[v3,4/7] drm/i915/perf: open access for CAP_SYS_PERFMON privileged process

Commit Message

Alexey Budankov Dec. 16, 2019, 8:03 p.m. UTC

Open access to i915_perf monitoring for CAP_SYS_PERFMON privileged processes.
For backward compatibility reasons access to i915_perf subsystem remains open
for CAP_SYS_ADMIN privileged processes but CAP_SYS_ADMIN usage for secure
i915_perf monitoring is discouraged with respect to CAP_SYS_PERFMON capability.

Signed-off-by: Alexey Budankov <[e-mail]>
---
 drivers/gpu/drm/i915/i915_perf.c | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

Comments

Lionel Landwerlin Dec. 17, 2019, 9:45 a.m. UTC | #1

On 16/12/2019 22:03, Alexey Budankov wrote:
> Open access to i915_perf monitoring for CAP_SYS_PERFMON privileged processes.
> For backward compatibility reasons access to i915_perf subsystem remains open
> for CAP_SYS_ADMIN privileged processes but CAP_SYS_ADMIN usage for secure
> i915_perf monitoring is discouraged with respect to CAP_SYS_PERFMON capability.
>
> Signed-off-by: Alexey Budankov <[e-mail]>


Assuming people are fine with this new cap, I like this idea of a 
lighter privilege for i915-perf.


-Lionel

Alexey Budankov Dec. 17, 2019, 11:38 a.m. UTC | #2

On 17.12.2019 12:45, Lionel Landwerlin wrote:
> On 16/12/2019 22:03, Alexey Budankov wrote:
>> Open access to i915_perf monitoring for CAP_SYS_PERFMON privileged processes.
>> For backward compatibility reasons access to i915_perf subsystem remains open
>> for CAP_SYS_ADMIN privileged processes but CAP_SYS_ADMIN usage for secure
>> i915_perf monitoring is discouraged with respect to CAP_SYS_PERFMON capability.
>>
>> Signed-off-by: Alexey Budankov <[e-mail]>
> 
> 
> Assuming people are fine with this new cap, I like this idea of a lighter privilege for i915-perf.

Lionel, thanks for your meaningful input!
Appreciate your collaboration.

Regards,
Alexey

> 
> 
> -Lionel
> 
> 
>

Patch

diff --git a/drivers/gpu/drm/i915/i915_perf.c b/drivers/gpu/drm/i915/i915_perf.c
index e42b86827d6b..e2697f8d04de 100644
--- a/drivers/gpu/drm/i915/i915_perf.c
+++ b/drivers/gpu/drm/i915/i915_perf.c
@@ -2748,10 +2748,10 @@  i915_perf_open_ioctl_locked(struct drm_i915_private *dev_priv,
 	/* Similar to perf's kernel.perf_paranoid_cpu sysctl option
 	 * we check a dev.i915.perf_stream_paranoid sysctl option
 	 * to determine if it's ok to access system wide OA counters
-	 * without CAP_SYS_ADMIN privileges.
+	 * without CAP_SYS_PERFMON or CAP_SYS_ADMIN privileges.
 	 */
 	if (privileged_op &&
-	    i915_perf_stream_paranoid && !capable(CAP_SYS_ADMIN)) {
+	    i915_perf_stream_paranoid && !perfmon_capable()) {
 		DRM_DEBUG("Insufficient privileges to open system-wide i915 perf stream\n");
 		ret = -EACCES;
 		goto err_ctx;
@@ -2939,9 +2939,8 @@  static int read_properties_unlocked(struct drm_i915_private *dev_priv,
 			} else
 				oa_freq_hz = 0;
 
-			if (oa_freq_hz > i915_oa_max_sample_rate &&
-			    !capable(CAP_SYS_ADMIN)) {
-				DRM_DEBUG("OA exponent would exceed the max sampling frequency (sysctl dev.i915.oa_max_sample_rate) %uHz without root privileges\n",
+			if (oa_freq_hz > i915_oa_max_sample_rate && !perfmon_capable()) {
+				DRM_DEBUG("OA exponent would exceed the max sampling frequency (sysctl dev.i915.oa_max_sample_rate) %uHz without CAP_SYS_PERFMON or CAP_SYS_ADMIN privileges\n",
 					  i915_oa_max_sample_rate);
 				return -EACCES;
 			}
@@ -3328,7 +3327,7 @@  int i915_perf_add_config_ioctl(struct drm_device *dev, void *data,
 		return -EINVAL;
 	}
 
-	if (i915_perf_stream_paranoid && !capable(CAP_SYS_ADMIN)) {
+	if (i915_perf_stream_paranoid && !perfmon_capable()) {
 		DRM_DEBUG("Insufficient privileges to add i915 OA config\n");
 		return -EACCES;
 	}
@@ -3474,7 +3473,7 @@  int i915_perf_remove_config_ioctl(struct drm_device *dev, void *data,
 		return -ENOTSUPP;
 	}
 
-	if (i915_perf_stream_paranoid && !capable(CAP_SYS_ADMIN)) {
+	if (i915_perf_stream_paranoid && !perfmon_capable()) {
 		DRM_DEBUG("Insufficient privileges to remove i915 OA config\n");
 		return -EACCES;
 	}