[PATCH 4.14 1/2] Revert "binder: fix handling of misaligned binder object"

[Todd Kjos <tkjos@android.com>]

This reverts commit 33c6b9ca70a8b066a613e2a3d0331ae8f82aa31a.

The commit message is for a different patch. Reverting and then adding
the same patch back with the correct commit message.

Cc: stable <stable@vger.kernel.org> # 4.14
Signed-off-by: Todd Kjos <tkjos@google.com>
---
 drivers/android/binder_alloc.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c
index e0b0399ff7ec8..b9281f2725a6a 100644
--- a/drivers/android/binder_alloc.c
+++ b/drivers/android/binder_alloc.c
@@ -945,13 +945,14 @@ enum lru_status binder_alloc_free_page(struct list_head *item,
 
 	index = page - alloc->pages;
 	page_addr = (uintptr_t)alloc->buffer + index * PAGE_SIZE;
-
-	mm = alloc->vma_vm_mm;
-	if (!mmget_not_zero(mm))
-		goto err_mmget;
-	if (!down_write_trylock(&mm->mmap_sem))
-		goto err_down_write_mmap_sem_failed;
 	vma = binder_alloc_get_vma(alloc);
+	if (vma) {
+		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;
+	}
 
 	list_lru_isolate(lru, item);
 	spin_unlock(lock);
@@ -964,9 +965,10 @@ enum lru_status binder_alloc_free_page(struct list_head *item,
 			       PAGE_SIZE);
 
 		trace_binder_unmap_user_end(alloc, index);
+
+		up_write(&mm->mmap_sem);
+		mmput(mm);
 	}
-	up_write(&mm->mmap_sem);
-	mmput(mm);
 
 	trace_binder_unmap_kernel_start(alloc, index);
 
-- 
2.22.0.rc1.311.g5d7573a151-goog