[Qemu-arm] [PATCH] char: cadence: check divider against baud rate

[P J P]

From: Prasad J Pandit <address@hidden>

The Cadence UART device emulator calculates speed by dividing the
baud rate by a divider. If this divider was to be zero or if baud
rate was to be lesser than the divider, it could lead to a divide
by zero error. Add check to avoid it.

Reported-by: Huawei PSIRT <address@hidden>
Signed-off-by: Prasad J Pandit <address@hidden>
---
 hw/char/cadence_uart.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/hw/char/cadence_uart.c b/hw/char/cadence_uart.c
index e3bc52f..b18dd7f 100644
--- a/hw/char/cadence_uart.c
+++ b/hw/char/cadence_uart.c
@@ -170,6 +170,10 @@ static void uart_parameters_setup(CadenceUARTState *s)
     baud_rate = (s->r[R_MR] & UART_MR_CLKS) ?
             UART_INPUT_CLK / 8 : UART_INPUT_CLK;
 
+    if (!s->r[R_BRGR] || !(s->r[R_BDIV] + 1)
+        || baud_rate < (s->r[R_BRGR] * (s->r[R_BDIV] + 1))) {
+        return;
+    }
     ssp.speed = baud_rate / (s->r[R_BRGR] * (s->r[R_BDIV] + 1));
     packet_size = 1;
 
-- 
2.7.4