[PATCH 5.10 040/142] KVM: x86/pmu: Fix UBSAN shift-out-of-bounds warning in intel_pmu_refresh()

Greg Kroah-Hartman
2021-02-02T13:52:13Z

From: Like Xu <like.xu@linux.intel.com>

commit e61ab2a320c3dfd6209efe18a575979e07470597 upstream.

Since we know vPMU will not work properly when (1) the guest bit_width(s)
of the [gp|fixed] counters are greater than the host ones, or (2) guest
requested architectural events exceeds the range supported by the host, so
we can setup a smaller left shift value and refresh the guest 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@syzkaller.appspotmail.com
Signed-off-by: Like Xu <like.xu@linux.intel.com>
Message-Id: <20210118025800.34620-1-like.xu@linux.intel.com>
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/x86/kvm/vmx/pmu_intel.c | 4 ++++
1 file changed, 4 insertions(+)

--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -345,7 +345,9 @@ static void intel_pmu_refresh(struct kvm

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;
+ eax.split.mask_length = min_t(int, eax.split.mask_length, x86_pmu.events_mask_len);
pmu->available_event_types = ~entry->ebx &
((1ull << eax.split.mask_length) - 1);

@@ -355,6 +357,8 @@ static void intel_pmu_refresh(struct kvm
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;
}