Ping ?
On 2020/12/29 15:11, Like Xu wrote:
Since we know vPMU will not work properly when the guest bit_width(s) of
the [gp|fixed] counters are greater than the host ones, so we can setup a
smaller left shift value and refresh the guest pmu cpuid entry, thus fixing
the following UBSAN shift-out-of-bounds warning:
shift exponent 197 is too large for 64-bit type 'long long unsigned int'
Call Trace:
__dump_stack lib/dump_stack.c:79 [inline]
dump_stack+0x107/0x163 lib/dump_stack.c:120
ubsan_epilogue+0xb/0x5a lib/ubsan.c:148
__ubsan_handle_shift_out_of_bounds.cold+0xb1/0x181 lib/ubsan.c:395
intel_pmu_refresh.cold+0x75/0x99 arch/x86/kvm/vmx/pmu_intel.c:348
kvm_vcpu_after_set_cpuid+0x65a/0xf80 arch/x86/kvm/cpuid.c:177
kvm_vcpu_ioctl_set_cpuid2+0x160/0x440 arch/x86/kvm/cpuid.c:308
kvm_arch_vcpu_ioctl+0x11b6/0x2d70 arch/x86/kvm/x86.c:4709
kvm_vcpu_ioctl+0x7b9/0xdb0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3386
vfs_ioctl fs/ioctl.c:48 [inline]
__do_sys_ioctl fs/ioctl.c:753 [inline]
__se_sys_ioctl fs/ioctl.c:739 [inline]
__x64_sys_ioctl+0x193/0x200 fs/ioctl.c:739
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9
Reported-by: syzbot+ae488dc136a4cc6ba32b@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Like Xu <like.xu@xxxxxxxxxxxxxxx>
---
arch/x86/kvm/vmx/pmu_intel.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index a886a47daebd..a86a1690e75c 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -345,6 +345,7 @@ static void intel_pmu_refresh(struct kvm_vcpu *vcpu)
pmu->nr_arch_gp_counters = min_t(int, eax.split.num_counters,
x86_pmu.num_counters_gp);
+ eax.split.bit_width = min_t(int, eax.split.bit_width, x86_pmu.bit_width_gp);
pmu->counter_bitmask[KVM_PMC_GP] = ((u64)1 << eax.split.bit_width) - 1;
pmu->available_event_types = ~entry->ebx &
((1ull << eax.split.mask_length) - 1);
@@ -355,6 +356,8 @@ static void intel_pmu_refresh(struct kvm_vcpu *vcpu)
pmu->nr_arch_fixed_counters =
min_t(int, edx.split.num_counters_fixed,
x86_pmu.num_counters_fixed);
+ edx.split.bit_width_fixed = min_t(int,
+ edx.split.bit_width_fixed, x86_pmu.bit_width_fixed);
pmu->counter_bitmask[KVM_PMC_FIXED] =
((u64)1 << edx.split.bit_width_fixed) - 1;
}
