + return retval; +} +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(const 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) +{ + 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, + }, + { } +}; |