linux-kernel - [PATCH 02/10] x86, mce: mce_read can check args without mutex

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Date:	Mon, 05 Oct 2009 15:34:09 +0900
From:	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>
To:	Huang Ying <ying.huang@...el.com>
CC:	Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
	Andi Kleen <ak@...ux.intel.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: [PATCH 02/10] x86, mce: mce_read can check args without mutex

Move it before mutex_lock().

Signed-off-by: Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>
---
 arch/x86/kernel/cpu/mcheck/mce.c |   11 ++++-------
 1 files changed, 4 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index 28e1e14..2d0f9d8 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -1458,15 +1458,12 @@ static ssize_t mce_read(struct file *filp, char __user *ubuf, size_t usize,
 	unsigned prev, next;
 	int i, err;
 
-	mutex_lock(&mce_read_mutex);
-	next = rcu_dereference(mcelog.next);
-
 	/* Only supports full reads right now */
-	if (*off != 0 || usize < MCE_LOG_LEN*sizeof(struct mce)) {
-		mutex_unlock(&mce_read_mutex);
-
+	if (*off != 0 || usize < sizeof(struct mce) * MCE_LOG_LEN)
 		return -EINVAL;
-	}
+
+	mutex_lock(&mce_read_mutex);
+	next = rcu_dereference(mcelog.next);
 
 	err = 0;
 	prev = 0;
-- 
1.6.4.3


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