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mm: thp: KVM: Explicitly check for THP when populating secondary MMU

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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: 936a5fe6e6 ("thp: kvm mmu transparent hugepage support")
Reported-by: syzbot+c9d1fb51ac9d0d10c39d@syzkaller.appspotmail.com
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson
2020-01-08 12:24:36 -08:00
committed by Paolo Bonzini
parent 22b1d57b03
commit 005ba37cb8
6 changed files with 31 additions and 9 deletions
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8
virt/kvm/arm/mmu.c
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@@ -1377,14 +1377,8 @@ static bool transparent_hugepage_adjust(kvm_pfn_t *pfnp, phys_addr_t *ipap)
{
kvm_pfn_t pfn = *pfnp;
gfn_t gfn = *ipap >> PAGE_SHIFT;
struct page *page = pfn_to_page(pfn);
/*
* PageTransCompoundMap() returns true for THP and
* hugetlbfs. Make sure the adjustment is done only for THP
* pages.
*/
if (!PageHuge(page) && PageTransCompoundMap(page)) {
if (kvm_is_transparent_hugepage(pfn)) {
unsigned long mask;
/*
* The address we faulted on is backed by a transparent huge