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Subject[259/289] wmi: use memcmp instead of strncmp to compare GUIDs
2.6.36-stable review patch.  If anyone has any objections, please let us know.


From: Thadeu Lima de Souza Cascardo <>

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 <>
Signed-off-by: Matthew Garrett <>
Signed-off-by: Greg Kroah-Hartman <>

drivers/platform/x86/wmi.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/platform/x86/wmi.c
+++ b/drivers/platform/x86/wmi.c
@@ -801,7 +801,7 @@ static bool guid_already_parsed(const ch
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;

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