From bbaf0e2b1c1b4f88abd6ef49576f0efb1734eae5 Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Wed, 26 Apr 2017 16:56:26 +0200 Subject: kvm: async_pf: fix rcu_irq_enter() with irqs enabled MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit native_safe_halt enables interrupts, and you just shouldn't call rcu_irq_enter() with interrupts enabled. Reorder the call with the following local_irq_disable() to respect the invariant. Reported-by: Ross Zwisler Cc: stable@vger.kernel.org Signed-off-by: Paolo Bonzini Acked-by: Paul E. McKenney Tested-by: Wanpeng Li Signed-off-by: Radim Krčmář --- arch/x86/kernel/kvm.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'arch/x86') diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c index da5c09789984..43e10d6fdbed 100644 --- a/arch/x86/kernel/kvm.c +++ b/arch/x86/kernel/kvm.c @@ -161,8 +161,8 @@ void kvm_async_pf_task_wait(u32 token) */ rcu_irq_exit(); native_safe_halt(); - rcu_irq_enter(); local_irq_disable(); + rcu_irq_enter(); } } if (!n.halted) -- cgit From d4912215d1031e4fb3d1038d2e1857218dba0d0a Mon Sep 17 00:00:00 2001 From: Wanpeng Li Date: Mon, 5 Jun 2017 05:19:09 -0700 Subject: KVM: nVMX: Fix exception injection MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit WARNING: CPU: 3 PID: 2840 at arch/x86/kvm/vmx.c:10966 nested_vmx_vmexit+0xdcd/0xde0 [kvm_intel] CPU: 3 PID: 2840 Comm: qemu-system-x86 Tainted: G OE 4.12.0-rc3+ #23 RIP: 0010:nested_vmx_vmexit+0xdcd/0xde0 [kvm_intel] Call Trace: ? kvm_check_async_pf_completion+0xef/0x120 [kvm] ? rcu_read_lock_sched_held+0x79/0x80 vmx_queue_exception+0x104/0x160 [kvm_intel] ? vmx_queue_exception+0x104/0x160 [kvm_intel] kvm_arch_vcpu_ioctl_run+0x1171/0x1ce0 [kvm] ? kvm_arch_vcpu_load+0x47/0x240 [kvm] ? kvm_arch_vcpu_load+0x62/0x240 [kvm] kvm_vcpu_ioctl+0x384/0x7b0 [kvm] ? kvm_vcpu_ioctl+0x384/0x7b0 [kvm] ? __fget+0xf3/0x210 do_vfs_ioctl+0xa4/0x700 ? __fget+0x114/0x210 SyS_ioctl+0x79/0x90 do_syscall_64+0x81/0x220 entry_SYSCALL64_slow_path+0x25/0x25 This is triggered occasionally by running both win7 and win2016 in L2, in addition, EPT is disabled on both L1 and L2. It can't be reproduced easily. Commit 0b6ac343fc (KVM: nVMX: Correct handling of exception injection) mentioned that "KVM wants to inject page-faults which it got to the guest. This function assumes it is called with the exit reason in vmcs02 being a #PF exception". Commit e011c663 (KVM: nVMX: Check all exceptions for intercept during delivery to L2) allows to check all exceptions for intercept during delivery to L2. However, there is no guarantee the exit reason is exception currently, when there is an external interrupt occurred on host, maybe a time interrupt for host which should not be injected to guest, and somewhere queues an exception, then the function nested_vmx_check_exception() will be called and the vmexit emulation codes will try to emulate the "Acknowledge interrupt on exit" behavior, the warning is triggered. Reusing the exit reason from the L2->L0 vmexit is wrong in this case, the reason must always be EXCEPTION_NMI when injecting an exception into L1 as a nested vmexit. Cc: Paolo Bonzini Cc: Radim Krčmář Signed-off-by: Wanpeng Li Fixes: e011c663b9c7 ("KVM: nVMX: Check all exceptions for intercept during delivery to L2") Signed-off-by: Radim Krčmář --- arch/x86/kvm/vmx.