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=-8.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 6A814C43603 for ; Tue, 10 Dec 2019 15:35:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3C6ED20828 for ; Tue, 10 Dec 2019 15:35:50 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="TKSE5/SV" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727505AbfLJPft (ORCPT ); Tue, 10 Dec 2019 10:35:49 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:40070 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727380AbfLJPfs (ORCPT ); Tue, 10 Dec 2019 10:35:48 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=lZYXwP0ni4XYi2YYlu9VVenpwLLmSfDHgkVywliZ2Ew=; b=TKSE5/SV3Q4191WpyeITcbWKB XZEL2twvP0MmrdwQqFpY/fHrfQbsJlr20oT+TNxookvYrvDmzxNtio+KSt956Okbk1TllUeWJaRIr Sc1x4KYpvNyibbf3FFOFBwqspqc1x2+vpyfM8DdwJN3kO+q1PZOl3GFz+N1jQNVGFDWEfZkIRhH1F j1Yq0zI9C+aJ6AlqeD7nkZ+9yNCVCGG8nEi5O5tfS3vFVoOZYTh4MQ4i4Vg3R7FqkMNWVEgdmOiHe y5lYgVu8Tybf9Wl/2vp60WvN1KxEnJ1myRBjH12NWFeqPSKsGCfht9hEO3xn52ERr6gd5qOpmUwAC OJvkxljlQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1iehYC-0003Rl-1Z; Tue, 10 Dec 2019 15:35:48 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id DD69C305DD6; Tue, 10 Dec 2019 16:34:26 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 66E2229E07076; Tue, 10 Dec 2019 16:35:46 +0100 (CET) Date: Tue, 10 Dec 2019 16:35:46 +0100 From: Peter Zijlstra To: Alexander Shishkin Cc: Arnaldo Carvalho de Melo , Ingo Molnar , linux-kernel@vger.kernel.org, Jiri Olsa Subject: Re: [PATCH 2/2] perf/x86/intel/bts: Fix the use of page_private() Message-ID: <20191210153546.GO2844@hirez.programming.kicks-ass.net> References: <20191205142853.28894-1-alexander.shishkin@linux.intel.com> <20191205142853.28894-3-alexander.shishkin@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191205142853.28894-3-alexander.shishkin@linux.intel.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Dec 05, 2019 at 05:28:53PM +0300, Alexander Shishkin wrote: > Commit > > 8062382c8dbe2 ("perf/x86/intel/bts: Add BTS PMU driver") > > uses page_private(page) without checking the PagePrivate(page) first, Well, arguably it did check it, but you didn't like that WARN ;-) > which seems like a potential bug, considering that page->private aliases > with other stuff in struct page. > > Fix this by checking PagePrivate() first. > > Signed-off-by: Alexander Shishkin > Fixes: 8062382c8dbe2 ("perf/x86/intel/bts: Add BTS PMU driver") > --- > arch/x86/events/intel/bts.c | 14 +++++++++++--- > 1 file changed, 11 insertions(+), 3 deletions(-) > > diff --git a/arch/x86/events/intel/bts.c b/arch/x86/events/intel/bts.c > index d53b4fb86d87..9e4da1c5a129 100644 > --- a/arch/x86/events/intel/bts.c > +++ b/arch/x86/events/intel/bts.c > @@ -63,9 +63,17 @@ struct bts_buffer { > > static struct pmu bts_pmu; > > +static int buf_nr_pages(struct page *page) > +{ > + if (!PagePrivate(page)) > + return 1; > + > + return 1 << page_private(page); > +} Yes, that seems like a sensible helper.