[PATCH] tty: serial: mpc52xx_uart: add bounds check for psc_num array index

[Rosen Penev]

psc_num is derived from port->mapbase bits 11:8, giving a range of
0-15, but the psc_mclk_clk and psc_ipg_clk arrays are sized to
MPC52xx_PSC_MAXNUM (12 when CONFIG_PPC_MPC512x is set). A malformed
device tree with bits 11:8 >= 12 would cause out-of-bounds writes
in mpc512x_psc_alloc_clock() and out-of-bounds reads/writes in
mpc512x_psc_relse_clock() and mpc512x_psc_endis_clock(). The same
unchecked index also appears in mpc512x_psc_handle_irq().

Add ARRAY_SIZE() bounds checks to all four functions before using
psc_num as an array index.

Assisted-by: Opencode:big-pickle
Signed-off-by: Rosen Penev <rosenp@xxxxxxxxx>
---
 drivers/tty/serial/mpc52xx_uart.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/tty/serial/mpc52xx_uart.c b/drivers/tty/serial/mpc52xx_uart.c
index 37eb701b0b46..b566206f42a2 100644
--- a/drivers/tty/serial/mpc52xx_uart.c
+++ b/drivers/tty/serial/mpc52xx_uart.c
@@ -645,6 +645,8 @@ static irqreturn_t mpc512x_psc_handle_irq(struct uart_port *port)
 
 	/* Check if it is an interrupt for this port */
 	psc_num = (port->mapbase & 0xf00) >> 8;
+	if (psc_num >= ARRAY_SIZE(psc_mclk_clk))
+		return IRQ_NONE;
 	if (test_bit(psc_num, &fifoc_int) ||
 	    test_bit(psc_num + 16, &fifoc_int))
 		return mpc5xxx_uart_process_int(port);
@@ -663,6 +665,8 @@ static int mpc512x_psc_alloc_clock(struct uart_port *port)
 	int err;
 
 	psc_num = (port->mapbase & 0xf00) >> 8;
+	if (psc_num >= ARRAY_SIZE(psc_mclk_clk))
+		return -EINVAL;
 
 	clk = devm_clk_get(port->dev, "mclk");
 	if (IS_ERR(clk)) {
@@ -711,6 +715,8 @@ static void mpc512x_psc_relse_clock(struct uart_port *port)
 	struct clk *clk;
 
 	psc_num = (port->mapbase & 0xf00) >> 8;
+	if (psc_num >= ARRAY_SIZE(psc_mclk_clk))
+		return;
 	clk = psc_mclk_clk[psc_num];
 	if (clk) {
 		clk_disable_unprepare(clk);
@@ -733,6 +739,8 @@ static int mpc512x_psc_endis_clock(struct uart_port *port, int enable)
 		return 0;
 
 	psc_num = (port->mapbase & 0xf00) >> 8;
+	if (psc_num >= ARRAY_SIZE(psc_mclk_clk))
+		return -ENODEV;
 	psc_clk = psc_mclk_clk[psc_num];
 	if (!psc_clk) {
 		dev_err(port->dev, "Failed to get PSC clock entry!\n");
-- 
2.54.0