KVM: PPC: Book3S: Fix race and leak in kvm_vm_ioctl_create_spapr_tce() (47c5310a) · Commits · 戴 / test

Nixiaoming pointed out that there is a memory leak in kvm_vm_ioctl_create_spapr_tce() if the call to anon_inode_getfd() fails; the memory allocated for the kvmppc_spapr_tce_table struct is not freed, and nor are the pages allocated for the iommu tables. In addition, we have already incremented the process's count of locked memory pages, and this doesn't get restored on error. David Hildenbrand pointed out that there is a race in that the function checks early on that there is not already an entry in the stt->iommu_tables list with the same LIOBN, but an entry with the same LIOBN could get added between then and when the new entry is added to the list. This fixes all three problems. To simplify things, we now call anon_inode_getfd() before placing the new entry in the list. The check for an existing entry is done while holding the kvm->lock mutex, immediately before adding the new entry to the list. Finally, on failure we now call kvmppc_account_memlimit to decrement the process's count of locked memory pages. Reported-by:

Nixiaoming <nixiaoming@huawei.com> Reported-by:

David Hildenbrand <david@redhat.com> Signed-off-by:

Paul Mackerras <paulus@ozlabs.org> Signed-off-by:

Paolo Bonzini <pbonzini@redhat.com>

arch/powerpc/kvm/book3s_64_vio.c

+34 −22

Original line number	Diff line number	Diff line
		@@ -294,32 +294,26 @@ long kvm_vm_ioctl_create_spapr_tce(struct kvm *kvm,
		struct kvm_create_spapr_tce_64 *args)
		{
		struct kvmppc_spapr_tce_table *stt = NULL;
		struct kvmppc_spapr_tce_table *siter;
		unsigned long npages, size;
		int ret = -ENOMEM;
		int i;
		int fd = -1;

		if (!args->size)
		return -EINVAL;

		/* Check this LIOBN hasn't been previously allocated */
		list_for_each_entry(stt, &kvm->arch.spapr_tce_tables, list) {
		if (stt->liobn == args->liobn)
		return -EBUSY;
		}

		size = _ALIGN_UP(args->size, PAGE_SIZE >> 3);
		npages = kvmppc_tce_pages(size);
		ret = kvmppc_account_memlimit(kvmppc_stt_pages(npages), true);
		if (ret) {
		stt = NULL;
		goto fail;
		}
		if (ret)
		return ret;

		ret = -ENOMEM;
		stt = kzalloc(sizeof(stt) + npages sizeof(struct page *),
		GFP_KERNEL);
		if (!stt)
		goto fail;
		goto fail_acct;

		stt->liobn = args->liobn;
		stt->page_shift = args->page_shift;
		@@ -334,24 +328,42 @@ long kvm_vm_ioctl_create_spapr_tce(struct kvm *kvm,
		goto fail;
		}

		kvm_get_kvm(kvm);
		ret = fd = anon_inode_getfd("kvm-spapr-tce", &kvm_spapr_tce_fops,
		stt, O_RDWR \| O_CLOEXEC);
		if (ret < 0)
		goto fail;

		mutex_lock(&kvm->lock);

		/* Check this LIOBN hasn't been previously allocated */
		ret = 0;
		list_for_each_entry(siter, &kvm->arch.spapr_tce_tables, list) {
		if (siter->liobn == args->liobn) {
		ret = -EBUSY;
		break;
		}
		}

		if (!ret) {
		list_add_rcu(&stt->list, &kvm->arch.spapr_tce_tables);
		kvm_get_kvm(kvm);
		}

		mutex_unlock(&kvm->lock);

		return anon_inode_getfd("kvm-spapr-tce", &kvm_spapr_tce_fops,
		stt, O_RDWR \| O_CLOEXEC);
		if (!ret)
		return fd;

		put_unused_fd(fd);

		fail:
		if (stt) {
		for (i = 0; i < npages; i++)
		if (stt->pages[i])
		__free_page(stt->pages[i]);

		kfree(stt);
		}
		fail_acct:
		kvmppc_account_memlimit(kvmppc_stt_pages(npages), false);
		return ret;
		}

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