[PATCH 5.13 211/351] PCI/sysfs: Fix dsm_label_utf16s_to_utf8s() buffer overrun

[Greg Kroah-Hartman]

From: Krzysztof Wilczyński <kw@xxxxxxxxx>

[ Upstream commit bdcdaa13ad96f1a530711c29e6d4b8311eff767c ]

"utf16s_to_utf8s(..., buf, PAGE_SIZE)" puts up to PAGE_SIZE bytes into
"buf" and returns the number of bytes it actually put there.  If it wrote
PAGE_SIZE bytes, the newline added by dsm_label_utf16s_to_utf8s() would
overrun "buf".

Reduce the size available for utf16s_to_utf8s() to use so there is always
space for the newline.

[bhelgaas: reorder patch in series, commit log]
Fixes: 6058989bad05 ("PCI: Export ACPI _DSM provided firmware instance number and string name to sysfs")
Link: https://lore.kernel.org/r/20210603000112.703037-7-kw@xxxxxxxxx
Reported-by: Joe Perches <joe@xxxxxxxxxxx>
Signed-off-by: Krzysztof Wilczyński <kw@xxxxxxxxx>
Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/pci/pci-label.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/pci/pci-label.c b/drivers/pci/pci-label.c
index c32f3b7540e8..76b381cf70b2 100644
--- a/drivers/pci/pci-label.c
+++ b/drivers/pci/pci-label.c
@@ -145,7 +145,7 @@ static void dsm_label_utf16s_to_utf8s(union acpi_object *obj, char *buf)
 	len = utf16s_to_utf8s((const wchar_t *)obj->buffer.pointer,
 			      obj->buffer.length,
 			      UTF16_LITTLE_ENDIAN,
-			      buf, PAGE_SIZE);
+			      buf, PAGE_SIZE - 1);
 	buf[len] = '\n';
 }
 
-- 
2.30.2