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

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Message-Id: <1290980810-5903-1-git-send-email-cascardo@holoscopio.com>
Date:	Sun, 28 Nov 2010 19:46:50 -0200
From:	Thadeu Lima de Souza Cascardo <cascardo@...oscopio.com>
To:	platform-driver-x86@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, mjg@...hat.com,
	carlos@...angeworlds.co.uk, stable@...nel.org, ceolin@...vel.com,
	Thadeu Lima de Souza Cascardo <cascardo@...oscopio.com>
Subject: [PATCH] wmi: use memcmp instead of strncmp to compare GUIDs

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>
---
 drivers/platform/x86/wmi.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/drivers/platform/x86/wmi.c b/drivers/platform/x86/wmi.c
index 104b77c..aecd9a9 100644
--- a/drivers/platform/x86/wmi.c
+++ b/drivers/platform/x86/wmi.c
@@ -755,7 +755,7 @@ static bool guid_already_parsed(const char *guid_string)
 	struct wmi_block *wblock;
 
 	list_for_each_entry(wblock, &wmi_block_list, list)
-		if (strncmp(wblock->gblock.guid, guid_string, 16) == 0)
+		if (memcmp(wblock->gblock.guid, guid_string, 16) == 0)
 			return true;
 
 	return false;
-- 
1.7.2.3

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