Re: [PATCH] zsmalloc: don't underflow size calculation in zs_obj_write()

[Sergey Senozhatsky <senozhatsky@chromium.org>]

On (25/05/04 20:00), Sergey Senozhatsky wrote:
> Do not mix class->size and object size during offsets/sizes
> calculation in zs_obj_write().  Size classes can merge into
> clusters, based on objects-per-zspage and pages-per-zspage
> characteristics, so some size classes can store objects
> smaller than class->size.  This becomes problematic when
> object size is much smaller than class->size - we can determine
> that object spans two physical pages, because we use a larger
> class->size for this, while the actual object is much smaller
> and fits one physical page, so there is nothing to write to
> the second page and memcpy() size calculation underflows.
> 
> We always know the exact size in bytes of the object
> that we are about to write (store), so use it instead of
> class->size.

I think it's

Fixes: 44f76413496e ("zsmalloc: introduce new object mapping API")