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
