Revert "binder: fix handling of misaligned binder object"

This reverts commit 6bf7d3c5c0c5dad650bfc4345ed553c18b69d59e.

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

Reported-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Cc: stable <stable@vger.kernel.org> # 4.19
Signed-off-by: Todd Kjos <tkjos@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c
index a654ccf..030c98f 100644 (file)
--- a/drivers/android/binder_alloc.c
+++ b/drivers/android/binder_alloc.c
@@ -958,13 +958,14 @@ 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);
@@ -977,9 +978,10 @@ 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);