1 files changed, 568 insertions, 0 deletions

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(&current->sighand->siglock);
+        flush_signal_handlers(current, 1);
+        spin_unlock_irq(&current->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,
+        },
+        { }
+};