[PATCH] ANDROID: binder: re-order some conditions

[PATCH] ANDROID: binder: re-order some conditions

[Dan Carpenter]

It doesn't make any difference to runtime but I've switched these two
checks to make my static checker happy.

The problem is that "buffer->data_size" is user controlled and if it's
less than "sizeo(*hdr)" then that means "offset" can be more than
"buffer->data_size".  It's just cleaner to check it in the other order.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>

diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index 764b63a5aade..00322b146469 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -2058,8 +2058,8 @@ static size_t binder_validate_object(struct binder_buffer *buffer, u64 offset)
 	struct binder_object_header *hdr;
 	size_t object_size = 0;
 
-	if (offset > buffer->data_size - sizeof(*hdr) ||
-	    buffer->data_size < sizeof(*hdr) ||
+	if (buffer->data_size < sizeof(*hdr) ||
+	    offset > buffer->data_size - sizeof(*hdr) ||
 	    !IS_ALIGNED(offset, sizeof(u32)))
 		return 0;
 

Re: [PATCH] ANDROID: binder: re-order some conditions

[Martijn Coenen]

On Thu, Mar 29, 2018 at 11:14 AM, Dan Carpenter
<dan.carpenter@oracle.com> wrote:
> It doesn't make any difference to runtime but I've switched these two
> checks to make my static checker happy.
>
> The problem is that "buffer->data_size" is user controlled and if it's
> less than "sizeo(*hdr)" then that means "offset" can be more than
> "buffer->data_size".  It's just cleaner to check it in the other order.
>
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Martijn Coenen <maco@android.com>

>
> diff --git a/drivers/android/binder.c b/drivers/android/binder.c
> index 764b63a5aade..00322b146469 100644
> --- a/drivers/android/binder.c
> +++ b/drivers/android/binder.c
> @@ -2058,8 +2058,8 @@ static size_t binder_validate_object(struct binder_buffer *buffer, u64 offset)
>         struct binder_object_header *hdr;
>         size_t object_size = 0;
>
> -       if (offset > buffer->data_size - sizeof(*hdr) ||
> -           buffer->data_size < sizeof(*hdr) ||
> +       if (buffer->data_size < sizeof(*hdr) ||
> +           offset > buffer->data_size - sizeof(*hdr) ||
>             !IS_ALIGNED(offset, sizeof(u32)))
>                 return 0;
>