From: Like Xu <like.xu@linux.intel.com>
To: Paolo Bonzini <pbonzini@redhat.com>,
Sean Christopherson <sean.j.christopherson@intel.com>
Cc: syzkaller-bugs@googlegroups.com,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
kvm@vger.kernel.org, Wanpeng Li <wanpengli@tencent.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] KVM: x86/pmu: Fix UBSAN shift-out-of-bounds warning in intel_pmu_refresh()
Date: Fri, 15 Jan 2021 16:47:27 +0800 [thread overview]
Message-ID: <fb60e9b1-0d96-a1a7-1828-80d6e2c21e0c@linux.intel.com> (raw)
In-Reply-To: <20201229071144.85418-1-like.xu@linux.intel.com>
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@syzkaller.appspotmail.com
> Signed-off-by: Like Xu <like.xu@linux.intel.com>
> ---
> 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;
> }
next prev parent reply other threads:[~2021-01-15 8:49 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-29 7:11 [PATCH] KVM: x86/pmu: Fix UBSAN shift-out-of-bounds warning in intel_pmu_refresh() Like Xu
2021-01-15 8:47 ` Like Xu [this message]
2021-01-16 0:16 ` Sean Christopherson
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