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Date: Fri, 29 Jul 2022 13:46:38 -0500 From: Coleman Dietsch <dietschc@....edu> To: kvm@...r.kernel.org Cc: Coleman Dietsch <dietschc@....edu>, Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, "H . Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org, skhan@...uxfoundation.org, Pavel Skripkin <paskripkin@...il.com>, linux-kernel-mentees@...ts.linuxfoundation.org Subject: [PATCH v2 0/2] KVM: x86/xen: Prevent xen timer init when running This patch series was created to address the following bug found by syzbot WARNING: ODEBUG bug in kvm_xen_vcpu_set_attr. When running the syzbot reproducer code, the following crash dump occurs: ODEBUG: init active (active state 0) object type: hrtimer hint: xen_timer_callbac0 RIP: 0010:debug_print_object+0x16e/0x250 lib/debugobjects.c:502 Call Trace: __debug_object_init debug_hrtimer_init debug_init hrtimer_init kvm_xen_init_timer kvm_xen_vcpu_set_attr kvm_arch_vcpu_ioctl kvm_vcpu_ioctl vfs_ioctl The ODEBUG bug crash appears to be happening when vcpu->arch.xen.timer is already set and kvm_xen_init_timer() is called, which appears to be the result of two separate issues. The first issue is that kvm_xen_init_timer() is run "every" KVM_XEN_VCPU_ATTR_TYPE_TIMER. This is addressed in patch 1. The second issue is that the stop xen timer code should be run before changing the IRQ vector. This is addressed in patch 2 with some cleanup. version 2 changes (mostly feedback from Sean Christopherson) -split patch into 2 patches -fix changelogs to be more descriptive -fix formatting issues -add check for existing xen timer before trying to initialize another one -removed conditional for kvm_xen_stop_timer() so that it always runs -ensure that xen timer is stopped before changing IRQ vector -streamlined switch case KVM_XEN_VCPU_ATTR_TYPE_TIMER a bit Coleman Dietsch (2): KVM: x86/xen: Initialize Xen timer only once KVM: x86/xen: Stop Xen timer before changing the IRQ vector arch/x86/kvm/xen.c | 32 +++++++++++++++++--------------- 1 file changed, 17 insertions(+), 15 deletions(-) -- 2.34.1
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