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[82.218.84.190]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-5cee6a9a41bsm1467773a12.14.2024.11.05.08.00.54 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Tue, 05 Nov 2024 08:00:55 -0800 (PST) From: Phil Dennis-Jordan To: qemu-devel@nongnu.org Cc: dirty@apple.com, rbolshakov@ddn.com, pbonzini@redhat.com, Phil Dennis-Jordan Subject: [PATCH 2/5] i386/hvf: Fix for UB in handling CPUID function 0xD Date: Tue, 5 Nov 2024 16:57:57 +0100 Message-Id: <20241105155800.5461-3-phil@philjordan.eu> X-Mailer: git-send-email 2.39.3 (Apple Git-145) In-Reply-To: <20241105155800.5461-1-phil@philjordan.eu> References: <20241105155800.5461-1-phil@philjordan.eu> MIME-Version: 1.0 Received-SPF: neutral client-ip=2a00:1450:4864:20::52e; envelope-from=phil@philjordan.eu; helo=mail-ed1-x52e.google.com X-Spam_score_int: -10 X-Spam_score: -1.1 X-Spam_bar: - X-Spam_report: (-1.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_NEUTRAL=0.779 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org The handling for CPUID function 0xD (supported XSAVE features) was improved in a recent patch. Unfortunately, this appears to have introduced undefined behaviour for cases where ecx > 30, as the result of (1 << idx) is undefined if idx > 30. Per Intel SDM section 13.2, the behaviour for ecx values up to and including 62 are specified. This change therefore specifically sets all registers returned by the CPUID instruction to 0 for 63 and higher. Furthermore, the bit shift uses uint64_t, where behaviour for the entire range of 2..62 is safe and correct. Signed-off-by: Phil Dennis-Jordan --- target/i386/hvf/x86_cpuid.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/target/i386/hvf/x86_cpuid.c b/target/i386/hvf/x86_cpuid.c index ac922d7fd16..9d9ccaa815d 100644 --- a/target/i386/hvf/x86_cpuid.c +++ b/target/i386/hvf/x86_cpuid.c @@ -119,8 +119,8 @@ uint32_t hvf_get_supported_cpuid(uint32_t func, uint32_t idx, eax = 0; break; case 0xD: - if (!supported_xcr0 || - (idx > 1 && !(supported_xcr0 & (1 << idx)))) { + if (!supported_xcr0 || idx >= 63 || + (idx > 1 && !(supported_xcr0 & (UINT64_C(1) << idx)))) { eax = ebx = ecx = edx = 0; break; }