linux-kernel - Re: [PATCH] mm/z3fold: Fix z3fold_buddy

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Tue, 2 Jul 2019 09:56:34 -0700
From:   Henry Burns <henryburns@...gle.com>
To:     Vitaly Wool <vitalywool@...il.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Vitaly Vul <vitaly.vul@...y.com>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        Xidong Wang <wangxidong_97@....com>,
        Shakeel Butt <shakeelb@...gle.com>,
        Jonathan Adams <jwadams@...gle.com>,
        Linux-MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm/z3fold: Fix z3fold_buddy_slots use after free

On Tue, Jul 2, 2019 at 12:45 AM Vitaly Wool <vitalywool@...il.com> wrote:
>
> Hi Henry,
>
> On Mon, Jul 1, 2019 at 8:31 PM Henry Burns <henryburns@...gle.com> wrote:
> >
> > Running z3fold stress testing with address sanitization
> > showed zhdr->slots was being used after it was freed.
> >
> > z3fold_free(z3fold_pool, handle)
> >   free_handle(handle)
> >     kmem_cache_free(pool->c_handle, zhdr->slots)
> >   release_z3fold_page_locked_list(kref)
> >     __release_z3fold_page(zhdr, true)
> >       zhdr_to_pool(zhdr)
> >         slots_to_pool(zhdr->slots)  *BOOM*
>
> Thanks for looking into this. I'm not entirely sure I'm all for
> splitting free_handle() but let me think about it.
>
> > Instead we split free_handle into two functions, release_handle()
> > and free_slots(). We use release_handle() in place of free_handle(),
> > and use free_slots() to call kmem_cache_free() after
> > __release_z3fold_page() is done.
>
> A little less intrusive solution would be to move backlink to pool
> from slots back to z3fold_header. Looks like it was a bad idea from
> the start.
>
> Best regards,
>    Vitaly

We still want z3fold pages to be movable though. Wouldn't moving
the backink to the pool from slots to z3fold_header prevent us from
enabling migration?