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([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.gmail.com with ESMTPSA id k10sm1382488ejo.117.2021.09.29.05.57.34 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 29 Sep 2021 05:57:35 -0700 (PDT) Message-ID: Date: Wed, 29 Sep 2021 14:57:32 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.1.0 Subject: Re: [PATCH 0/2] Fix wild/dangling pointer in x86 ptp_kvm Content-Language: en-US To: Zelin Deng , Thomas Gleixner Cc: x86@kernel.org, kvm@vger.kernel.org, stable@vger.kernel.org References: <1632892429-101194-1-git-send-email-zelin.deng@linux.alibaba.com> From: Paolo Bonzini In-Reply-To: <1632892429-101194-1-git-send-email-zelin.deng@linux.alibaba.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 29/09/21 07:13, Zelin Deng wrote: > When I was doing PTP_SYS_OFFSET_PRECISE ioctl in VM which has 128 vCPUs, > I got error returned occasionally. Then I checked the routine of > "getcrosststamp". I found in kvm_arch_ptp_get_crosststamp() of x86, > pvclock vcpu time info was got from hv_clock arrary which has only 64 > elements. Hence this ioctl is executed on vCPU > 64, a wild/dangling > pointer will be got, which had casued the error. > To confirm this finding, I wrote a simple PTP_SYS_OFFSET_PRECISE ioctl > test and used "taskset -c n" to run the test, when it was executed on > vCPUs >= 64 it returned error. > This patchset exposes this_cpu_pvti() to get per cpu pvclock vcpu time > info of vCPUs >= 64 insdead of getting them from hv_clock arrary. > > Zelin Deng (2): > x86/kvmclock: Move this_cpu_pvti into kvmclock.h > ptp: Fix ptp_kvm_getcrosststamp issue for x86 ptp_kvm > > arch/x86/include/asm/kvmclock.h | 14 ++++++++++++++ > arch/x86/kernel/kvmclock.c | 13 ++----------- > drivers/ptp/ptp_kvm_x86.c | 9 ++------- > 3 files changed, 18 insertions(+), 18 deletions(-) > Queued, thanks. Paolo