linux-kernel - [259/289] wmi: use memcmp instead of strncmp to compare GUIDs

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Date:	Tue, 07 Dec 2010 17:00:36 -0800
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Thadeu Lima de Souza Cascardo <cascardo@...oscopio.com>,
	Matthew Garrett <mjg@...hat.com>
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 <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>

---
 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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