KVM: async_pf: mm->mm_users can not pin apf->mm (41c22f62) · Commits · 戴 / test

get_user_pages(mm) is simply wrong if mm->mm_users == 0 and exit_mmap/etc was already called (or is in progress), mm->mm_count can only pin mm->pgd and mm_struct itself. Change kvm_setup_async_pf/async_pf_execute to inc/dec mm->mm_users. kvm_create_vm/kvm_destroy_vm play with ->mm_count too but this case looks fine at first glance, it seems that this ->mm is only used to verify that current->mm == kvm->mm. Signed-off-by:

Oleg Nesterov <oleg@redhat.com> Cc: stable@vger.kernel.org Signed-off-by:

Paolo Bonzini <pbonzini@redhat.com>

virt/kvm/async_pf.c

+4 −4

Original line number	Diff line number	Diff line
		@@ -101,7 +101,7 @@ static void async_pf_execute(struct work_struct *work)
		if (waitqueue_active(&vcpu->wq))
		wake_up_interruptible(&vcpu->wq);

		mmdrop(mm);
		mmput(mm);
		kvm_put_kvm(vcpu->kvm);
		}

		@@ -118,7 +118,7 @@ void kvm_clear_async_pf_completion_queue(struct kvm_vcpu *vcpu)
		flush_work(&work->work);
		#else
		if (cancel_work_sync(&work->work)) {
		mmdrop(work->mm);
		mmput(work->mm);
		kvm_put_kvm(vcpu->kvm); /* == work->vcpu->kvm */
		kmem_cache_free(async_pf_cache, work);
		}
		@@ -183,7 +183,7 @@ int kvm_setup_async_pf(struct kvm_vcpu *vcpu, gva_t gva, unsigned long hva,
		work->addr = hva;
		work->arch = *arch;
		work->mm = current->mm;
		atomic_inc(&work->mm->mm_count);
		atomic_inc(&work->mm->mm_users);
		kvm_get_kvm(work->vcpu->kvm);

		/* this can't really happen otherwise gfn_to_pfn_async
		@@ -201,7 +201,7 @@ int kvm_setup_async_pf(struct kvm_vcpu *vcpu, gva_t gva, unsigned long hva,
		return 1;
		retry_sync:
		kvm_put_kvm(work->vcpu->kvm);
		mmdrop(work->mm);
		mmput(work->mm);
		kmem_cache_free(async_pf_cache, work);
		return 0;
		}

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