Driver's probe allocates memory for RX FIFO (port->rx_fifo) based on default RX FIFO depth, e.g. 16. Later during serial startup the qcom_geni_serial_port_setup() updates the RX FIFO depth (port->rx_fifo_depth) to match real device capabilities, e.g. to 32.

The RX UART handle code will read "port->rx_fifo_depth" number of words into "port->rx_fifo" buffer, thus exceeding the bounds. This can be observed in certain configurations with Qualcomm Bluetooth HCI UART device and KASAN:

Bluetooth: hci0: QCA Product ID :0x00000010 Bluetooth: hci0: QCA SOC Version :0x400a0200 Bluetooth: hci0: QCA ROM Version :0x00000200 Bluetooth: hci0: QCA Patch Version:0x00000d2b Bluetooth: hci0: QCA controller version 0x02000200 Bluetooth: hci0: QCA Downloading qca/htbtfw20.tlv bluetooth hci0: Direct firmware load for qca/htbtfw20.tlv failed with error -2 Bluetooth: hci0: QCA Failed to request file: qca/htbtfw20.tlv (-2) Bluetooth: hci0: QCA Failed to download patch (-2) ================================================================== BUG: KASAN: slab-out-of-bounds in handle_rx_uart+0xa8/0x18c Write of size 4 at addr ffff279347d578c0 by task swapper/0/0

CPU: 0 PID: 0 Comm: swapper/0 Not tainted 6.1.0-rt5-00350-gb2450b7e00be-dirty #26 Hardware name: Qualcomm Technologies, Inc. Robotics RB5 (DT) Call trace: dump_backtrace.part.0+0xe0/0xf0 show_stack+0x18/0x40 dump_stack_lvl+0x8c/0xb8 print_report+0x188/0x488 kasan_report+0xb4/0x100 __asan_store4+0x80/0xa4 handle_rx_uart+0xa8/0x18c qcom_geni_serial_handle_rx+0x84/0x9c qcom_geni_serial_isr+0x24c/0x760 __handle_irq_event_percpu+0x108/0x500 handle_irq_event+0x6c/0x110 handle_fasteoi_irq+0x138/0x2cc generic_handle_domain_irq+0x48/0x64

If the RX FIFO depth changes after probe, be sure to resize the buffer.

Fixes: f9d690b6ece7 ("tty: serial: qcom_geni_serial: Allocate port->rx_fifo buffer in probe") Cc: stable@vger.kernel.org Signed-off-by: Krzysztof Kozlowski krzysztof.kozlowski@linaro.org Reviewed-by: Jiri Slaby jirislaby@kernel.org

---

Changes since v1: 1. Rename the function (Jiri) --- drivers/tty/serial/qcom_geni_serial.c | 18 ++++++++++++++++-- 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/qcom_geni_serial.c b/drivers/tty/serial/qcom_geni_serial.c index b487823f0e61..49b9ffeae676 100644 --- a/drivers/tty/serial/qcom_geni_serial.c +++ b/drivers/tty/serial/qcom_geni_serial.c @@ -864,9 +864,10 @@ static irqreturn_t qcom_geni_serial_isr(int isr, void *dev) return IRQ_HANDLED; }

-static void get_tx_fifo_size(struct qcom_geni_serial_port *port) +static int setup_fifos(struct qcom_geni_serial_port *port) { struct uart_port *uport; + u32 old_rx_fifo_depth = port->rx_fifo_depth;

uport = &port->uport; port->tx_fifo_depth = geni_se_get_tx_fifo_depth(&port->se); @@ -874,6 +875,16 @@ static void get_tx_fifo_size(struct qcom_geni_serial_port *port) port->rx_fifo_depth = geni_se_get_rx_fifo_depth(&port->se); uport->fifosize = (port->tx_fifo_depth * port->tx_fifo_width) / BITS_PER_BYTE; + + if (port->rx_fifo && (old_rx_fifo_depth != port->rx_fifo_depth) && port->rx_fifo_depth) { + port->rx_fifo = devm_krealloc(uport->dev, port->rx_fifo, + port->rx_fifo_depth * sizeof(u32), + GFP_KERNEL); + if (!port->rx_fifo) + return -ENOMEM; + } + + return 0; }

@@ -888,6 +899,7 @@ static int qcom_geni_serial_port_setup(struct uart_port *uport) u32 rxstale = DEFAULT_BITS_PER_CHAR * STALE_TIMEOUT; u32 proto; u32 pin_swap; + int ret;

proto = geni_se_read_proto(&port->se); if (proto != GENI_SE_UART) { @@ -897,7 +909,9 @@ static int qcom_geni_serial_port_setup(struct uart_port *uport)

qcom_geni_serial_stop_rx(uport);

- get_tx_fifo_size(port); + ret = setup_fifos(port); + if (ret) + return ret;

writel(rxstale, uport->membase + SE_UART_RX_STALE_CNT);