2013-06-06 09:02:12

by Stephane Eranian

Subject: [PATCH] perf: fix hypervisor branch sampling permission check

Commit 2b923c8 perf/x86: Check branch sampling priv level in generic code
was missing the check for the hypervisor (HV) priv level, so add it back.

With this patch, we get the following correct behavior:

# echo 2 >/proc/sys/kernel/perf_event_paranoid

$ perf record -j any,k noploop 1
Error:
You may not have permission to collect stats.
Consider tweaking /proc/sys/kernel/perf_event_paranoid:
-1 - Not paranoid at all
0 - Disallow raw tracepoint access for unpriv
1 - Disallow cpu events for unpriv
2 - Disallow kernel profiling for unpriv

$ perf record -j any,hv noploop 1
Error:
You may not have permission to collect stats.
Consider tweaking /proc/sys/kernel/perf_event_paranoid:
-1 - Not paranoid at all
0 - Disallow raw tracepoint access for unpriv
1 - Disallow cpu events for unpriv
2 - Disallow kernel profiling for unpriv

Signed-off-by: Stephane Eranian <[email protected]>
---
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 95edd5a..f0880fb 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -6501,8 +6501,8 @@ static int perf_copy_attr(struct perf_event_attr __user *uattr,
*/
attr->branch_sample_type = mask;
}
- /* kernel level capture: check permissions */
- if ((mask & PERF_SAMPLE_BRANCH_KERNEL)
+ /* privileged levels capture (kernel, hv): check permissions */
+ if ((mask & PERF_SAMPLE_BRANCH_PERM_PLM)
&& perf_paranoid_kernel() && !capable(CAP_SYS_ADMIN))
return -EACCES;
}

2013-06-06 09:13:09

by Petr Matousek

Subject: Re: [PATCH] perf: fix hypervisor branch sampling permission check

On Thu, Jun 06, 2013 at 11:02:04AM +0200, Stephane Eranian wrote:
>
> Commit 2b923c8 perf/x86: Check branch sampling priv level in generic code
> was missing the check for the hypervisor (HV) priv level, so add it back.
>
> With this patch, we get the following correct behavior:
>
> # echo 2 >/proc/sys/kernel/perf_event_paranoid
>
> $ perf record -j any,k noploop 1
> Error:
> You may not have permission to collect stats.
> Consider tweaking /proc/sys/kernel/perf_event_paranoid:
> -1 - Not paranoid at all
> 0 - Disallow raw tracepoint access for unpriv
> 1 - Disallow cpu events for unpriv
> 2 - Disallow kernel profiling for unpriv
>
> $ perf record -j any,hv noploop 1
> Error:
> You may not have permission to collect stats.
> Consider tweaking /proc/sys/kernel/perf_event_paranoid:
> -1 - Not paranoid at all
> 0 - Disallow raw tracepoint access for unpriv
> 1 - Disallow cpu events for unpriv
> 2 - Disallow kernel profiling for unpriv
>
> Signed-off-by: Stephane Eranian <[email protected]>
> ---
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 95edd5a..f0880fb 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -6501,8 +6501,8 @@ static int perf_copy_attr(struct perf_event_attr __user *uattr,
> */
> attr->branch_sample_type = mask;
> }
> - /* kernel level capture: check permissions */
> - if ((mask & PERF_SAMPLE_BRANCH_KERNEL)
> + /* privileged levels capture (kernel, hv): check permissions */
> + if ((mask & PERF_SAMPLE_BRANCH_PERM_PLM)
> && perf_paranoid_kernel() && !capable(CAP_SYS_ADMIN))
> return -EACCES;
> }

Acked-by: Petr Matousek <[email protected]>

--
Petr Matousek / Red Hat Security Response Team

2013-06-19 18:39:15

by tip-bot for Vasyl Gomonovych

Subject: [tip:perf/core] perf: Fix hypervisor branch sampling permission check

Commit-ID: e712209a9e0b70e78b13847738eb66fe37412515
Gitweb: http://git.kernel.org/tip/e712209a9e0b70e78b13847738eb66fe37412515
Author: Stephane Eranian <[email protected]>
AuthorDate: Thu, 6 Jun 2013 11:02:04 +0200
Committer: Ingo Molnar <[email protected]>
CommitDate: Wed, 19 Jun 2013 12:50:21 +0200

perf: Fix hypervisor branch sampling permission check

Commit 2b923c8 perf/x86: Check branch sampling priv level in generic code
was missing the check for the hypervisor (HV) priv level, so add it back.

With this patch, we get the following correct behavior:

# echo 2 >/proc/sys/kernel/perf_event_paranoid

$ perf record -j any,k noploop 1
Error:
You may not have permission to collect stats.
Consider tweaking /proc/sys/kernel/perf_event_paranoid:
-1 - Not paranoid at all
0 - Disallow raw tracepoint access for unpriv
1 - Disallow cpu events for unpriv
2 - Disallow kernel profiling for unpriv

$ perf record -j any,hv noploop 1
Error:
You may not have permission to collect stats.
Consider tweaking /proc/sys/kernel/perf_event_paranoid:
-1 - Not paranoid at all
0 - Disallow raw tracepoint access for unpriv
1 - Disallow cpu events for unpriv
2 - Disallow kernel profiling for unpriv

Signed-off-by: Stephane Eranian <[email protected]>
Acked-by: Petr Matousek <[email protected]>
Signed-off-by: Peter Zijlstra <[email protected]>
Link: http://lkml.kernel.org/r/20130606090204.GA3725@quad
Signed-off-by: Ingo Molnar <[email protected]>
---
kernel/events/core.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index d0e0d0d..aca95bc 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -6573,8 +6573,8 @@ static int perf_copy_attr(struct perf_event_attr __user *uattr,
*/
attr->branch_sample_type = mask;
}
- /* kernel level capture: check permissions */
- if ((mask & PERF_SAMPLE_BRANCH_KERNEL)
+ /* privileged levels capture (kernel, hv): check permissions */
+ if ((mask & PERF_SAMPLE_BRANCH_PERM_PLM)
&& perf_paranoid_kernel() && !capable(CAP_SYS_ADMIN))
return -EACCES;
}