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=-6.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 26BDACA90AF for ; Wed, 13 May 2020 10:02:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0781520769 for ; Wed, 13 May 2020 10:02:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1589364178; bh=eYBhrqBBMHguvSuJAyZXGOMVPTy3KnSYq6ZPfIEPdAw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=sTOA9Dy4YoPThD6G7g3jBZzPXlK6Wqd4oGggE13noXsSQJSDAWXbobME3mDkjEedG hv0dByS2/or0HP5gutN/I36asn8mXFvUF6DdG48+e0/qmcG2MiQ7T+uQ8lHUUmUzgl w0aBYtNXqihjFReQ6yDpPAMsthmbgYtcUY3v8zQ4= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388655AbgEMKC5 (ORCPT ); Wed, 13 May 2020 06:02:57 -0400 Received: from mail.kernel.org ([198.145.29.99]:48746 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1733265AbgEMJtf (ORCPT ); Wed, 13 May 2020 05:49:35 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id E6F1C20740; Wed, 13 May 2020 09:49:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1589363375; bh=eYBhrqBBMHguvSuJAyZXGOMVPTy3KnSYq6ZPfIEPdAw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=QpTIlMD3FtjEH4OkQ1kZux9ftC/+167RsI9k76Vl98cPn8kc4UmAFddtuyGpr3xIi z1FZPMrs9vwpVYU8Q1lNEjYQb7I1jOcKkt+Lz6yUuK5twgwlGIeZqQusdzLYqNgq7v k7bpi3FJzHQLXv1qPAQn+v122RGzTb7a+HvPlq74= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, "Tzvetomir Stoyanov (VMware)" , Joerg Roedel , "Steven Rostedt (VMware)" Subject: [PATCH 5.4 49/90] tracing: Add a vmalloc_sync_mappings() for safe measure Date: Wed, 13 May 2020 11:44:45 +0200 Message-Id: <20200513094414.002896061@linuxfoundation.org> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20200513094408.810028856@linuxfoundation.org> References: <20200513094408.810028856@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Steven Rostedt (VMware) commit 11f5efc3ab66284f7aaacc926e9351d658e2577b upstream. x86_64 lazily maps in the vmalloc pages, and the way this works with per_cpu areas can be complex, to say the least. Mappings may happen at boot up, and if nothing synchronizes the page tables, those page mappings may not be synced till they are used. This causes issues for anything that might touch one of those mappings in the path of the page fault handler. When one of those unmapped mappings is touched in the page fault handler, it will cause another page fault, which in turn will cause a page fault, and leave us in a loop of page faults. Commit 763802b53a42 ("x86/mm: split vmalloc_sync_all()") split vmalloc_sync_all() into vmalloc_sync_unmappings() and vmalloc_sync_mappings(), as on system exit, it did not need to do a full sync on x86_64 (although it still needed to be done on x86_32). By chance, the vmalloc_sync_all() would synchronize the page mappings done at boot up and prevent the per cpu area from being a problem for tracing in the page fault handler. But when that synchronization in the exit of a task became a nop, it caused the problem to appear. Link: https://lore.kernel.org/r/20200429054857.66e8e333@oasis.local.home Cc: stable@vger.kernel.org Fixes: 737223fbca3b1 ("tracing: Consolidate buffer allocation code") Reported-by: "Tzvetomir Stoyanov (VMware)" Suggested-by: Joerg Roedel Signed-off-by: Steven Rostedt (VMware) Signed-off-by: Greg Kroah-Hartman --- kernel/trace/trace.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -8318,6 +8318,19 @@ static int allocate_trace_buffers(struct */ allocate_snapshot = false; #endif + + /* + * Because of some magic with the way alloc_percpu() works on + * x86_64, we need to synchronize the pgd of all the tables, + * otherwise the trace events that happen in x86_64 page fault + * handlers can't cope with accessing the chance that a + * alloc_percpu()'d memory might be touched in the page fault trace + * event. Oh, and we need to audit all other alloc_percpu() and vmalloc() + * calls in tracing, because something might get triggered within a + * page fault trace event! + */ + vmalloc_sync_mappings(); + return 0; }