From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.21]) (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 10E413A7193; Mon, 7 Sep 2026 06:24:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.21 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788762302; cv=none; b=mtGpH8GVaCzhIWKayeyHF5j6AWKBPtpVzm/eeCftuU60yuKSxN/GAdqyrwEET+8bYG79cepF/lDWZW7K8inpaULCJk7+5MPtJSfQxaR9TfCZVpneu7AcOP3GQv2Jbwwqt42hFnf4W0yqMmKcI20olJv2COeFify6xJJ8ULV9yBI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788762302; c=relaxed/simple; bh=CmxHwiGY44Ct/DwK/K2mbNhd/0rIQlcqBYb/wuafWwk=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=VCSADn8Rd1t6+TRQmpOrs1yi+1x1AKhKR8rgG2Lt6I2xo/9aINMSpH7X1ZERixe2LOOUyeLpYWOVQw49Cl3ytxk7UZLaknk0cxZ44On78mGdOPbXhWD2vwlJUizu/+QXWMu6JawEP8jK/rVyniCpGnGp+DiW2MUbi5SPNVN1yVQ= 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=KNaYLp8s; arc=none smtp.client-ip=198.175.65.21 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="KNaYLp8s" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1788762297; x=1820298297; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=CmxHwiGY44Ct/DwK/K2mbNhd/0rIQlcqBYb/wuafWwk=; b=KNaYLp8s1sfZ942pDkH9/UTxX4EM1eUBS7LN4IjSm7B4MpD3LqPvPiuv UyQNrFWK8bpjLKTwDLxga7hPQV/bosQw+/7UXjjDc+qEDjhn22QG2x84F lACzNYlL2jSCEY7h8bH6Z0Vl2EoVIyH35GiM5L1e7pwsQA1ANjWkiv0NU vxNLp00YwT7qQEoxWM813yMDO0V5Bfe6z/E7/X2HHvLnDIxWwa+oBrMFa 07Jw3B3plIWZSyOrKyMk/aIDQmzSejUj2acbOJg3VULMAOuRkz9JalLPp nfCAi2qZpPEhfqBUZNRI08JcOReLjaaRBQSgiLD9pfRbmn1x4kJCk9HTm w==; X-CSE-ConnectionGUID: 4DlhooHpTCeBdSelZ/QirA== X-CSE-MsgGUID: iz+msFfAQpCkrGmHqvQ/fg== X-IronPort-AV: E=McAfee;i="6800,10657,11898"; a="89006516" X-IronPort-AV: E=Sophos;i="6.25,266,1779174000"; d="scan'208";a="89006516" Received: from orviesa006.jf.intel.com ([10.64.159.146]) by orvoesa113.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 06 Sep 2026 23:24:54 -0700 X-CSE-ConnectionGUID: bFKwFv7KTVO4D/oT8f7t0w== X-CSE-MsgGUID: UjEGOFZRTbGg5Q4Hjl2BkA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.25,266,1779174000"; d="scan'208";a="268885079" Received: from dapengmi-mobl1.ccr.corp.intel.com (HELO [10.124.241.239]) ([10.124.241.239]) by orviesa006-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 06 Sep 2026 23:24:51 -0700 Message-ID: Date: Mon, 7 Sep 2026 14:24:49 +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 LGTM. 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 */ > } >