cxl/region: prevent underflow in ways_to_cxl()

The "ways" variable comes from the user.  The ways_to_cxl() function
has an upper bound but it doesn't check for negatives.  Make
the "ways" variable an unsigned int to fix this bug.

Fixes: 80d10a6c ("cxl/region: Add interleave geometry attributes")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/Yueo3NV2hFCXx1iV@kili
[djbw: fixup interleave_ways_store() to only accept unsigned input]
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/cxl/core/region.c

@@ -319,10 +319,11 @@ static ssize_t interleave_ways_store(struct device *dev,
 	struct cxl_decoder *cxld = &cxlrd->cxlsd.cxld;
 	struct cxl_region *cxlr = to_cxl_region(dev);
 	struct cxl_region_params *p = &cxlr->params;
-	int rc, val, save;
+	unsigned int val, save;
+	int rc;
 	u8 iw;
 
-	rc = kstrtoint(buf, 0, &val);
+	rc = kstrtouint(buf, 0, &val);
 	if (rc)
 		return rc;
 

drivers/cxl/cxl.h

@@ -102,7 +102,7 @@ static inline int granularity_to_cxl(int g, u16 *ig)
 	return 0;
 }
 
-static inline int ways_to_cxl(int ways, u8 *iw)
+static inline int ways_to_cxl(unsigned int ways, u8 *iw)
 {
 	if (ways > 16)
 		return -EINVAL;