2012-06-11 13:44:31

by Stephane Eranian

[permalink] [raw]
Subject: [PATCH] perf/x86: fix broken LBR fixup code


I noticed that the LBR fixups were not working anymore
on programs where they used to. I tracked this down to
a recent change to copy_from_user_nmi().

commit db0dc75d6403b6663c0eab4c6ccb672eb9b2ed72
Author: Arun Sharma <[email protected]>
Date: Fri Apr 20 15:41:36 2012 -0700

perf/x86: Check user address explicitly in copy_from_user_nmi()

This commit added a call to __range_not_ok() to the
copy_from_user_nmi() routine. The problem is that the logic
of the test must be reversed. __range_not_ok() returns 0 if the
range is VALID. We want to return early from copy_from_user_nmi()
if the range is NOT valid.

Signed-off-by: Stephane Eranian <[email protected]>
---

diff --git a/arch/x86/lib/usercopy.c b/arch/x86/lib/usercopy.c
index 677b1ed..4f74d94 100644
--- a/arch/x86/lib/usercopy.c
+++ b/arch/x86/lib/usercopy.c
@@ -22,7 +22,7 @@ copy_from_user_nmi(void *to, const void __user *from, unsigned long n)
void *map;
int ret;

- if (__range_not_ok(from, n, TASK_SIZE) == 0)
+ if (__range_not_ok(from, n, TASK_SIZE))
return len;

do {


2012-06-11 13:47:53

by Peter Zijlstra

[permalink] [raw]
Subject: Re: [PATCH] perf/x86: fix broken LBR fixup code

On Mon, 2012-06-11 at 15:44 +0200, Stephane Eranian wrote:
> I noticed that the LBR fixups were not working anymore
> on programs where they used to. I tracked this down to
> a recent change to copy_from_user_nmi().
>
> commit db0dc75d6403b6663c0eab4c6ccb672eb9b2ed72
> Author: Arun Sharma <[email protected]>
> Date: Fri Apr 20 15:41:36 2012 -0700
>
> perf/x86: Check user address explicitly in copy_from_user_nmi()
>
> This commit added a call to __range_not_ok() to the
> copy_from_user_nmi() routine. The problem is that the logic
> of the test must be reversed. __range_not_ok() returns 0 if the
> range is VALID. We want to return early from copy_from_user_nmi()
> if the range is NOT valid.

D'0h.. Thanks!

2012-06-11 19:41:17

by Arun Sharma

[permalink] [raw]
Subject: Re: [PATCH] perf/x86: fix broken LBR fixup code

On 6/11/12 6:47 AM, Peter Zijlstra wrote:
> On Mon, 2012-06-11 at 15:44 +0200, Stephane Eranian wrote:
>> I noticed that the LBR fixups were not working anymore
>> on programs where they used to. I tracked this down to
>> a recent change to copy_from_user_nmi().
>>
>> commit db0dc75d6403b6663c0eab4c6ccb672eb9b2ed72
>> Author: Arun Sharma<[email protected]>
>> Date: Fri Apr 20 15:41:36 2012 -0700
>>
>> perf/x86: Check user address explicitly in copy_from_user_nmi()
>>
>> This commit added a call to __range_not_ok() to the
>> copy_from_user_nmi() routine. The problem is that the logic
>> of the test must be reversed. __range_not_ok() returns 0 if the
>> range is VALID. We want to return early from copy_from_user_nmi()
>> if the range is NOT valid.
>
> D'0h.. Thanks!

My bad. I was fooled by all the kernel addresses that were unwound
properly. Didn't notice the broken unwinding in user space before I sent
the patch. The fix looks good. Thanks.

-Arun

2012-06-14 08:40:35

by Stephane Eranian

[permalink] [raw]
Subject: [tip:perf/urgent] perf/x86: Fix broken LBR fixup code

Commit-ID: 25f42985825dd93f0593efe454e54c2aa13f7830
Gitweb: http://git.kernel.org/tip/25f42985825dd93f0593efe454e54c2aa13f7830
Author: Stephane Eranian <[email protected]>
AuthorDate: Mon, 11 Jun 2012 15:44:26 +0200
Committer: Ingo Molnar <[email protected]>
CommitDate: Wed, 13 Jun 2012 15:00:28 +0200

perf/x86: Fix broken LBR fixup code

I noticed that the LBR fixups were not working anymore
on programs where they used to. I tracked this down to
a recent change to copy_from_user_nmi():

db0dc75d640 ("perf/x86: Check user address explicitly in copy_from_user_nmi()")

This commit added a call to __range_not_ok() to the
copy_from_user_nmi() routine. The problem is that the logic
of the test must be reversed. __range_not_ok() returns 0 if the
range is VALID. We want to return early from copy_from_user_nmi()
if the range is NOT valid.

Signed-off-by: Stephane Eranian <[email protected]>
Signed-off-by: Peter Zijlstra <[email protected]>
Acked-by: Arun Sharma <[email protected]>
Link: http://lkml.kernel.org/r/20120611134426.GA7542@quad
Signed-off-by: Ingo Molnar <[email protected]>
---
arch/x86/lib/usercopy.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/arch/x86/lib/usercopy.c b/arch/x86/lib/usercopy.c
index 677b1ed..4f74d94 100644
--- a/arch/x86/lib/usercopy.c
+++ b/arch/x86/lib/usercopy.c
@@ -22,7 +22,7 @@ copy_from_user_nmi(void *to, const void __user *from, unsigned long n)
void *map;
int ret;

- if (__range_not_ok(from, n, TASK_SIZE) == 0)
+ if (__range_not_ok(from, n, TASK_SIZE))
return len;

do {