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    SubjectRe: [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@vger.kernel.org
    > Reported-by: zjb194813@alibaba-inc.com
    > Reported-by: tianhu.hh@alibaba-inc.com
    > Signed-off-by: Xianting Tian <xianting.tian@linux.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

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