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Tue, 24 Mar 2026 10:06:11 -0700 (PDT) From: Sebastian Josue Alba Vives To: gupt21@gmail.com, jikos@kernel.org, bentiss@kernel.org Cc: linux-i2c@vger.kernel.org, linux-input@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Sebastian Josue Alba Vives Subject: [PATCH v2] HID: mcp2221: validate report size in raw_event handler Date: Tue, 24 Mar 2026 11:06:06 -0600 Message-ID: <20260324170606.5407-1-sebasjosue84@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260324062403.341855-1-sebasjosue84@gmail.com> References: <20260324062403.341855-1-sebasjosue84@gmail.com> Precedence: bulk X-Mailing-List: linux-input@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit mcp2221_raw_event() accesses the data buffer at offsets up to 55 without validating the size parameter. Since __hid_input_report() invokes the driver's raw_event callback before hid_report_raw_event() performs its own report-size validation, a device sending a truncated HID report can cause out-of-bounds heap reads in the kernel. The most critical access is the memcpy from data[50] into mcp->adc_values (6 bytes) when CONFIG_IIO is reachable. Other unchecked accesses include data[20] and a memcpy at data[22]. Additionally, a memcpy with device-controlled length (data[3], up to 60 bytes) from data[4] does not verify that size is large enough to cover the copy. MCP2221 devices use 64-byte HID reports. Add a check at the top of the handler to reject any report shorter than expected, and log a warning to aid debugging. Cc: stable@vger.kernel.org Signed-off-by: Sebastian Josue Alba Vives --- drivers/hid/hid-mcp2221.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/drivers/hid/hid-mcp2221.c b/drivers/hid/hid-mcp2221.c index ef3b5c77c..770c305d8 100644 --- a/drivers/hid/hid-mcp2221.c +++ b/drivers/hid/hid-mcp2221.c @@ -850,6 +850,11 @@ static int mcp2221_raw_event(struct hid_device *hdev, { u8 *buf; struct mcp2221 *mcp = hid_get_drvdata(hdev); + /* MCP2221 always sends 64-byte reports */ + if (size < 64) { + hid_warn(hdev, "report too short: %d < 64\n", size); + return 0; + } switch (data[0]) { -- 2.43.0