Merge tag 'char-misc-4.14-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc

Pull char/misc driver fixes from Greg KH:
 "Here are four small fixes for 4.14-rc6.

  Three of them are binder driver fixes for reported issues, and the
  last one is a hyperv driver bugfix. Nothing major, but good fixes to
  get into 4.14-final.

  All of these have been in linux-next with no reported issues"

* tag 'char-misc-4.14-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc:
  android: binder: Fix null ptr dereference in debug msg
  android: binder: Don't get mm from task
  vmbus: hvsock: add proper sync for vmbus_hvsock_device_unregister()
  binder: call poll_wait() unconditionally.

4 files changed, 15 insertions, 26 deletions

diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index 0621a95b8597..fddf76ef5bd6 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -3662,12 +3662,6 @@ static void binder_stat_br(struct binder_proc *proc,
         }
 }
 
-static int binder_has_thread_work(struct binder_thread *thread)
-{
-        return !binder_worklist_empty(thread->proc, &thread->todo) ||
-                thread->looper_need_return;
-}
-
 static int binder_put_node_cmd(struct binder_proc *proc,
                                struct binder_thread *thread,
                                void __user **ptrp,
@@ -4297,12 +4291,9 @@ static unsigned int binder_poll(struct file *filp,
 
         binder_inner_proc_unlock(thread->proc);
 
-        if (binder_has_work(thread, wait_for_proc_work))
-                return POLLIN;
-
         poll_wait(filp, &thread->wait, wait);
 
-        if (binder_has_thread_work(thread))
+        if (binder_has_work(thread, wait_for_proc_work))
                 return POLLIN;
 
         return 0;
diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c
index 064f5e31ec55..c2819a3d58a6 100644
--- a/drivers/android/binder_alloc.c
+++ b/drivers/android/binder_alloc.c
@@ -215,17 +215,12 @@ static int binder_update_page_range(struct binder_alloc *alloc, int allocate,
                 }
         }
 
-        if (!vma && need_mm)
-                mm = get_task_mm(alloc->tsk);
+        if (!vma && need_mm && mmget_not_zero(alloc->vma_vm_mm))
+                mm = alloc->vma_vm_mm;
 
         if (mm) {
                 down_write(&mm->mmap_sem);
                 vma = alloc->vma;
-                if (vma && mm != alloc->vma_vm_mm) {
-                        pr_err("%d: vma mm and task mm mismatch\n",
-                                alloc->pid);
-                        vma = NULL;
-                }
         }
 
         if (!vma && need_mm) {
@@ -565,7 +560,7 @@ static void binder_delete_free_buffer(struct binder_alloc *alloc,
                 binder_alloc_debug(BINDER_DEBUG_BUFFER_ALLOC,
                                    "%d: merge free, buffer %pK do not share page with %pK or %pK\n",
                                    alloc->pid, buffer->data,
-                                   prev->data, next->data);
+                                   prev->data, next ? next->data : NULL);
                 binder_update_page_range(alloc, 0, buffer_start_page(buffer),
                                          buffer_start_page(buffer) + PAGE_SIZE,
                                          NULL);
@@ -720,6 +715,7 @@ int binder_alloc_mmap_handler(struct binder_alloc *alloc,
         barrier();
         alloc->vma = vma;
         alloc->vma_vm_mm = vma->vm_mm;
+        mmgrab(alloc->vma_vm_mm);
 
         return 0;
 
@@ -795,6 +791,8 @@ void binder_alloc_deferred_release(struct binder_alloc *alloc)
                 vfree(alloc->buffer);
         }
         mutex_unlock(&alloc->mutex);
+        if (alloc->vma_vm_mm)
+                mmdrop(alloc->vma_vm_mm);
 
         binder_alloc_debug(BINDER_DEBUG_OPEN_CLOSE,
                      "%s: %d buffers %d, pages %d\n",
@@ -889,7 +887,6 @@ int binder_alloc_get_allocated_count(struct binder_alloc *alloc)
 void binder_alloc_vma_close(struct binder_alloc *alloc)
 {
         WRITE_ONCE(alloc->vma, NULL);
-        WRITE_ONCE(alloc->vma_vm_mm, NULL);
 }
 
 /**
@@ -926,9 +923,9 @@ enum lru_status binder_alloc_free_page(struct list_head *item,
         page_addr = (uintptr_t)alloc->buffer + index * PAGE_SIZE;
         vma = alloc->vma;
         if (vma) {
-                mm = get_task_mm(alloc->tsk);
-                if (!mm)
-                        goto err_get_task_mm_failed;
+                if (!mmget_not_zero(alloc->vma_vm_mm))
+                        goto err_mmget;
+                mm = alloc->vma_vm_mm;
                 if (!down_write_trylock(&mm->mmap_sem))
                         goto err_down_write_mmap_sem_failed;
         }
@@ -963,7 +960,7 @@ enum lru_status binder_alloc_free_page(struct list_head *item,
 
 err_down_write_mmap_sem_failed:
         mmput_async(mm);
-err_get_task_mm_failed:
+err_mmget:
 err_page_already_freed:
         mutex_unlock(&alloc->mutex);
 err_get_alloc_mutex_failed:
@@ -1002,7 +999,6 @@ struct shrinker binder_shrinker = {
  */
 void binder_alloc_init(struct binder_alloc *alloc)
 {
-        alloc->tsk = current->group_leader;
         alloc->pid = current->group_leader->pid;
         mutex_init(&alloc->mutex);
         INIT_LIST_HEAD(&alloc->buffers);
diff --git a/drivers/android/binder_alloc.h b/drivers/android/binder_alloc.h
index a3a3602c689c..2dd33b6df104 100644
--- a/drivers/android/binder_alloc.h
+++ b/drivers/android/binder_alloc.h
@@ -100,7 +100,6 @@ struct binder_lru_page {
  */
 struct binder_alloc {
         struct mutex mutex;
-        struct task_struct *tsk;
         struct vm_area_struct *vma;
         struct mm_struct *vma_vm_mm;
         void *buffer;
diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
index 018d2e0f8ec5..379b0df123be 100644
--- a/drivers/hv/channel_mgmt.c
+++ b/drivers/hv/channel_mgmt.c
@@ -937,7 +937,10 @@ void vmbus_hvsock_device_unregister(struct vmbus_channel *channel)
 {
         BUG_ON(!is_hvsock_channel(channel));
 
-        channel->rescind = true;
+        /* We always get a rescind msg when a connection is closed. */
+        while (!READ_ONCE(channel->probe_done) || !READ_ONCE(channel->rescind))
+                msleep(1);
+
         vmbus_device_unregister(channel->device_obj);
 }
 EXPORT_SYMBOL_GPL(vmbus_hvsock_device_unregister);