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'arch/x86') diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 9b4b5d6dcd34..ca5d2b93385c 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -2425,7 +2425,7 @@ static int nested_vmx_check_exception(struct kvm_vcpu *vcpu, unsigned nr) if (!(vmcs12->exception_bitmap & (1u << nr))) return 0; - nested_vmx_vmexit(vcpu, to_vmx(vcpu)->exit_reason, + nested_vmx_vmexit(vcpu, EXIT_REASON_EXCEPTION_NMI, vmcs_read32(VM_EXIT_INTR_INFO), vmcs_readl(EXIT_QUALIFICATION)); return 1; -- cgit From a3641631d14571242eec0d30c9faa786cbf52d44 Mon Sep 17 00:00:00 2001 From: Wanpeng Li Date: Thu, 8 Jun 2017 01:22:07 -0700 Subject: KVM: cpuid: Fix read/write out-of-bounds vulnerability in cpuid emulation MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit If "i" is the last element in the vcpu->arch.cpuid_entries[] array, it potentially can be exploited the vulnerability. this will out-of-bounds read and write. Luckily, the effect is small: /* when no next entry is found, the current entry[i] is reselected */ for (j = i + 1; ; j = (j + 1) % nent) { struct kvm_cpuid_entry2 *ej = &vcpu->arch.cpuid_entries[j]; if (ej->function == e->function) { It reads ej->maxphyaddr, which is user controlled. However... ej->flags |= KVM_CPUID_FLAG_STATE_READ_NEXT; After cpuid_entries there is int maxphyaddr; struct x86_emulate_ctxt emulate_ctxt; /* 16-byte aligned */ So we have: - cpuid_entries at offset 1B50 (6992) - maxphyaddr at offset 27D0 (6992 + 3200 = 10192) - padding at 27D4...27DF - emulate_ctxt at 27E0 And it writes in the padding. Pfew, writing the ops field of emulate_ctxt would have been much worse. This patch fixes it by modding the index to avoid the out-of-bounds access. Worst case, i == j and ej->function == e->function, the loop can bail out. Reported-by: Moguofang Cc: Paolo Bonzini Cc: Radim Krčmář Cc: Guofang Mo Cc: stable@vger.kernel.org Signed-off-by: Wanpeng Li Signed-off-by: Paolo Bonzini --- arch/x86/kvm/cpuid.c | 20 +++++++++++--------- 1 file changed, 11 insertions(+), 9 deletions(-) (limited to 'arch/x86') diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index a181ae76c71c..59ca2eea522c 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -780,18 +780,20 @@ out: static int move_to_next_stateful_cpuid_entry(struct kvm_vcpu *vcpu, int i) { struct kvm_cpuid_entry2 *e = &vcpu->arch.cpuid_entries[i]; - int j, nent = vcpu->arch.cpuid_nent; + struct kvm_cpuid_entry2 *ej; + int j = i; + int nent = vcpu->arch.cpuid_nent; e->flags &= ~KVM_CPUID_FLAG_STATE_READ_NEXT; /* when no next entry is found, the current entry[i] is reselected */ - for (j = i + 1; ; j = (j + 1) % nent) { - struct kvm_cpuid_entry2 *ej = &vcpu->arch.cpuid_entries[j]; - if (ej->function == e->function) { - ej->flags |= KVM_CPUID_FLAG_STATE_READ_NEXT; - return j; - } - } - return 0; /* silence gcc, even though control never reaches here */ + do { + j = (j + 1) % nent; + ej = &vcpu->arch.cpuid_entries[j]; + } while (ej->function != e->function); + + ej->flags |= KVM_CPUID_FLAG_STATE_READ_NEXT; + + return j; } /* find an entry with matching function, matching index (if needed), and that -- cgit From 9bc1f09f6fa76fdf31eb7d6a4a4df43574725f93 Mon Sep 17 00:00:00 2001 From: Wanpeng Li Date: Thu, 8 Jun 2017 20:13:40 -0700 Subject: KVM: