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

[Petr Matousek <pmatouse () redhat com>]

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 <eranian () google com>
> ---
> 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 <pmatouse () redhat com>

-- 
Petr Matousek / Red Hat Security Response Team