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 67773C61DFD for ; Mon, 31 Aug 2026 21:57:53 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id E61AC10E121; Mon, 31 Aug 2026 21:57:52 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=intel.com header.i=@intel.com header.b="RhJC+ylv"; dkim-atps=neutral Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.17]) by gabe.freedesktop.org (Postfix) with ESMTPS id 9C43A10E121; Mon, 31 Aug 2026 21:57:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1788213471; x=1819749471; h=from:to:cc:subject:date:message-id:mime-version: content-transfer-encoding; bh=1yzhN672F5qDXh1gYKhfULSneIovWsGKg3ZHs7CEAbY=; b=RhJC+ylv/mMYBwleMdkispIooeM4N8w8506L3YO1BJy3xQ6r0OZpSeQO i31d8wxu1eB8AsMimZshCOqkd43HKqsZMDKqHqBrEMTEPdzLRW7VfrvEK Ny9RlE1Lw+OdL/pX6SFtOnW7ZankZ+NLT2lc5IwSNSMm7XSWDnv50Q2nU +aruoMgFRbaqvbD3q8rDTvlMRqyPm7CLgskpkW/QNCQkCYUgHHqpqSE9R Hq4QPetkxYxwYv7rF7u2/A0KXU249ht4wN+ZJy6Sh2GW2KarZwLawisor cdqezRYzsigXsS+cm/2V6UKdNeRzz5K1k42/5Tfjyw1HtVfcdVUJKJgN5 g==; X-CSE-ConnectionGUID: b4d7ZHOGQbOQg2GjYc0MNQ== X-CSE-MsgGUID: 4XF5OCd3RMenOwu2hQbXDg== X-IronPort-AV: E=McAfee;i="6800,10657,11892"; a="88507176" X-IronPort-AV: E=Sophos;i="6.25,254,1779174000"; d="scan'208";a="88507176" Received: from fmviesa003.fm.intel.com ([10.60.135.143]) by fmvoesa111.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 31 Aug 2026 14:57:51 -0700 X-CSE-ConnectionGUID: 4l7hzdwWQzyGZ0W9b1N2RQ== X-CSE-MsgGUID: nNQLeoCLTYaTt56YhIpPHg== X-ExtLoop1: 1 Received: from vbelgaum-ubuntu.fm.intel.com ([10.1.39.16]) by fmviesa003.fm.intel.com with ESMTP; 31 Aug 2026 14:57:51 -0700 From: Vinay Belgaumkar To: intel-xe@lists.freedesktop.org Cc: dri-devel@lists.freedesktop.org, Vinay Belgaumkar , Alexander Kanevskiy , Dapeng Mi Subject: [PATCH v3] perf: Fix null pointer access in is_include_guest_event() Date: Mon, 31 Aug 2026 14:52:14 -0700 Message-Id: <20260831215214.4169965-1-vinay.belgaumkar@intel.com> X-Mailer: git-send-email 2.38.1 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 kernel panic is observed when an application has a perf connection open and the driver managing the pmu event unbinds. The issue occurs when perf_pmu_unregister() is called while there is an active perf session. The null pointer error is seen when the event is freed through __free_event() and mediated_pmu_unaccount_event is called. There is a missing null check inside is_include_guest_event(). Also call mediated_pmu_unaccount_event() inside __pmu_detach_event() similar to __free_event(). Signature of the failure: 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 While here, also add a null check inside perf_event_read_local() which can cause a similar crash. Sashiko pointed out a possible race between when we check for revoked state here and then actually access event-pmu inside __perf_event_read_cpu(). So, add another null check there. v2: Add another check to prevent null access (sashiko) v3: Use READ_ONCE for checking pmu state (sashiko) 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 | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/kernel/events/core.c b/kernel/events/core.c index 94ca277e0819..6ca464f10ba8 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -4794,6 +4794,9 @@ static int __perf_event_read_cpu(struct perf_event *event, int event_cpu) if ((unsigned)event_cpu >= nr_cpu_ids) return event_cpu; + if (!event->pmu) + return -ENODEV; + if (event->group_caps & PERF_EV_CAP_READ_SCOPE) { const struct cpumask *cpumask = perf_scope_cpu_topology_cpumask(event->pmu->scope, event_cpu); @@ -4917,6 +4920,11 @@ int perf_event_read_local(struct perf_event *event, u64 *value, goto out; } + if (READ_ONCE(event->state) <= PERF_EVENT_STATE_REVOKED) { + ret = -ENODEV; + goto out; + } + /* * Get the event CPU numbers, and adjust them to local if the event is * a per-package event that can be read locally @@ -6350,6 +6358,9 @@ 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 +12988,7 @@ 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