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([2001:41d0:a04:2e00::]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-45491ca2fd6sm11224669f8f.30.2026.05.09.02.46.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 09 May 2026 02:46:09 -0700 (PDT) From: Florian Pradines To: gupt21@gmail.com, jikos@kernel.org, bentiss@kernel.org Cc: linux-i2c@vger.kernel.org, linux-input@vger.kernel.org, Florian Pradines Subject: [PATCH] HID: mcp2221: fix OOB write in mcp2221_raw_event() Date: Sat, 9 May 2026 09:45:17 +0000 Message-ID: <20260509094517.2691246-1-florian.pradines@gmail.com> X-Mailer: git-send-email 2.47.3 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() copies device-supplied data into mcp->rxbuf at offset rxbuf_idx without checking that the copy fits within the destination buffer. A device responding with up to 60 bytes to a small I2C/SMBus read can overflow the buffer. Add a rxbuf_size field to struct mcp2221, set it alongside rxbuf in mcp_i2c_smbus_read(), and check rxbuf_idx + data[3] <= rxbuf_size before the memcpy. Signed-off-by: Florian Pradines --- drivers/hid/hid-mcp2221.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/drivers/hid/hid-mcp2221.c b/drivers/hid/hid-mcp2221.c index be80970ab48e..e4ddd8e9293b 100644 --- a/drivers/hid/hid-mcp2221.c +++ b/drivers/hid/hid-mcp2221.c @@ -128,6 +128,7 @@ struct mcp2221 { u8 *rxbuf; u8 txbuf[64]; int rxbuf_idx; + int rxbuf_size; int status; u8 cur_i2c_clk_div; struct gpio_chip *gc; @@ -330,12 +331,14 @@ static int mcp_i2c_smbus_read(struct mcp2221 *mcp, mcp->txbuf[3] = (u8)(msg->addr << 1); total_len = msg->len; mcp->rxbuf = msg->buf; + mcp->rxbuf_size = msg->len; } else { mcp->txbuf[1] = smbus_len; mcp->txbuf[2] = 0; mcp->txbuf[3] = (u8)(smbus_addr << 1); total_len = smbus_len; mcp->rxbuf = smbus_buf; + mcp->rxbuf_size = smbus_len; } ret = mcp_send_data_req_status(mcp, mcp->txbuf, 4); @@ -919,6 +922,10 @@ static int mcp2221_raw_event(struct hid_device *hdev, mcp->status = -EINVAL; break; } + if (mcp->rxbuf_idx + data[3] > mcp->rxbuf_size) { + mcp->status = -EINVAL; + break; + } buf = mcp->rxbuf; memcpy(&buf[mcp->rxbuf_idx], &data[4], data[3]); mcp->rxbuf_idx = mcp->rxbuf_idx + data[3]; -- 2.47.3