wmi: use memcmp instead of strncmp to compare GUIDs

commit 8b14d7b22c61f17ccb869e0047d9df6dd9f50a9f upstream.

While looking for the duplicates in /sys/class/wmi/, I couldn't find
them. The code that looks for duplicates uses strncmp in a binary GUID,
which may contain zero bytes. The right function is memcmp, which is
also used in another section of wmi code.

It was finding 49142400-C6A3-40FA-BADB-8A2652834100 as a duplicate of
39142400-C6A3-40FA-BADB-8A2652834100. Since the first byte is the fourth
printed, they were found as equal by strncmp.

Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@holoscopio.com>
Signed-off-by: Matthew Garrett <mjg@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/platform/x86/wmi.c b/drivers/platform/x86/wmi.c
index b104302fea0a1e9dbc4a91f82290a185ad244e00..a82f18ec8e4c94223bd3b9813be241bc581b7597 100644 (file)
--- a/drivers/platform/x86/wmi.c
+++ b/drivers/platform/x86/wmi.c
@@ -724,7 +724,7 @@ static bool guid_already_parsed(const char *guid_string)
                wblock = list_entry(p, struct wmi_block, list);
                gblock = &wblock->gblock;
 
-               if (strncmp(gblock->guid, guid_string, 16) == 0)
+               if (memcmp(gblock->guid, guid_string, 16) == 0)
                        return true;
        }
        return false;