From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.6]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 06C6433A6E2; Fri, 18 Sep 2026 01:07:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.6 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789693639; cv=none; b=P3L6f7gWD0nSmjpKOy6ZryyJg6xv5g3KwO7/qGTjIIJT6K8Yy17yFF9NNebUuV0SQykqBECGnHop/8HOkAXdKgfLCwShdUWoqg2HZ41xvXTWN41u/wcpWYl7Fc2QSMNwr8KVAu2IyvJckRXFhyo1jAyFpruNXHBdEilgHZGtQHk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789693639; c=relaxed/simple; bh=jEy1qsPKGpZ3QCoInn+hoo5zhrDBOFfC/hMzI3kUBRo=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=RQKPZssPx/omLgRl2wmg9+fyQL7Hzlhi1bAv3ViLtPeTgTZr+n3+/jE2qyVTj7HgVuwYVXx3G91C3t+loq1P5ftH39HhywjcsaOwP57GG3wLsocFPSDM8LMDJVyK2FgM6lcq5Ir3hjklgMQ4Rhquq8RN/y4pCw5SdJnNUoCu7rA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=pass smtp.mailfrom=linux.intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=NG6/LZ0f; arc=none smtp.client-ip=192.198.163.6 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="NG6/LZ0f" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1789693638; x=1821229638; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=jEy1qsPKGpZ3QCoInn+hoo5zhrDBOFfC/hMzI3kUBRo=; b=NG6/LZ0f4iTd/8DTaXjRKKcsOgvtUVqgpApFkNC8cYPo8+21DdzBTS6/ 6mwAdtVM67CSWb+AM847ZZ99Tyub27+8VQidywLoRTTUHQ9+KtYUSmlaZ AHE2HFUNcsTbXL8xfCli8zZvns+PWpPm0OdU8ulRVMciFu6LEQZpRLxcK /19tUMNNWFRAXD+R2hM+zZ5fY19BiykLeULopJBMH6rxE4yVICfN8Jf99 PTXB5O++AKlxw0WxpqPN94jefVRJFUdYBp+iMo8CjiSzqTN+g22Dlc6k7 cKoAXyttQs0Mgz7k0mDxKtGzFzwN1WUk6JZ1GIKXJicV61Z3s5J9lceF7 A==; X-CSE-ConnectionGUID: TK+sV2JVQzqDDH3VhIqslA== X-CSE-MsgGUID: wgdp4s/kR8qAFVgYQcD/YA== X-IronPort-AV: E=McAfee;i="6800,10657,11905"; a="686641" X-IronPort-AV: E=Sophos;i="6.27,103,1787036400"; d="scan'208";a="686641" Received: from fmviesa006.fm.intel.com ([10.60.135.146]) by fmvoesa116.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Sep 2026 18:07:17 -0700 X-CSE-ConnectionGUID: tDanl5A8QESGzcV9CZFbgw== X-CSE-MsgGUID: 1nE6uy8aR1agCFq2vQTZ/Q== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.27,103,1787036400"; d="scan'208";a="269834914" Received: from dapengmi-mobl1.ccr.corp.intel.com (HELO [10.124.241.239]) ([10.124.241.239]) by fmviesa006-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Sep 2026 18:07:13 -0700 Message-ID: Date: Fri, 18 Sep 2026 09:07:11 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/2] perf: Fix null pointer access in is_include_guest_event() To: Vinay Belgaumkar , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Namhyung Kim , Ian Rogers , Adrian Hunter , Alexander Shishkin , Andi Kleen , Eranian Stephane Cc: linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, Alexander Kanevskiy References: <20260904181625.1394082-1-vinay.belgaumkar@intel.com> Content-Language: en-US From: "Mi, Dapeng" In-Reply-To: <20260904181625.1394082-1-vinay.belgaumkar@intel.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Better update the prefix of short log to "perf/core:", other looks good to me. Thanks. Reviewed-by: Dapeng Mi On 9/5/2026 2:16 AM, Vinay Belgaumkar wrote: > 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. > > 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 a6c8e38a3110..7777e82aad5e 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; > @@ -13002,6 +13005,7 @@ 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 */ > } >