wifi: mwifiex: handle possible sscanf() errors

Return -EINVAL on possible 'sscanf()' errors in
'mwifiex_regrdwr_write()' and 'mwifiex_rdeeprom_write()'.

Found by Linux Verification Center (linuxtesting.org) with SVACE.
Acked-by: Brian Norris <briannorris@chromium.org>
Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20230802160726.85545-3-dmantipov@yandex.ru

drivers/net/wireless/marvell/mwifiex/debugfs.c

@@ -425,7 +425,10 @@ mwifiex_regrdwr_write(struct file *file,
 	if (IS_ERR(buf))
 		return PTR_ERR(buf);
 
-	sscanf(buf, "%u %x %x", &reg_type, &reg_offset, &reg_value);
+	if (sscanf(buf, "%u %x %x", &reg_type, &reg_offset, &reg_value) != 3) {
+		ret = -EINVAL;
+		goto done;
+	}
 
 	if (reg_type == 0 || reg_offset == 0) {
 		ret = -EINVAL;
@@ -691,7 +694,10 @@ mwifiex_rdeeprom_write(struct file *file,
 	if (IS_ERR(buf))
 		return PTR_ERR(buf);
 
-	sscanf(buf, "%d %d", &offset, &bytes);
+	if (sscanf(buf, "%d %d", &offset, &bytes) != 2) {
+		ret = -EINVAL;
+		goto done;
+	}
 
 	if (offset == -1 || bytes == -1) {
 		ret = -EINVAL;