Messages in this thread | | | Date | Fri, 25 Mar 2022 17:46:37 +0100 | Subject | Re: [RFC PATCH] KVM: x86/mmu: fix general protection fault in kvm_mmu_uninit_tdp_mmu | From | Christophe JAILLET <> |
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Le 25/03/2022 à 17:38, Pavel Skripkin a écrit : > Syzbot reported GPF in kvm_mmu_uninit_tdp_mmu(), which is caused by > passing NULL pointer to flush_workqueue(). > > tdp_mmu_zap_wq is allocated via alloc_workqueue() which may fail. There > is no error hanling and kvm_mmu_uninit_tdp_mmu() return value is simply > ignored. Even all kvm_*_init_vm() functions are void, so the easiest > solution is to check that tdp_mmu_zap_wq is valid pointer before passing > it somewhere. > > Fixes: 22b94c4b63eb ("KVM: x86/mmu: Zap invalidated roots via asynchronous worker") > Reported-and-tested-by: syzbot+717ed82268812a643b28@syzkaller.appspotmail.com > Signed-off-by: Pavel Skripkin <paskripkin@gmail.com> > --- > arch/x86/kvm/mmu/tdp_mmu.c | 14 +++++++++----- > 1 file changed, 9 insertions(+), 5 deletions(-) > > 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);
Hi, unrelated to the patch, but flush_workqueue() is redundant and could be removed. destroy_workqueue() already drains the queue.
Just my 2c, CJ
> + } > > 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)
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