async_pf: avoid async pf injection when in guest mode MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit INFO: task gnome-terminal-:1734 blocked for more than 120 seconds. Not tainted 4.12.0-rc4+ #8 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. gnome-terminal- D 0 1734 1015 0x00000000 Call Trace: __schedule+0x3cd/0xb30 schedule+0x40/0x90 kvm_async_pf_task_wait+0x1cc/0x270 ? __vfs_read+0x37/0x150 ? prepare_to_swait+0x22/0x70 do_async_page_fault+0x77/0xb0 ? do_async_page_fault+0x77/0xb0 async_page_fault+0x28/0x30 This is triggered by running both win7 and win2016 on L1 KVM simultaneously, and then gives stress to memory on L1, I can observed this hang on L1 when at least ~70% swap area is occupied on L0. This is due to async pf was injected to L2 which should be injected to L1, L2 guest starts receiving pagefault w/ bogus %cr2(apf token from the host actually), and L1 guest starts accumulating tasks stuck in D state in kvm_async_pf_task_wait() since missing PAGE_READY async_pfs. This patch fixes the hang by doing async pf when executing L1 guest. Cc: Paolo Bonzini Cc: Radim Krčmář Cc: stable@vger.kernel.org Signed-off-by: Wanpeng Li Signed-off-by: Paolo Bonzini --- arch/x86/kvm/mmu.c | 7 +++++-- arch/x86/kvm/mmu.h | 1 + arch/x86/kvm/x86.c | 3 +-- 3 files changed, 7 insertions(+), 4 deletions(-) (limited to 'arch/x86') diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index 5d3376f67794..cb8225969255 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -3698,12 +3698,15 @@ static int kvm_arch_setup_async_pf(struct kvm_vcpu *vcpu, gva_t gva, gfn_t gfn) return kvm_setup_async_pf(vcpu, gva, kvm_vcpu_gfn_to_hva(vcpu, gfn), &arch); } -static bool can_do_async_pf(struct kvm_vcpu *vcpu) +bool kvm_can_do_async_pf(struct kvm_vcpu *vcpu) { if (unlikely(!lapic_in_kernel(vcpu) || kvm_event_needs_reinjection(vcpu))) return false; + if (is_guest_mode(vcpu)) + return false; + return kvm_x86_ops->interrupt_allowed(vcpu); } @@ -3719,7 +3722,7 @@ static bool try_async_pf(struct kvm_vcpu *vcpu, bool prefault, gfn_t gfn, if (!async) return false; /* *pfn has correct page already */ - if (!prefault && can_do_async_pf(vcpu)) { + if (!prefault && kvm_can_do_async_pf(vcpu)) { trace_kvm_try_async_get_page(gva, gfn); if (kvm_find_async_pf_gfn(vcpu, gfn)) { trace_kvm_async_pf_doublefault(gva, gfn); diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h index 27975807cc64..330bf3a811fb 100644 --- a/arch/x86/kvm/mmu.h +++ b/arch/x86/kvm/mmu.h @@ -76,6 +76,7 @@ int handle_mmio_page_fault(struct kvm_vcpu *vcpu, u64 addr, bool direct); void kvm_init_shadow_mmu(struct kvm_vcpu *vcpu); void kvm_init_shadow_ept_mmu(struct kvm_vcpu *vcpu, bool execonly, bool accessed_dirty); +bool kvm_can_do_async_pf(struct kvm_vcpu *vcpu); static inline unsigned int kvm_mmu_available_pages(struct kvm *kvm) { diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index a2cd0997343c..87d3cb901935 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -8607,8 +8607,7 @@ bool kvm_arch_can_inject_async_page_present(struct kvm_vcpu *vcpu) if (!(vcpu->arch.apf.msr_val & KVM_ASYNC_PF_ENABLED)) return true; else - return !kvm_event_needs_reinjection(vcpu) && - kvm_x86_ops->interrupt_allowed(vcpu); + return kvm_can_do_async_pf(vcpu); } void kvm_arch_start_assignment(struct kvm *kvm) -- cgit