Home page logo
/

oss-sec logo oss-sec mailing list archives

Re: [PATCH] perf: fix hypervisor branch sampling permission check
From: Petr Matousek <pmatouse () redhat com>
Date: Thu, 6 Jun 2013 11:12:06 +0200

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


  By Date           By Thread  

Current thread:
[ Nmap | Sec Tools | Mailing Lists | Site News | About/Contact | Advertising | Privacy ]
AlienVault