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[88.207.42.168]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-427d68fa493sm36214095e9.10.2024.07.19.12.53.48 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 19 Jul 2024 12:53:49 -0700 (PDT) Message-ID: <34df3c7d-9f39-4878-80a9-72f5d2d858db@gmail.com> Date: Fri, 19 Jul 2024 21:53:45 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: =?UTF-8?Q?Re=3A_=5BBUG=5D_6=2E10_stable=3A_arch/x86/kvm/xen=2Ec=3A1?= =?UTF-8?Q?486=3A44=3A_error=3A_use_of_uninitialized_value_=E2=80=98port?= =?UTF-8?B?4oCZIFtDV0UtNDU3XQ==?= To: Sean Christopherson Cc: kvm@vger.kernel.org, Paolo Bonzini , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , linux-kernel@vger.kernel.org, Boris Ostrovsky References: <7b47f4b7-eda8-40e2-883c-6d6c539a4649@gmail.com> Content-Language: en-US From: Mirsad Todorovac In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 7/19/24 19:30, Sean Christopherson wrote: > On Fri, Jul 19, 2024, Mirsad Todorovac wrote: >> Hi, all, >> >> While building stable tree version of 6.10, the following error occurred: >> >> In line 1421 defines: >> >> 1421 evtchn_port_t port, *ports; >> >> The ports becomes &port in line 1470, but neither port nor *ports is assigned a value >> until line 1486 where port is used: >> >> 1485 if (sched_poll.nr_ports == 1) >> 1486 → vcpu->arch.xen.poll_evtchn = port; >> >> The visual inspection proves that the compiler is again right (GCC 12.3.0). > > Nope, the compiler is wrong. If sched_poll.nr_ports > 0, then kvm_read_guest_virt() > will fill ports[sched_poll.nr_ports]. If kvm_read_guest_virt() fails to do so, > it will return an error and the above code will never be reached. > > if (kvm_read_guest_virt(vcpu, (gva_t)sched_poll.ports, ports, > sched_poll.nr_ports * sizeof(*ports), &e)) { > *r = -EFAULT; > return true; > } Hi again, I see what you mean. Apparently, this dependency is not visible by the compiler, and this makes static analysers of dubious value ... I might need some advice on how to contribute to the Q/A of the kernel proper and testing suite ... Best regards, Mirsad Todorovac