linux-kernel - [PATCH v2] i915/perf: Fix NULL deref bugs with drm

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Date:   Fri, 27 Oct 2023 10:28:22 -0700
From:   Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>
To:     Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Andrzej Hajda <andrzej.hajda@...el.com>,
        Umesh Nerlige Ramappa <umesh.nerlige.ramappa@...el.com>,
        Matt Roper <matthew.d.roper@...el.com>,
        Lionel Landwerlin <lionel.g.landwerlin@...el.com>,
        intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Cc:     dan.carpenter@...aro.org, kernel-janitors@...r.kernel.org,
        error27@...il.com, harshit.m.mogalapalli@...cle.com,
        Tvrtko Ursulin <tvrtko.ursulin@...el.com>
Subject: [PATCH v2] i915/perf: Fix NULL deref bugs with drm_dbg() calls

When i915 perf interface is not available dereferencing it will lead to
NULL dereferences.

As returning -ENOTSUPP is pretty clear return when perf interface is not
available.

Fixes: 2fec539112e8 ("i915/perf: Replace DRM_DEBUG with driver specific drm_dbg call")
Suggested-by: Tvrtko Ursulin <tvrtko.ursulin@...el.com>
Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>
---
v1 --> v2: Remove the debug calls as they don't add much value and
-ENOTSUPP is a good enough return value.
---
 drivers/gpu/drm/i915/i915_perf.c | 15 +++------------
 1 file changed, 3 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_perf.c b/drivers/gpu/drm/i915/i915_perf.c
index 2f3ecd7d4804..7b1c8de2f9cb 100644
--- a/drivers/gpu/drm/i915/i915_perf.c
+++ b/drivers/gpu/drm/i915/i915_perf.c
@@ -4227,11 +4227,8 @@ int i915_perf_open_ioctl(struct drm_device *dev, void *data,
 	u32 known_open_flags;
 	int ret;
 
-	if (!perf->i915) {
-		drm_dbg(&perf->i915->drm,
-			"i915 perf interface not available for this system\n");
+	if (!perf->i915)
 		return -ENOTSUPP;
-	}
 
 	known_open_flags = I915_PERF_FLAG_FD_CLOEXEC |
 			   I915_PERF_FLAG_FD_NONBLOCK |
@@ -4607,11 +4604,8 @@ int i915_perf_add_config_ioctl(struct drm_device *dev, void *data,
 	struct i915_oa_reg *regs;
 	int err, id;
 
-	if (!perf->i915) {
-		drm_dbg(&perf->i915->drm,
-			"i915 perf interface not available for this system\n");
+	if (!perf->i915)
 		return -ENOTSUPP;
-	}
 
 	if (!perf->metrics_kobj) {
 		drm_dbg(&perf->i915->drm,
@@ -4773,11 +4767,8 @@ int i915_perf_remove_config_ioctl(struct drm_device *dev, void *data,
 	struct i915_oa_config *oa_config;
 	int ret;
 
-	if (!perf->i915) {
-		drm_dbg(&perf->i915->drm,
-			"i915 perf interface not available for this system\n");
+	if (!perf->i915)
 		return -ENOTSUPP;
-	}
 
 	if (i915_perf_stream_paranoid && !perfmon_capable()) {
 		drm_dbg(&perf->i915->drm,
-- 
2.39.3