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Tue, 03 Nov 2026 10:48:35 -0800 (PST) Received: from google.com ([2a00:79e0:2ebe:8:88b4:22ec:d621:c1b]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-36ca39b3b7esm11574eec.28.2026.11.03.10.48.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 03 Nov 2026 10:48:34 -0800 (PST) Date: Tue, 3 Nov 2026 10:48:31 -0800 From: Dmitry Torokhov To: Chengyu Liu Cc: linux-input@vger.kernel.org Subject: Re: [PATCH 0/2] Input: clamp SMBus block reads to the caller's buffer Message-ID: References: <20261103131127.1585884-1-lui2012qwq@gmail.com> X-Mailing-List: linux-input@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261103131127.1585884-1-lui2012qwq@gmail.com> Hi Chengyu, On Tue, Nov 03, 2026 at 09:11:25PM +0800, Chengyu Liu wrote: > i2c_smbus_read_block_data() has no length parameter: it copies the > device-reported byte count (clamped to I2C_SMBUS_BLOCK_MAX by the > core) into the caller's buffer, so callers must pass a full-size > buffer. An audit of all call sites found two input drivers passing > smaller stack buffers: > > - rmi4: rmi_read_pdt_entry() reads PDT entries into a 6-byte stack > buffer during PDT scanning at probe time; a device reporting a > count of 32 overruns it by 26 bytes. > > - cyapa: cyapa_gen3_irq_handler() reads into a 27-byte struct > cyapa_reg_data on every touch interrupt; a count of 32 overruns it > by 5 bytes, in interrupt context. > > In both cases the contents are controlled by the device. Bounce the > reads through a full-size buffer and clamp the copy to the requested > length. No, we should be using the new 4-argument variant of i2c_smbus_read_block_data() that I posted earlier. Thanks. -- Dmitry