linux-kernel - [PATCH] [196/223] wmi: use memcmp instead of strncmp to compare GUIDs

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Date:	Mon, 13 Dec 2010 00:48:22 +0100 (CET)
From:	Andi Kleen <andi@...stfloor.org>
To:	cascardo@...oscopio.com, mjg@...hat.com, gregkh@...e.de,
	ak@...ux.intel.com, linux-kernel@...r.kernel.org, stable@...nel.org
Subject: [PATCH] [196/223] wmi: use memcmp instead of strncmp to compare GUIDs

2.6.35-longterm review patch.  If anyone has any objections, please let me know.

------------------
From: Thadeu Lima de Souza Cascardo <cascardo@...oscopio.com>

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@...oscopio.com>
Signed-off-by: Matthew Garrett <mjg@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>
Signed-off-by: Andi Kleen <ak@...ux.intel.com>

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

Index: linux/drivers/platform/x86/wmi.c
===================================================================
--- linux.orig/drivers/platform/x86/wmi.c
+++ linux/drivers/platform/x86/wmi.c
@@ -795,7 +795,7 @@ 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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