Re: [PATCH V3] mm: prevent page_frag_alloc() from corrupting the memory

[Maurizio Lombardi]

út 9. 8. 2022 v 2:14 odesílatel Andrew Morton
<akpm@xxxxxxxxxxxxxxxxxxxx> napsal:
>
> On Fri, 15 Jul 2022 14:50:13 +0200 Maurizio Lombardi <mlombard@xxxxxxxxxx> wrote:
>
> > A number of drivers call page_frag_alloc() with a
> > fragment's size > PAGE_SIZE.
> > In low memory conditions, __page_frag_cache_refill() may fail the order 3
> > cache allocation and fall back to order 0;
> > In this case, the cache will be smaller than the fragment, causing
> > memory corruptions.
> >
> > Prevent this from happening by checking if the newly allocated cache
> > is large enough for the fragment; if not, the allocation will fail
> > and page_frag_alloc() will return NULL.
>
> Can we come up with a Fixes: for this?

I think the bug has been introduced in kernel 3.19-rc1
Fixes: ffde7328a36d16e626bae8468571858d71cd010b

>
> Should this fix be backported into -stable kernels?

Yes, IMO this should be backported to -stable

Thanks,
Maurizio