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Subject[PATCH 0/2] Fix prep_compound_gigantic_page ref count adjustment
Date
These patches address the possible race between prep_compound_gigantic_page
and __page_cache_add_speculative as described by Jann Horn in [1].

The first patch simply removes the unnecessary/obsolete helper routine
prep_compound_huge_page to make the actual fix a little simpler.

The second patch is the actual fix and has a detailed explanation in the
commit message.

This potential issue has existed for almost 10 years and I am unaware of
anyone actually hitting the race. I did not cc stable, but would be
happy to squash the patches and send to stable if anyone thinks that is
a good idea.

I could not think of a reliable way to recreate the issue for testing.
Rather, I 'simulated errors' to exercise all the error paths.

Mike Kravetz (2):
hugetlb: remove prep_compound_huge_page cleanup
hugetlb: address ref count racing in prep_compound_gigantic_page

mm/hugetlb.c | 99 ++++++++++++++++++++++++++++++++++++-------------
mm/page_alloc.c | 1 -
2 files changed, 73 insertions(+), 27 deletions(-)

--
2.31.1

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