linux-kernel - [PATCH v2 4/7] drm/i915/perf: open access for CAP_SYS

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Date:   Mon, 16 Dec 2019 10:17:07 +0300
From:   Alexey Budankov <alexey.budankov@...ux.intel.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Ingo Molnar <mingo@...hat.com>, jani.nikula@...ux.intel.com,
        joonas.lahtinen@...ux.intel.com, rodrigo.vivi@...el.com,
        Alexei Starovoitov <ast@...nel.org>,
        james.bottomley@...senpartnership.com, benh@...nel.crashing.org,
        Casey Schaufler <casey@...aufler-ca.com>, serge@...lyn.com,
        James Morris <jmorris@...ei.org>
Cc:     Jiri Olsa <jolsa@...hat.com>, Andi Kleen <ak@...ux.intel.com>,
        Stephane Eranian <eranian@...gle.com>,
        Igor Lubashev <ilubashe@...mai.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Jann Horn <jannh@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
        linux-security-module@...r.kernel.org, selinux@...r.kernel.org,
        linux-kernel <linux-kernel@...r.kernel.org>,
        "linux-perf-users@...r.kernel.org" <linux-perf-users@...r.kernel.org>,
        intel-gfx@...ts.freedesktop.org, bgregg@...flix.com,
        Song Liu <songliubraving@...com>, bpf@...r.kernel.org,
        linux-parisc@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH v2 4/7] drm/i915/perf: open access for CAP_SYS_PERFMON
 privileged process


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@...ux.intel.com>
---
 drivers/gpu/drm/i915/i915_perf.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_perf.c b/drivers/gpu/drm/i915/i915_perf.c
index e42b86827d6b..8a9ff40b1b0b 100644
--- a/drivers/gpu/drm/i915/i915_perf.c
+++ b/drivers/gpu/drm/i915/i915_perf.c
@@ -2748,10 +2748,11 @@ 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 &&
+	    !(capable(CAP_SYS_PERFMON) || capable(CAP_SYS_ADMIN))) {
 		DRM_DEBUG("Insufficient privileges to open system-wide i915 perf stream\n");
 		ret = -EACCES;
 		goto err_ctx;
@@ -2940,8 +2941,8 @@ static int read_properties_unlocked(struct drm_i915_private *dev_priv,
 				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",
+			    !(capable(CAP_SYS_PERFMON) || capable(CAP_SYS_ADMIN))) {
+				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 +3329,7 @@ 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 && !(capable(CAP_SYS_PERFMON) || capable(CAP_SYS_ADMIN))) {
 		DRM_DEBUG("Insufficient privileges to add i915 OA config\n");
 		return -EACCES;
 	}
@@ -3474,7 +3475,7 @@ 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 && !(capable(CAP_SYS_PERFMON) || capable(CAP_SYS_ADMIN))) {
 		DRM_DEBUG("Insufficient privileges to remove i915 OA config\n");
 		return -EACCES;
 	}
-- 
2.20.1