iio: core: Use scnprintf() for avoiding potential buffer overflow

Since snprintf() returns the would-be-output size instead of the
actual output size, the succeeding calls may go beyond the given
buffer limit.  Fix it by replacing with scnprintf().
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/industrialio-core.c

@@ -566,46 +566,46 @@ static ssize_t __iio_format_value(char *buf, size_t len, unsigned int type,
 
 	switch (type) {
 	case IIO_VAL_INT:
-		return snprintf(buf, len, "%d", vals[0]);
+		return scnprintf(buf, len, "%d", vals[0]);
 	case IIO_VAL_INT_PLUS_MICRO_DB:
 		scale_db = true;
 		/* fall through */
 	case IIO_VAL_INT_PLUS_MICRO:
 		if (vals[1] < 0)
-			return snprintf(buf, len, "-%d.%06u%s", abs(vals[0]),
+			return scnprintf(buf, len, "-%d.%06u%s", abs(vals[0]),
 					-vals[1], scale_db ? " dB" : "");
 		else
-			return snprintf(buf, len, "%d.%06u%s", vals[0], vals[1],
+			return scnprintf(buf, len, "%d.%06u%s", vals[0], vals[1],
 					scale_db ? " dB" : "");
 	case IIO_VAL_INT_PLUS_NANO:
 		if (vals[1] < 0)
-			return snprintf(buf, len, "-%d.%09u", abs(vals[0]),
+			return scnprintf(buf, len, "-%d.%09u", abs(vals[0]),
 					-vals[1]);
 		else
-			return snprintf(buf, len, "%d.%09u", vals[0], vals[1]);
+			return scnprintf(buf, len, "%d.%09u", vals[0], vals[1]);
 	case IIO_VAL_FRACTIONAL:
 		tmp = div_s64((s64)vals[0] * 1000000000LL, vals[1]);
 		tmp1 = vals[1];
 		tmp0 = (int)div_s64_rem(tmp, 1000000000, &tmp1);
-		return snprintf(buf, len, "%d.%09u", tmp0, abs(tmp1));
+		return scnprintf(buf, len, "%d.%09u", tmp0, abs(tmp1));
 	case IIO_VAL_FRACTIONAL_LOG2:
 		tmp = shift_right((s64)vals[0] * 1000000000LL, vals[1]);
 		tmp0 = (int)div_s64_rem(tmp, 1000000000LL, &tmp1);
-		return snprintf(buf, len, "%d.%09u", tmp0, abs(tmp1));
+		return scnprintf(buf, len, "%d.%09u", tmp0, abs(tmp1));
 	case IIO_VAL_INT_MULTIPLE:
 	{
 		int i;
 		int l = 0;
 
 		for (i = 0; i < size; ++i) {
-			l += snprintf(&buf[l], len - l, "%d ", vals[i]);
+			l += scnprintf(&buf[l], len - l, "%d ", vals[i]);
 			if (l >= len)
 				break;
 		}
 		return l;
 	}
 	case IIO_VAL_CHAR:
-		return snprintf(buf, len, "%c", (char)vals[0]);
+		return scnprintf(buf, len, "%c", (char)vals[0]);
 	default:
 		return 0;
 	}
@@ -676,10 +676,10 @@ static ssize_t iio_format_avail_list(char *buf, const int *vals,
 			if (len >= PAGE_SIZE)
 				return -EFBIG;
 			if (i < length - 1)
-				len += snprintf(buf + len, PAGE_SIZE - len,
+				len += scnprintf(buf + len, PAGE_SIZE - len,
 						" ");
 			else
-				len += snprintf(buf + len, PAGE_SIZE - len,
+				len += scnprintf(buf + len, PAGE_SIZE - len,
 						"\n");
 			if (len >= PAGE_SIZE)
 				return -EFBIG;
@@ -692,10 +692,10 @@ static ssize_t iio_format_avail_list(char *buf, const int *vals,
 			if (len >= PAGE_SIZE)
 				return -EFBIG;
 			if (i < length / 2 - 1)
-				len += snprintf(buf + len, PAGE_SIZE - len,
+				len += scnprintf(buf + len, PAGE_SIZE - len,
 						" ");
 			else
-				len += snprintf(buf + len, PAGE_SIZE - len,
+				len += scnprintf(buf + len, PAGE_SIZE - len,
 						"\n");
 			if (len >= PAGE_SIZE)
 				return -EFBIG;
@@ -719,10 +719,10 @@ static ssize_t iio_format_avail_range(char *buf, const int *vals, int type)
 			if (len >= PAGE_SIZE)
 				return -EFBIG;
 			if (i < 2)
-				len += snprintf(buf + len, PAGE_SIZE - len,
+				len += scnprintf(buf + len, PAGE_SIZE - len,
 						" ");
 			else
-				len += snprintf(buf + len, PAGE_SIZE - len,
+				len += scnprintf(buf + len, PAGE_SIZE - len,
 						"]\n");
 			if (len >= PAGE_SIZE)
 				return -EFBIG;
@@ -735,10 +735,10 @@ static ssize_t iio_format_avail_range(char *buf, const int *vals, int type)
 			if (len >= PAGE_SIZE)
 				return -EFBIG;
 			if (i < 2)
-				len += snprintf(buf + len, PAGE_SIZE - len,
+				len += scnprintf(buf + len, PAGE_SIZE - len,
 						" ");
 			else
-				len += snprintf(buf + len, PAGE_SIZE - len,
+				len += scnprintf(buf + len, PAGE_SIZE - len,
 						"]\n");
 			if (len >= PAGE_SIZE)
 				return -EFBIG;