On 3/25/22 16:10, syzbot wrote:
Hello, syzbot found the following issue on: HEAD commit: f9006d9269ea Add linux-next specific files for 20220321 git tree: linux-next console output: https://syzkaller.appspot.com/x/log.txt?x=101191bd700000 kernel config: https://syzkaller.appspot.com/x/.config?x=c1619ffa2b0259a1 dashboard link: https://syzkaller.appspot.com/bug?extid=717ed82268812a643b28 compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=109e8f5d700000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1666180b700000 IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+717ed82268812a643b28@xxxxxxxxxxxxxxxxxxxxxxxxx
The following code is not safe: arch/x86/kvm/mmu/tdp_mmu.c: 28 kvm->arch.tdp_mmu_zap_wq = 29 alloc_workqueue("kvm", WQ_UNBOUND|WQ_MEM_RECLAIM|WQ_CPU_INTENSIVE, 0); 30 31 return true;Looks like kvm_mmu_init_tdp_mmu() error value is just ignored, and then all kvm_*_init_vm() functions are void, so the easiest solution is to check that tdp_mmu_zap_wq is valid pointer
#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
With regards, Pavel Skripkin
diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c index e7e7876251b3..b3e8ff7ac5b0 100644 --- a/arch/x86/kvm/mmu/tdp_mmu.c +++ b/arch/x86/kvm/mmu/tdp_mmu.c @@ -48,8 +48,10 @@ void kvm_mmu_uninit_tdp_mmu(struct kvm *kvm) if (!kvm->arch.tdp_mmu_enabled) return; - flush_workqueue(kvm->arch.tdp_mmu_zap_wq); - destroy_workqueue(kvm->arch.tdp_mmu_zap_wq); + if (kvm->arch.tdp_mmu_zap_wq) { + flush_workqueue(kvm->arch.tdp_mmu_zap_wq); + destroy_workqueue(kvm->arch.tdp_mmu_zap_wq); + } WARN_ON(!list_empty(&kvm->arch.tdp_mmu_pages)); WARN_ON(!list_empty(&kvm->arch.tdp_mmu_roots)); @@ -119,9 +121,11 @@ static void tdp_mmu_zap_root_work(struct work_struct *work) static void tdp_mmu_schedule_zap_root(struct kvm *kvm, struct kvm_mmu_page *root) { - root->tdp_mmu_async_data = kvm; - INIT_WORK(&root->tdp_mmu_async_work, tdp_mmu_zap_root_work); - queue_work(kvm->arch.tdp_mmu_zap_wq, &root->tdp_mmu_async_work); + if (kvm->arch.tdp_mmu_zap_wq) { + root->tdp_mmu_async_data = kvm; + INIT_WORK(&root->tdp_mmu_async_work, tdp_mmu_zap_root_work); + queue_work(kvm->arch.tdp_mmu_zap_wq, &root->tdp_mmu_async_work); + } } static inline bool kvm_tdp_root_mark_invalid(struct kvm_mmu_page *page)