Re: [PATCH 2/3] zram: do not use copy_page with non-page alinged address

Minchan Kim
2017-04-14T15:40:38Z

On Fri, Apr 14, 2017 at 02:41:05PM +0900, Sergey Senozhatsky wrote:
> Hello,
>
> On (04/13/17 09:17), Minchan Kim wrote:
> > The copy_page is optimized memcpy for page-alinged address.
> > If it is used with non-page aligned address, it can corrupt memory which
> > means system corruption. With zram, it can happen with
> >
> > 1. 64K architecture
> > 2. partial IO
> > 3. slub debug
> >
> > Partial IO need to allocate a page and zram allocates it via kmalloc.
> > With slub debug, kmalloc(PAGE_SIZE) doesn't return page-size aligned
> > address. And finally, copy_page(mem, cmem) corrupts memory.
>
> which would be the case for many other copy_page() calls in the kernel.
> right? if so - should the fix be in copy_page() then?

I thought about it but was not sure it's good idea by several reasons
(but don't want to discuss it in this thread).

Anyway, it's stable stuff so I don't want to make the patch bloat.
If you believe it is right direction and valuable, you could be
a volunteer. :)

Thanks.