KVM: arm/arm64: Re-check VMA on detecting a poisoned page

When we check for a poisoned page, we use the VMA to tell userspace
about the looming disaster. But we pass a pointer to this VMA
after having released the mmap_sem, which isn't a good idea.

Instead, stash the shift value that goes with this pfn while
we are holding the mmap_sem.

Reported-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Christoffer Dall <christoffer.dall@arm.com>
Link: https://lore.kernel.org/r/20191211165651.7889-3-maz@kernel.org
Link: https://lore.kernel.org/r/20191217123809.197392-1-james.morse@arm.com

diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
index 0b32a90..e3ad950 100644 (file)
--- a/virt/kvm/arm/mmu.c
+++ b/virt/kvm/arm/mmu.c
@@ -1596,16 +1596,8 @@ static void invalidate_icache_guest_page(kvm_pfn_t pfn, unsigned long size)
        __invalidate_icache_guest_page(pfn, size);
 }
 
-static void kvm_send_hwpoison_signal(unsigned long address,
-                                    struct vm_area_struct *vma)
+static void kvm_send_hwpoison_signal(unsigned long address, short lsb)
 {
-       short lsb;
-
-       if (is_vm_hugetlb_page(vma))
-               lsb = huge_page_shift(hstate_vma(vma));
-       else
-               lsb = PAGE_SHIFT;
-
        send_sig_mceerr(BUS_MCEERR_AR, (void __user *)address, lsb, current);
 }
 
@@ -1678,6 +1670,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
        struct kvm *kvm = vcpu->kvm;
        struct kvm_mmu_memory_cache *memcache = &vcpu->arch.mmu_page_cache;
        struct vm_area_struct *vma;
+       short vma_shift;
        kvm_pfn_t pfn;
        pgprot_t mem_type = PAGE_S2;
        bool logging_active = memslot_is_logging(memslot);
@@ -1701,7 +1694,12 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
                return -EFAULT;
        }
 
-       vma_pagesize = vma_kernel_pagesize(vma);
+       if (is_vm_hugetlb_page(vma))
+               vma_shift = huge_page_shift(hstate_vma(vma));
+       else
+               vma_shift = PAGE_SHIFT;
+
+       vma_pagesize = 1ULL << vma_shift;
        if (logging_active ||
            (vma->vm_flags & VM_PFNMAP) ||
            !fault_supports_stage2_huge_mapping(memslot, hva, vma_pagesize)) {
@@ -1741,7 +1739,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 
        pfn = gfn_to_pfn_prot(kvm, gfn, write_fault, &writable);
        if (pfn == KVM_PFN_ERR_HWPOISON) {
-               kvm_send_hwpoison_signal(hva, vma);
+               kvm_send_hwpoison_signal(hva, vma_shift);
                return 0;
        }
        if (is_error_noslot_pfn(pfn))