[Qemu-devel] [PATCH v2 1/1] cadence_uart: Check baud rate generator and divider values on migration

[Alistair Francis]

The Cadence UART device emulator calculates speed by dividing the
baud rate by a 'baud rate generator' & 'baud rate divider' value.
The device specification defines these register values to be
non-zero and within certain limits. Checks were recently added when
writing to these registers but not when restoring from migration.

This patch adds checks when restoring from migration to avoid divide by
zero errors.

Reported-by: Huawei PSIRT <address@hidden>
Signed-off-by: Alistair Francis <address@hidden>
---
V2:
 - Abort the migration if the data is invalid

 hw/char/cadence_uart.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/hw/char/cadence_uart.c b/hw/char/cadence_uart.c
index def34cd..9568ac6 100644
--- a/hw/char/cadence_uart.c
+++ b/hw/char/cadence_uart.c
@@ -487,6 +487,13 @@ static int cadence_uart_post_load(void *opaque, int 
version_id)
 {
     CadenceUARTState *s = opaque;
 
+    /* Ensure these two aren't invalid numbers */
+    if (s->r[R_BRGR] <= 1 || s->r[R_BRGR] & 0xFFFF ||
+        s->r[R_BDIV] <= 3 || s->r[R_BDIV] & 0xFF) {
+        /* Value is invalid, abort */
+        return 1;
+    }
+
     uart_parameters_setup(s);
     uart_update_status(s);
     return 0;
-- 
2.7.4