[PATCH 5.10.y 1/3] PCI/sysfs: Rely on lengths from scnprintf(), dsm_label_utf16s_to_utf8s()

[Sasha Levin <sashal@kernel.org>]

From: Krzysztof Wilczyński <kw@linux.com>

[ Upstream commit 316ae33051215f92c72fe13bc1bfc4e513a26700 ]

scnprintf() returns the number of bytes written into the buffer.  Change
dsm_label_utf16s_to_utf8s() to do the same.  Rely on those values instead
of using strlen() to compute the buffer length.

No functional change intended.

[bhelgaas: reorder patch in series, len++ to include newline added by
dsm_label_utf16s_to_utf8s(), commit log]
Link: https://lore.kernel.org/r/20210603000112.703037-3-kw@linux.com
Signed-off-by: Krzysztof Wilczyński <kw@linux.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
Stable-dep-of: dcc5bec09e23 ("PCI: Allow per function PCI slots to fix slot reset on s390")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/pci/pci-label.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/drivers/pci/pci-label.c b/drivers/pci/pci-label.c
index 6c406453b49f4..a24d28414f3a2 100644
--- a/drivers/pci/pci-label.c
+++ b/drivers/pci/pci-label.c
@@ -154,14 +154,17 @@ enum acpi_attr_enum {
 	ACPI_ATTR_INDEX_SHOW,
 };
 
-static void dsm_label_utf16s_to_utf8s(union acpi_object *obj, char *buf)
+static int dsm_label_utf16s_to_utf8s(union acpi_object *obj, char *buf)
 {
 	int len;
+
 	len = utf16s_to_utf8s((const wchar_t *)obj->buffer.pointer,
 			      obj->buffer.length,
 			      UTF16_LITTLE_ENDIAN,
 			      buf, PAGE_SIZE - 1);
-	buf[len] = '\n';
+	buf[len++] = '\n';
+
+	return len;
 }
 
 static int dsm_get_label(struct device *dev, char *buf,
@@ -169,7 +172,7 @@ static int dsm_get_label(struct device *dev, char *buf,
 {
 	acpi_handle handle;
 	union acpi_object *obj, *tmp;
-	int len = -1;
+	int len = 0;
 
 	handle = ACPI_HANDLE(dev);
 	if (!handle)
@@ -191,20 +194,19 @@ static int dsm_get_label(struct device *dev, char *buf,
 		 * this entry must return a null string.
 		 */
 		if (attr == ACPI_ATTR_INDEX_SHOW) {
-			scnprintf(buf, PAGE_SIZE, "%llu\n", tmp->integer.value);
+			len = scnprintf(buf, PAGE_SIZE, "%llu\n", tmp->integer.value);
 		} else if (attr == ACPI_ATTR_LABEL_SHOW) {
 			if (tmp[1].type == ACPI_TYPE_STRING)
-				scnprintf(buf, PAGE_SIZE, "%s\n",
+				len = scnprintf(buf, PAGE_SIZE, "%s\n",
 					  tmp[1].string.pointer);
 			else if (tmp[1].type == ACPI_TYPE_BUFFER)
-				dsm_label_utf16s_to_utf8s(tmp + 1, buf);
+				len = dsm_label_utf16s_to_utf8s(tmp + 1, buf);
 		}
-		len = strlen(buf) > 0 ? strlen(buf) : -1;
 	}
 
 	ACPI_FREE(obj);
 
-	return len;
+	return len > 0 ? len : -1;
 }
 
 static bool device_has_dsm(struct device *dev)
-- 
2.53.0