Re: [PATCH v4 4/9] drm/i915/perf: open access for CAP_SYS_PERFMON privileged process

[Lionel Landwerlin]

On 18/12/2019 11:27, 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 <alexey.budankov@xxxxxxxxxxxxxxx>

Acked-by: Lionel Landwerlin <lionel.g.landwerlin@xxxxxxxxx>

> ---
>   drivers/gpu/drm/i915/i915_perf.c | 13 ++++++-------
>   1 file changed, 6 insertions(+), 7 deletions(-)
>
> 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;
>   	}