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 X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A5179C388F7 for ; Thu, 22 Oct 2020 12:49:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 51D3C223BF for ; Thu, 22 Oct 2020 12:49:56 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=mg.codeaurora.org header.i=@mg.codeaurora.org header.b="NRkfpHlg" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2898968AbgJVMtz (ORCPT ); Thu, 22 Oct 2020 08:49:55 -0400 Received: from z5.mailgun.us ([104.130.96.5]:47032 "EHLO z5.mailgun.us" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2898947AbgJVMty (ORCPT ); Thu, 22 Oct 2020 08:49:54 -0400 DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg.codeaurora.org; q=dns/txt; s=smtp; t=1603370994; h=Message-ID: References: In-Reply-To: Subject: Cc: To: From: Date: Content-Transfer-Encoding: Content-Type: MIME-Version: Sender; bh=RCK7B2J1TXHqhKnVahkoy/BJVO0J46HHa0PpEK+JktM=; b=NRkfpHlgUX1HKbrA/8S3zYnM/HkOK5pgvTLGt+KtYzjdP97MEh3IgvYtpdcEAzO1P86JN5ZB OP6DD0eY5kH4yLvdvTQg0wU6/waGeAOAWXZxhIPTeDlVqqacYFe3fl2OFO+6ihbzuk27VzZg jM1zlxzNZx6lJLtwDXZZE44ciuE= X-Mailgun-Sending-Ip: 104.130.96.5 X-Mailgun-Sid: WyI1MzIzYiIsICJsaW51eC1hcm0tbXNtQHZnZXIua2VybmVsLm9yZyIsICJiZTllNGEiXQ== Received: from smtp.codeaurora.org (ec2-35-166-182-171.us-west-2.compute.amazonaws.com [35.166.182.171]) by smtp-out-n05.prod.us-west-2.postgun.com with SMTP id 5f917fe206d81bc48d5bec06 (version=TLS1.2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256); Thu, 22 Oct 2020 12:49:38 GMT Sender: saiprakash.ranjan=codeaurora.org@mg.codeaurora.org Received: by smtp.codeaurora.org (Postfix, from userid 1001) id C8870C433C9; Thu, 22 Oct 2020 12:49:38 +0000 (UTC) Received: from mail.codeaurora.org (localhost.localdomain [127.0.0.1]) (using TLSv1 with cipher ECDHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) (Authenticated sender: saiprakash.ranjan) by smtp.codeaurora.org (Postfix) with ESMTPSA id EFD4CC43387; Thu, 22 Oct 2020 12:49:37 +0000 (UTC) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Thu, 22 Oct 2020 18:19:37 +0530 From: Sai Prakash Ranjan To: Peter Zijlstra Cc: Mark Rutland , Mathieu Poirier , Suzuki K Poulose , Alexander Shishkin , linux-arm-msm@vger.kernel.org, coresight@lists.linaro.org, linux-kernel@vger.kernel.org, Arnaldo Carvalho de Melo , Stephen Boyd , Ingo Molnar , Namhyung Kim , Jiri Olsa , linux-arm-kernel@lists.infradead.org, Mike Leach Subject: Re: [PATCHv2 2/4] coresight: tmc-etf: Fix NULL ptr dereference in tmc_enable_etf_sink_perf() In-Reply-To: <20201022113214.GD2611@hirez.programming.kicks-ass.net> References: <20201022113214.GD2611@hirez.programming.kicks-ass.net> Message-ID: X-Sender: saiprakash.ranjan@codeaurora.org User-Agent: Roundcube Webmail/1.3.9 Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org On 2020-10-22 17:02, Peter Zijlstra wrote: > On Thu, Oct 22, 2020 at 04:27:52PM +0530, Sai Prakash Ranjan wrote: > >> Looking at the ETR and other places in the kernel, ETF and the >> ETB are the only places trying to dereference the task(owner) >> in tmc_enable_etf_sink_perf() which is also called from the >> sched_in path as in the call trace. > >> @@ -391,6 +392,10 @@ static void *tmc_alloc_etf_buffer(struct >> coresight_device *csdev, >> { >> int node; >> struct cs_buffers *buf; >> + struct task_struct *task = READ_ONCE(event->owner); >> + >> + if (!task || is_kernel_event(event)) >> + return NULL; > > > This is *wrong*... why do you care about who owns the events? > The original issue was the owner being NULL and causing a NULL pointer dereference. I did ask some time back if it is valid for the owner to be NULL [1] and should probably be handled in events core? [1] https://lore.kernel.org/lkml/c0e1f99a0a2480dfc8d788bb424d3f08@codeaurora.org/ Unable to handle kernel NULL pointer dereference at virtual address 0000000000000548 Mem abort info: ESR = 0x96000006 EC = 0x25: DABT (current EL), IL = 32 bits SET = 0, FnV = 0 EA = 0, S1PTW = 0 Data abort info: ISV = 0, ISS = 0x00000006 CM = 0, WnR = 0 ... Call trace: tmc_enable_etf_sink+0xe4/0x280 coresight_enable_path+0x168/0x1fc etm_event_start+0x8c/0xf8 etm_event_add+0x38/0x54 event_sched_in+0x194/0x2ac group_sched_in+0x54/0x12c flexible_sched_in+0xd8/0x120 visit_groups_merge+0x100/0x16c ctx_flexible_sched_in+0x50/0x74 ctx_sched_in+0xa4/0xa8 perf_event_sched_in+0x60/0x6c perf_event_context_sched_in+0x98/0xe0 __perf_event_task_sched_in+0x5c/0xd8 finish_task_switch+0x184/0x1cc schedule_tail+0x20/0xec ret_from_fork+0x4/0x18 Thanks, Sai -- QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation