From 005ba37cb89bcc0cf63c2029a41f8db165aeb615 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Wed, 8 Jan 2020 12:24:36 -0800 Subject: mm: thp: KVM: Explicitly check for THP when populating secondary MMU Add a helper, is_transparent_hugepage(), to explicitly check whether a compound page is a THP and use it when populating KVM's secondary MMU. The explicit check fixes a bug where a remapped compound page, e.g. for an XDP Rx socket, is mapped into a KVM guest and is mistaken for a THP, which results in KVM incorrectly creating a huge page in its secondary MMU. Fixes: 936a5fe6e6148 ("thp: kvm mmu transparent hugepage support") Reported-by: syzbot+c9d1fb51ac9d0d10c39d@syzkaller.appspotmail.com Cc: Andrea Arcangeli Cc: stable@vger.kernel.org Signed-off-by: Sean Christopherson Signed-off-by: Paolo Bonzini --- mm/huge_memory.c | 11 +++++++++++ 1 file changed, 11 insertions(+) (limited to 'mm/huge_memory.c') diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 41a0fbddc96b..9b3ee79d0edf 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -527,6 +527,17 @@ void prep_transhuge_page(struct page *page) set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR); } +bool is_transparent_hugepage(struct page *page) +{ + if (!PageCompound(page)) + return 0; + + page = compound_head(page); + return is_huge_zero_page(page) || + page[1].compound_dtor == TRANSHUGE_PAGE_DTOR; +} +EXPORT_SYMBOL_GPL(is_transparent_hugepage); + static unsigned long __thp_get_unmapped_area(struct file *filp, unsigned long len, loff_t off, unsigned long flags, unsigned long size) { -- cgit v1.2.3-59-g8ed1b