From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 41233C624D7 for ; Wed, 2 Sep 2026 14:24:10 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 031B410F22C; Wed, 2 Sep 2026 14:24:10 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=intel.com header.i=@intel.com header.b="bDDLTJzz"; dkim-atps=neutral Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.20]) by gabe.freedesktop.org (Postfix) with ESMTPS id E9B0E10F20F; Wed, 2 Sep 2026 14:24:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1788359049; x=1819895049; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=E3ZXddGQvDMVMDCZVUnrJk1V0CUpaHzJBFjF2HOHxO8=; b=bDDLTJzzAJIqT0G6mLK4MtAhJBeGdtjZToVbIuEySmJW6v3634e5t0Og iVA0W4xvT0wu178ZsNdNlBJ4UbdcKKxUoRFPWa03G5W7BwmL6zE3Hk3E4 IPHpc6qUgqgF+KdvmjIjKl/HBNUP7p11eMHwtZqHJGOiP1pARlDNBQJ+Y RCncIHssTZMVhiZpUynLDEi9Amd/LnJ/4m+pvb27o76/s53MaEZGZdW9G p670EhxDqP1cXtQXZ/scMNLBGFPwmRI7V3sPGZW4TVUtYuiqWibUW5zfZ cAHWU5PkM8Ybxa+qZ0rf4yex+IAZ4v7MLz265wlTcdKYSZfmeJLLT0uqw A==; X-CSE-ConnectionGUID: d5gXe7RrQMKW8tzguiWymg== X-CSE-MsgGUID: 412/rcttReG79s28C4DTPg== X-IronPort-AV: E=McAfee;i="6800,10657,11894"; a="88581617" X-IronPort-AV: E=Sophos;i="6.25,258,1779174000"; d="scan'208";a="88581617" Received: from fmviesa007.fm.intel.com ([10.60.135.147]) by orvoesa112.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Sep 2026 07:24:08 -0700 X-CSE-ConnectionGUID: +B5XVXg0R8Ct85wSP/jtiA== X-CSE-MsgGUID: kRokep9tSgib9nJOSDCvaw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.25,258,1779174000"; d="scan'208";a="266186410" Received: from vbelgaum-ubuntu.fm.intel.com ([10.1.39.16]) by fmviesa007.fm.intel.com with ESMTP; 02 Sep 2026 07:24:08 -0700 From: Vinay Belgaumkar To: intel-xe@lists.freedesktop.org Cc: dri-devel@lists.freedesktop.org, Vinay Belgaumkar , Alexander Kanevskiy , Dapeng Mi Subject: [PATCH v6 1/2] perf: Fix null pointer access in is_include_guest_event() Date: Wed, 2 Sep 2026 07:18:23 -0700 Message-Id: <20260902141824.733112-2-vinay.belgaumkar@intel.com> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20260902141824.733112-1-vinay.belgaumkar@intel.com> References: <20260902141824.733112-1-vinay.belgaumkar@intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-BeenThere: intel-xe@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel Xe graphics driver List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-xe-bounces@lists.freedesktop.org Sender: "Intel-xe" A typical module unload occurring event when there is an active perf connection leads to freeing of the pmu pointer. The call log is something like: .. __pmu_detach_event pmu_detach_event pmu_detach_events perf_pmu_unregister .. __pmu_detach_event() sets event->pmu to null. When the perf connection finally is closed, the following stack trace is observed: Oops: general protection fault, kernel NULL pointer dereference ... RIP: 0010:_free_event+0x3e/0x370 ... Call Trace: ... perf_event_release_kernel+0x260/0x2d0 perf_release+0x12/0x20 A call to mediated_pmu_unaccount_event() inside _free_event() is the root cause of this crash. Adding a check inside is_include_guest_event() ensures we don't accidentally access a null pmu ptr. In addition to this, we will now call mediated_pmu_unaccount_event() before clearing the pmu ptr so that nr_include_guest_events counts are maintained correctly. v2: Add another check to prevent null access (sashiko) v3: Use READ_ONCE for checking pmu state (sashiko) v4: READ_ONCE for the pmu check as well (sashiko) v5: Improve commit message and split patch into 2 (Dapeng) Fixes: eff95e170275 ("perf: Add APIs to create/release mediated guest vPMUs") Cc: Alexander Kanevskiy Cc: Dapeng Mi Assisted-by: Claude:Claude-Sonnet-5 Signed-off-by: Vinay Belgaumkar --- kernel/events/core.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/kernel/events/core.c b/kernel/events/core.c index 94ca277e0819..f19d27ac411d 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -6350,6 +6350,9 @@ static DEFINE_MUTEX(perf_mediated_pmu_mutex); /* !exclude_guest event of PMU with PERF_PMU_CAP_MEDIATED_VPMU */ static inline bool is_include_guest_event(struct perf_event *event) { + if (!event->pmu) + return false; + if ((event->pmu->capabilities & PERF_PMU_CAP_MEDIATED_VPMU) && !event->attr.exclude_guest) return true; @@ -12977,6 +12980,7 @@ static void __pmu_detach_event(struct pmu *pmu, struct perf_event *event, exclusive_event_destroy(event); module_put(pmu->module); + mediated_pmu_unaccount_event(event); event->pmu = NULL; /* force fault instead of UAF */ } -- 2.38.1