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

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Date:   Tue, 9 Aug 2022 13:45:19 +0200
From:   Maurizio Lombardi <mlombard@...hat.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Alexander Duyck <alexander.duyck@...il.com>,
        Jakub Kicinski <kuba@...nel.org>,
        linux-mm <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Netdev <netdev@...r.kernel.org>,
        愚树 <chen45464546@....com>
Subject: Re: [PATCH V3] mm: prevent page_frag_alloc() from corrupting the memory

út 9. 8. 2022 v 2:14 odesílatel Andrew Morton
<akpm@...ux-foundation.org> napsal:
>
> On Fri, 15 Jul 2022 14:50:13 +0200 Maurizio Lombardi <mlombard@...hat.com> 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