Improved matching on global attributes for differential channels

Signed-off-by: fpagliughi <[email protected]>

local.c

@@ -1480,16 +1480,18 @@ static unsigned int is_global_attr(struct iio_channel *chn, const char *attr)
 
 	len = ptr - attr;
 
-	// Check if matching global differential attr,
-	// like "voltage-voltage"
+	// Check for matching global differential attr, like "voltage-voltage"
 	dashptr = strchr(attr, '-');
 	if (dashptr && dashptr > attr && dashptr < ptr) {
 		unsigned int len1 = dashptr - attr,
 					 len2 = ptr - dashptr - 1;
-		if (chn->id[len1] >= '0' && chn->id[len1] <= '9' &&
+		const char*  iddashptr = strchr(chn->id, '-');
+		if (iddashptr && strlen(iddashptr+1) > len2 &&
+			iddashptr - chn->id > len1 &&
+			chn->id[len1] >= '0' && chn->id[len1] <= '9' &&
 			!strncmp(chn->id, attr, len1) &&
-			chn->id[len+1] >= '0' && chn->id[len+1] <= '9' &&
-			!strncmp(chn->id+len1+2, attr+len1+1, len2))
+			iddashptr[len2+1] >= '0' && iddashptr[len2+1] <= '9' &&
+			!strncmp(iddashptr+1, dashptr+1, len2))
 			return 1;
 	}