xilinx-ams: Fix UBSan Warning

The issue was that a 64 bit datatype was being left shifted by
more than 63 bits due to the scan index of the AMS control
channels.

There is no functional need for these control channels to be
included in the scan_mask. This leads to the fix being a
range check on the scan index before shifting.

Addresses-UBSAN: shift-out-of-bounds
Signed-off-by: Conall O'Griofa <conall.o'griofa@xilinx.com>
State: pending

drivers/iio/adc/xilinx-ams.c

@@ -178,7 +178,8 @@ static void ams_enable_channel_sequence(struct ams *ams)
 	/* Run calibration of PS & PL as part of the sequence */
 	scan_mask = 1 | (1 << PS_SEQ_MAX);
 	for (i = 0; i < indio_dev->num_channels; i++)
-		scan_mask |= BIT(indio_dev->channels[i].scan_index);
+		if (indio_dev->channels[i].scan_index < PL_SEQ_MAX)
+			scan_mask |= BIT(indio_dev->channels[i].scan_index);
 
 	if (ams->ps_base) {
 		/* put sysmon in a soft reset to change the sequence */

drivers/iio/adc/xilinx-ams.h

@@ -193,6 +193,8 @@ enum ams_ps_pl_seq {
 #define PS_SEQ(x)           (x)
 #define PL_SEQ(x)           (PS_SEQ_MAX + x)
 
+#define PL_SEQ_MAX	((AMS_SEQ_MAX * 2) + 16U) /* PS Slot + PL Slot + 16 VAUX Channels */
+
 #define AMS_CHAN_TEMP(_scan_index, _addr, _ext) { \
 	.type = IIO_TEMP, \
 	.indexed = 1, \