pinctrl: single: fix infinite loop caused by bad mask

commit 4e7e8017a8 (pinctrl: pinctrl-single:
enhance to configure multiple pins of different modules) improved
support for pinctrl-single,bits option, but also caused a regression
in parsing badly configured mask data.

If the masks in DT data are not quite right,
pcs_parse_bits_in_pinctrl_entry() can end up in an infinite loop,
trashing memory at the same time.

Add a check to verify that each loop actually removes bits from the
'mask', so that the loop can eventually end.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/pinctrl/pinctrl-single.c

@@ -1318,6 +1318,14 @@ static int pcs_parse_bits_in_pinctrl_entry(struct pcs_device *pcs,
 			mask_pos = ((pcs->fmask) << (bit_pos - 1));
 			val_pos = val & mask_pos;
 			submask = mask & mask_pos;
+
+			if ((mask & mask_pos) == 0) {
+				dev_err(pcs->dev,
+					"Invalid mask for %s at 0x%x\n",
+					np->name, offset);
+				break;
+			}
+
 			mask &= ~mask_pos;
 
 			if (submask != mask_pos) {