linux-kernel - Re: [PATCH 5.15] mm: validate buddy page before using

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Date:   Mon, 20 Jun 2022 12:17:56 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Xianting Tian <xianting.tian@...ux.alibaba.com>
Cc:     akpm@...ux-foundation.org, ziy@...dia.com, stable@...r.kernel.org,
        guoren@...nel.org, huanyi.xj@...baba-inc.com, guohanjun@...wei.com,
        zjb194813@...baba-inc.com, tianhu.hh@...baba-inc.com,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5.15] mm: validate buddy page before using

On Fri, Jun 17, 2022 at 12:17:45AM +0800, Xianting Tian wrote:
> Commit 787af64d05cd ("mm: page_alloc: validate buddy before check its migratetype.")
> fixes a bug in 1dd214b8f21c and there is a similar bug in d9dddbf55667 that
> can be fixed in a similar way too.
> 
> In unset_migratetype_isolate(), we also need the fix, so move page_is_buddy()
> from mm/page_alloc.c to mm/internal.h
> 
> In addition, for RISC-V arch the first 2MB RAM could be reserved for opensbi,
> so it would have pfn_base=512 and mem_map began with 512th PFN when
> CONFIG_FLATMEM=y.
> But __find_buddy_pfn algorithm thinks the start pfn 0, it could get 0 pfn or
> less than the pfn_base value. We need page_is_buddy() to verify the buddy to
> prevent accessing an invalid buddy.
> 
> Fixes: d9dddbf55667 ("mm/page_alloc: prevent merging between isolated and other pageblocks")
> Cc: stable@...r.kernel.org
> Reported-by: zjb194813@...baba-inc.com
> Reported-by: tianhu.hh@...baba-inc.com
> Signed-off-by: Xianting Tian <xianting.tian@...ux.alibaba.com>
> ---
>  mm/internal.h       | 34 ++++++++++++++++++++++++++++++++++
>  mm/page_alloc.c     | 37 +++----------------------------------
>  mm/page_isolation.c |  3 ++-
>  3 files changed, 39 insertions(+), 35 deletions(-)

What is the commit id of this in Linus's tree?

thanks,

greg k-h