android: binder: fix type mismatch warning

Allowing binder to expose the 64-bit API on 32-bit kernels caused a
build warning:

drivers/android/binder.c: In function 'binder_transaction_buffer_release':
drivers/android/binder.c:2220:15: error: cast to pointer from integer of different size [-Werror=int-to-pointer-cast]
    fd_array = (u32 *)(parent_buffer + fda->parent_offset);
               ^
drivers/android/binder.c: In function 'binder_translate_fd_array':
drivers/android/binder.c:2445:13: error: cast to pointer from integer of different size [-Werror=int-to-pointer-cast]
  fd_array = (u32 *)(parent_buffer + fda->parent_offset);
             ^
drivers/android/binder.c: In function 'binder_fixup_parent':
drivers/android/binder.c:2511:18: error: cast to pointer from integer of different size [-Werror=int-to-pointer-cast]

This adds extra type casts to avoid the warning.

However, there is another problem with the Kconfig option: turning
it on or off creates two incompatible ABI versions, a kernel that
has this enabled cannot run user space that was built without it
or vice versa. A better solution might be to leave the option hidden
until the binder code is fixed to deal with both ABI versions.

Fixes: e8d2ed7d ("Revert "staging: Fix build issues with new binder API"")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/android/binder.c

@@ -2217,7 +2217,7 @@ static void binder_transaction_buffer_release(struct binder_proc *proc,
 				       debug_id, (u64)fda->num_fds);
 				continue;
 			}
-			fd_array = (u32 *)(parent_buffer + fda->parent_offset);
+			fd_array = (u32 *)(parent_buffer + (uintptr_t)fda->parent_offset);
 			for (fd_index = 0; fd_index < fda->num_fds; fd_index++)
 				task_close_fd(proc, fd_array[fd_index]);
 		} break;
@@ -2442,7 +2442,7 @@ static int binder_translate_fd_array(struct binder_fd_array_object *fda,
 	 */
 	parent_buffer = parent->buffer -
 		binder_alloc_get_user_buffer_offset(&target_proc->alloc);
-	fd_array = (u32 *)(parent_buffer + fda->parent_offset);
+	fd_array = (u32 *)(parent_buffer + (uintptr_t)fda->parent_offset);
 	if (!IS_ALIGNED((unsigned long)fd_array, sizeof(u32))) {
 		binder_user_error("%d:%d parent offset not aligned correctly.\n",
 				  proc->pid, thread->pid);
@@ -2508,7 +2508,7 @@ static int binder_fixup_parent(struct binder_transaction *t,
 				  proc->pid, thread->pid);
 		return -EINVAL;
 	}
-	parent_buffer = (u8 *)(parent->buffer -
+	parent_buffer = (u8 *)((uintptr_t)parent->buffer -
 			binder_alloc_get_user_buffer_offset(
 				&target_proc->alloc));
 	*(binder_uintptr_t *)(parent_buffer + bp->parent_offset) = bp->buffer;