From: Andrew Morton <akpm@linux-foundation.org>
To: Mike Kravetz <mike.kravetz@oracle.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Zi Yan <ziy@nvidia.com>, Davidlohr Bueso <dbueso@suse.de>,
"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Matthew Wilcox <willy@infradead.org>,
Oscar Salvador <osalvador@suse.de>,
Joao Martins <joao.m.martins@oracle.com>,
stable@vger.kernel.org
Subject: Re: [PATCH 1/2] hugetlb: fix update_and_free_page contig page struct assumption
Date: Wed, 17 Feb 2021 11:02:52 -0800 [thread overview]
Message-ID: <20210217110252.185c7f5cd5a87c3f7b0c0144@linux-foundation.org> (raw)
In-Reply-To: <20210217184926.33567-1-mike.kravetz@oracle.com>
On Wed, 17 Feb 2021 10:49:25 -0800 Mike Kravetz <mike.kravetz@oracle.com> wrote:
> page structs are not guaranteed to be contiguous for gigantic pages. The
> routine update_and_free_page can encounter a gigantic page, yet it assumes
> page structs are contiguous when setting page flags in subpages.
>
> If update_and_free_page encounters non-contiguous page structs, we can
> see “BUG: Bad page state in process …” errors.
>
> Non-contiguous page structs are generally not an issue. However, they can
> exist with a specific kernel configuration and hotplug operations. For
> example: Configure the kernel with CONFIG_SPARSEMEM and
> !CONFIG_SPARSEMEM_VMEMMAP. Then, hotplug add memory for the area where the
> gigantic page will be allocated.
> Zi Yan outlined steps to reproduce here [1].
>
> [1] https://lore.kernel.org/linux-mm/16F7C58B-4D79-41C5-9B64-A1A1628F4AF2@nvidia.com/
>
> Fixes: 944d9fec8d7a ("hugetlb: add support for gigantic page allocation at runtime")
June 2014. That's a long lurk time for a bug. I wonder if some later
commit revealed it.
I guess it doesn't matter a lot, but some -stable kernel maintainers
might wonder if they really need this fix...
next prev parent reply other threads:[~2021-02-17 19:04 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-17 18:49 [PATCH 1/2] hugetlb: fix update_and_free_page contig page struct assumption Mike Kravetz
2021-02-17 18:49 ` [PATCH 2/2] hugetlb: fix copy_huge_page_from_user " Mike Kravetz
2021-02-17 19:02 ` Andrew Morton [this message]
2021-02-17 19:38 ` [PATCH 1/2] hugetlb: fix update_and_free_page " Mike Kravetz
2021-02-18 14:45 ` Matthew Wilcox
2021-02-18 17:25 ` Jason Gunthorpe
2021-02-18 17:27 ` Zi Yan
2021-02-18 17:32 ` Jason Gunthorpe
2021-02-18 17:40 ` Zi Yan
2021-02-18 17:51 ` Mike Kravetz
2021-02-18 18:50 ` Zi Yan
2021-02-18 17:34 ` Mike Kravetz
2021-02-18 21:43 ` Mike Kravetz
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