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Mon, 27 Apr 2026 19:46:27 +0000 (UTC) Received: from localhost (unknown [10.44.24.6]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 781A7300070A; Mon, 27 Apr 2026 19:46:25 +0000 (UTC) From: =?utf-8?q?Marc-Andr=C3=A9_Lureau?= Date: Mon, 27 Apr 2026 23:42:39 +0400 Subject: [PATCH 40/41] hw/i2c/pmbus: fix undefined behavior in pmbus_direct_mode2data MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit Message-Id: <20260427-qom-tests-v1-40-c413f3605311@redhat.com> References: <20260427-qom-tests-v1-0-c413f3605311@redhat.com> In-Reply-To: <20260427-qom-tests-v1-0-c413f3605311@redhat.com> To: qemu-devel@nongnu.org Cc: armbru@redhat.com, =?utf-8?q?Marc-Andr=C3=A9_Lureau?= , Titus Rwantare X-Developer-Signature: v=1; a=openpgp-sha256; l=1137; i=marcandre.lureau@redhat.com; h=from:subject:message-id; bh=2dC++hVlKU9GL8wkcDvF8pRIuTJVc02X3ZdB8ioXtmc=; b=owEBbQKS/ZANAwAKAdro4Ql1lpzlAcsmYgBp77wWCSMLWSFlL5vt4DE7S0EM5qpi04Dpc02qu p6FV0ylYJOJAjMEAAEKAB0WIQSHqb2TP4fGBtJ29i3a6OEJdZac5QUCae+8FgAKCRDa6OEJdZac 5aqGEACx0uhHWEOvrKH+OM/eJnMfLtK/oZ2FIQ06+ockve3mGc8evJRD6BiAD6iCEwLqKCuxT/J A4YMSPcegVtKYcFNcPYGogfeMIQ3KWDKOhuOmXHBCh2EBlEABp60YnPFb93dMCwbD3LsSllmP/2 WXGMoAOmoHM7LPRulsKa6AFsQYZbrehZcJYt+cXwDpKa0rMJUHGs1VQ8PQBhDsJRCESEfGgPDhi dtsO1SX3ILQOQ7fValcvDFkKWxVNnXdKq5EfTKKy+VzT5bAisceOddWJsPcdHT5GIoBQLaz0K6/ ZbapY7KqiC5yDY4hF84hz9aeeK6Ar8zOOmo+wnkYvr3C1Bs489Unpli9Uk2BJZGeZPvkfTncgM+ U286pHCRVv+0Ngi91sNuB9Qrf/rvlDAQelxUimNZPj73Vu7qpJpzJK8vAutlLGKwBf8IM4hTEqy F0Wdcg6qJUiqtPhYWi5ZS6+PO9QIF5H+7+1iu7EDqs3vukoA7U2VV+7KMCd/x2LeI41H/yu0SK+ PL10FcYWCS6Kok/b2djb7SMv2X2m1yxakQspVPnc6UaXuFdYDZURwSgGu7nI7rdOBQyb9/GDNnb 1iwKqkTWmdd/Bs7GbtwDDEH44myq5pLgWDg7EXrpeI9koKc3ANE2cQlt96CWUHthMLvnLr15kMi n630XJ939sJxjXA== X-Developer-Key: i=marcandre.lureau@redhat.com; a=openpgp; fpr=87A9BD933F87C606D276F62DDAE8E10975969CE5 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 Received-SPF: pass client-ip=170.10.133.124; envelope-from=marcandre.lureau@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development 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 intermediate result of (Y * 10^-R - b) / m can be negative when the bias (b) is large and the raw register value is small (e.g. zero on an uninitialized device). Assigning that negative double to uint32_t is undefined behavior, caught by UBSan/clang. Use a double intermediate and clamp negative results to zero. Fixes: 3746d5c15e70 ("hw/i2c: add support for PMBus") Signed-off-by: Marc-André Lureau --- hw/i2c/pmbus_device.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/hw/i2c/pmbus_device.c b/hw/i2c/pmbus_device.c index 853dc4b4342..861f5b4fb63 100644 --- a/hw/i2c/pmbus_device.c +++ b/hw/i2c/pmbus_device.c @@ -23,8 +23,8 @@ uint16_t pmbus_data2direct_mode(PMBusCoefficients c, uint32_t value) uint32_t pmbus_direct_mode2data(PMBusCoefficients c, uint16_t value) { /* X = (Y * 10^-R - b) / m */ - uint32_t x = (value / pow(10, c.R) - c.b) / c.m; - return x; + double x = (value / pow(10, c.R) - c.b) / c.m; + return (x > 0) ? (uint32_t)x : 0; } uint16_t pmbus_data2linear_mode(uint16_t value, int exp) -- 2.53.0