[tip:perf/urgent] perf: Fix incorrect copy_from_user() usage

[tip-bot for John Blackwood <john.blackwood@ccur.com>]

Commit-ID:  ad0cf3478de8677f720ee06393b3147819568d6a
Gitweb:     http://git.kernel.org/tip/ad0cf3478de8677f720ee06393b3147819568d6a
Author:     John Blackwood <john.blackwood@ccur.com>
AuthorDate: Tue, 28 Sep 2010 18:03:11 -0400
Committer:  Ingo Molnar <mingo@elte.hu>
CommitDate: Tue, 12 Oct 2010 11:45:01 +0200

perf: Fix incorrect copy_from_user() usage

perf events: repair incorrect use of copy_from_user

This makes the perf_event_period() return 0 instead of
-EFAULT on success.

Signed-off-by: John Blackwood<john.blackwood@ccur.com>
Signed-off-by: Joe Korty <joe.korty@ccur.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20100928220311.GA18145@tsunami.ccur.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
 kernel/perf_event.c |    4 +---
 1 files changed, 1 insertions(+), 3 deletions(-)

diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index db5b560..b98bed3 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -2202,15 +2202,13 @@ static void perf_event_for_each(struct perf_event *event,
 static int perf_event_period(struct perf_event *event, u64 __user *arg)
 {
 	struct perf_event_context *ctx = event->ctx;
-	unsigned long size;
 	int ret = 0;
 	u64 value;
 
 	if (!event->attr.sample_period)
 		return -EINVAL;
 
-	size = copy_from_user(&value, arg, sizeof(value));
-	if (size != sizeof(value))
+	if (copy_from_user(&value, arg, sizeof(value)))
 		return -EFAULT;
 
 	if (!value)