releases/4.19.49/revert-binder-fix-handling-of-misaligned-binder-object.patch

From tkjos@android.com  Thu Jun  6 09:17:35 2019
From: Todd Kjos <tkjos@android.com>
Date: Wed,  5 Jun 2019 09:38:24 -0700
Subject: Revert "binder: fix handling of misaligned binder object"
To: tkjos@google.com, gregkh@linuxfoundation.org, stable@vger.kernel.org
Cc: ben.hutchings@codethink.co.uk, Alexander.Levin@microsoft.com
Message-ID: <20190605163825.178537-1-tkjos@google.com>

From: Todd Kjos <tkjos@android.com>

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>
---
 drivers/android/binder_alloc.c |   18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

--- a/drivers/android/binder_alloc.c
+++ b/drivers/android/binder_alloc.c
@@ -958,13 +958,14 @@ enum lru_status binder_alloc_free_page(s
 
 	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(s
 			       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);