Commit 005ba37c authored by Sean Christopherson's avatar Sean Christopherson Committed by Paolo Bonzini
Browse files

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: 936a5fe6 ("thp: kvm mmu transparent hugepage support")
Reported-by: default avatar <syzbot+c9d1fb51ac9d0d10c39d@syzkaller.appspotmail.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: default avatarSean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 22b1d57b

arch/x86/kvm/mmu/mmu.c

+2 −2
Original line number Diff line number Diff line
@@ -3344,7 +3344,7 @@ static void transparent_hugepage_adjust(struct kvm_vcpu *vcpu, 
	 */

	if (!is_error_noslot_pfn(pfn) && !kvm_is_reserved_pfn(pfn) &&

	    !kvm_is_zone_device_pfn(pfn) && level == PT_PAGE_TABLE_LEVEL &&

	    PageTransCompoundMap(pfn_to_page(pfn))) {

	    kvm_is_transparent_hugepage(pfn)) {

		unsigned long mask;



		/*
@@ -5961,7 +5961,7 @@ restart: 
		 */

		if (sp->role.direct && !kvm_is_reserved_pfn(pfn) &&

		    !kvm_is_zone_device_pfn(pfn) &&

		    PageTransCompoundMap(pfn_to_page(pfn))) {

		    kvm_is_transparent_hugepage(pfn)) {

			pte_list_remove(rmap_head, sptep);



			if (kvm_available_flush_tlb_with_range())

include/linux/huge_mm.h

+6 −0
Original line number Diff line number Diff line
@@ -160,6 +160,7 @@ extern unsigned long thp_get_unmapped_area(struct file *filp, 


extern void prep_transhuge_page(struct page *page);

extern void free_transhuge_page(struct page *page);

bool is_transparent_hugepage(struct page *page);



bool can_split_huge_page(struct page *page, int *pextra_pins);

int split_huge_page_to_list(struct page *page, struct list_head *list);
@@ -308,6 +309,11 @@ static inline bool transhuge_vma_suitable(struct vm_area_struct *vma, 


static inline void prep_transhuge_page(struct page *page) {}



static inline bool is_transparent_hugepage(struct page *page)

{

	return false;

}



#define transparent_hugepage_flags 0UL



#define thp_get_unmapped_area	NULL

include/linux/kvm_host.h

+1 −0
Original line number Diff line number Diff line
@@ -976,6 +976,7 @@ int kvm_cpu_has_pending_timer(struct kvm_vcpu *vcpu); 


bool kvm_is_reserved_pfn(kvm_pfn_t pfn);

bool kvm_is_zone_device_pfn(kvm_pfn_t pfn);

bool kvm_is_transparent_hugepage(kvm_pfn_t pfn);



struct kvm_irq_ack_notifier {

	struct hlist_node link;

mm/huge_memory.c

+11 −0
Original line number Diff line number Diff line
@@ -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)

{

virt/kvm/arm/mmu.c

+1 −7
Original line number Diff line number Diff line
@@ -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

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