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=-2.4 required=3.0 tests=DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,T_DKIM_INVALID, USER_AGENT_MUTT 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 D7C97C4321D for ; Fri, 24 Aug 2018 09:01:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7D01721712 for ; Fri, 24 Aug 2018 09:01:45 +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="iBdyqmMU" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7D01721712 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727464AbeHXMfY (ORCPT ); Fri, 24 Aug 2018 08:35:24 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:36062 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726768AbeHXMfY (ORCPT ); Fri, 24 Aug 2018 08:35:24 -0400 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=6+OUCC7RnGRXvLq3d7cG1dIVzq3dw6UiWQI3xhlpWNc=; b=iBdyqmMUhjco1hqMTPRgavbaJ RKQtL2QJj9Wj0KgLbYfXqMd305qvgUNemHiBYzHQ2pujrVPMdLKYHx1wtLKIdJOmAjswce6pmlWiH RQtAgMq/vy5pgEWzP8z2Sqw31Xoq4SY/neKMAWoyxixkTblZplpt5gktUrBR21qPSS9rE5r+tB+Hr AZTZWi2Zr4InXd7zeThdReyC1h2q0UvBv7CeC5Er625noyGRSiHWHTS4Z7vJ3pqmECnzwr6mTV1/H UrzvOETSFz/5/MNV9PpZMqfJEoQv5SY3t3bQtV1ld5OCcfEzlJwGjG2fOXbKT2nnRKcnPSEl+1p4e zanzcUMIQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1ft7t3-0004mM-B2; Fri, 24 Aug 2018 08:57:47 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 1D30D202E65E0; Fri, 24 Aug 2018 10:56:01 +0200 (CEST) Date: Fri, 24 Aug 2018 10:56:01 +0200 From: Peter Zijlstra To: Yabin Cui Cc: Ingo Molnar , Arnaldo Carvalho de Melo , Alexander Shishkin , Jiri Olsa , Namhyung Kim , linux-kernel@vger.kernel.org Subject: Re: [PATCH] perf: Force USER_DS when recording user stack data. Message-ID: <20180824085601.GM24124@hirez.programming.kicks-ass.net> References: <20180823225935.27035-1-yabinc@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180823225935.27035-1-yabinc@google.com> User-Agent: Mutt/1.10.0 (2018-05-17) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Aug 23, 2018 at 03:59:35PM -0700, Yabin Cui wrote: > Perf can record user stack data in response to a synchronous request, such > as a tracepoint firing. If this happens under set_fs(KERNEL_DS), then we > end up reading user stack data using __copy_from_user_inatomic() under > set_fs(KERNEL_DS). I think this conflicts with the intention of using > set_fs(KERNEL_DS). And it is explicitly forbidden by hardware on ARM64 > when both CONFIG_ARM64_UAO and CONFIG_ARM64_PAN are used. > > So fix this by forcing USER_DS when recording user stack data. > > Signed-off-by: Yabin Cui Ingo, I think this wants a stable tag too; seems to be a corrolary of: 88b0193d9418 ("perf/callchain: Force USER_DS when invoking perf_callchain_user()") Acked-by: Peter Zijlstra (Intel) > --- > kernel/events/core.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/kernel/events/core.c b/kernel/events/core.c > index 2a62b96600ad..9bc047421e75 100644 > --- a/kernel/events/core.c > +++ b/kernel/events/core.c > @@ -5948,6 +5948,7 @@ perf_output_sample_ustack(struct perf_output_handle *handle, u64 dump_size, > unsigned long sp; > unsigned int rem; > u64 dyn_size; > + mm_segment_t fs; > > /* > * We dump: > @@ -5965,7 +5966,10 @@ perf_output_sample_ustack(struct perf_output_handle *handle, u64 dump_size, > > /* Data. */ > sp = perf_user_stack_pointer(regs); > + fs = get_fs(); > + set_fs(USER_DS); > rem = __output_copy_user(handle, (void *) sp, dump_size); > + set_fs(fs); > dyn_size = dump_size - rem; > > perf_output_skip(handle, rem); > -- > 2.19.0.rc0.228.g281dcd1b4d0-goog >