hw/ssi/xilinx_spips: fix an out of bound access

The spips, qspips, and zynqmp-qspips share the same realize function
(xilinx_spips_realize) and initialize their io memory region with different
mmio_ops passed through the class.  The size of the memory region is set to
the largest area (0x200 bytes for zynqmp-qspips) thus it is possible to write
out of s->regs[addr] in xilinx_spips_write for spips and qspips.

This fixes that wrong behavior.

Reviewed-by: Luc Michel <luc.michel@amd.com>
Signed-off-by: Frederic Konrad <fkonrad@amd.com>
Reviewed-by: Francisco Iglesias <francisco.iglesias@amd.com>
Message-id: 20231124143505.1493184-2-fkonrad@amd.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

hw/ssi/xilinx_spips.c

@@ -973,6 +973,8 @@ static void xilinx_spips_write(void *opaque, hwaddr addr,
 
     DB_PRINT_L(0, "addr=" HWADDR_FMT_plx " = %x\n", addr, (unsigned)value);
     addr >>= 2;
+    assert(addr < XLNX_SPIPS_R_MAX);
+
     switch (addr) {
     case R_CONFIG:
         mask = ~(R_CONFIG_RSVD | MAN_START_COM);
@@ -1299,7 +1301,7 @@ static void xilinx_spips_realize(DeviceState *dev, Error **errp)
     }
 
     memory_region_init_io(&s->iomem, OBJECT(s), xsc->reg_ops, s,
-                          "spi", XLNX_ZYNQMP_SPIPS_R_MAX * 4);
+                          "spi", xsc->reg_size);
     sysbus_init_mmio(sbd, &s->iomem);
 
     s->irqline = -1;
@@ -1435,6 +1437,7 @@ static void xilinx_qspips_class_init(ObjectClass *klass, void * data)
 
     dc->realize = xilinx_qspips_realize;
     xsc->reg_ops = &qspips_ops;
+    xsc->reg_size = XLNX_SPIPS_R_MAX * 4;
     xsc->rx_fifo_size = RXFF_A_Q;
     xsc->tx_fifo_size = TXFF_A_Q;
 }
@@ -1450,6 +1453,7 @@ static void xilinx_spips_class_init(ObjectClass *klass, void *data)
     dc->vmsd = &vmstate_xilinx_spips;
 
     xsc->reg_ops = &spips_ops;
+    xsc->reg_size = XLNX_SPIPS_R_MAX * 4;
     xsc->rx_fifo_size = RXFF_A;
     xsc->tx_fifo_size = TXFF_A;
 }
@@ -1464,6 +1468,7 @@ static void xlnx_zynqmp_qspips_class_init(ObjectClass *klass, void * data)
     dc->vmsd = &vmstate_xlnx_zynqmp_qspips;
     device_class_set_props(dc, xilinx_zynqmp_qspips_properties);
     xsc->reg_ops = &xlnx_zynqmp_qspips_ops;
+    xsc->reg_size = XLNX_ZYNQMP_SPIPS_R_MAX * 4;
     xsc->rx_fifo_size = RXFF_A_Q;
     xsc->tx_fifo_size = TXFF_A_Q;
 }

include/hw/ssi/xilinx_spips.h

@@ -33,7 +33,9 @@
 
 typedef struct XilinxSPIPS XilinxSPIPS;
 
+/* For SPIPS, QSPIPS.  */
 #define XLNX_SPIPS_R_MAX        (0x100 / 4)
+/* For ZYNQMP_QSPIPS.  */
 #define XLNX_ZYNQMP_SPIPS_R_MAX (0x200 / 4)
 
 /* Bite off 4k chunks at a time */
@@ -125,6 +127,7 @@ struct XilinxSPIPSClass {
     SysBusDeviceClass parent_class;
 
     const MemoryRegionOps *reg_ops;
+    uint64_t reg_size;
 
     uint32_t rx_fifo_size;
     uint32_t tx_fifo_size;