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=-9.8 required=3.0 tests=BAYES_00,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 6E297C2D0A3 for ; Mon, 9 Nov 2020 13:27:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2F05F206ED for ; Mon, 9 Nov 2020 13:27:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604928470; bh=VaIpHISW1bHeg0YK+bGy4dB54g61d2RgvK3sQTLnD6w=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=01CFdKcURvwDVTu6LZg1i+n2C4TfMKablm0ncU/YFNsXWmmWCek5ff1kDYqDvQf0s Oi7NhJzrCtOfpgnu5fI3KfDVNwGlbGcuhkwqROxKT4QJX3Lzm8SrogNZUbtqKNXjxq 1iq1sd5iRPh84NpEsoE1vDwiQPgLaqBjL/tl/oEc= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1733165AbgKINOc (ORCPT ); Mon, 9 Nov 2020 08:14:32 -0500 Received: from mail.kernel.org ([198.145.29.99]:40806 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1733149AbgKINO2 (ORCPT ); Mon, 9 Nov 2020 08:14:28 -0500 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (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 BC71220789; Mon, 9 Nov 2020 13:14:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604927668; bh=VaIpHISW1bHeg0YK+bGy4dB54g61d2RgvK3sQTLnD6w=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=MfYuJOahE1fbIShIubfDzwK6POVkcxBipckNONQXzhmqdRDfwA+vhjbnW4IGT4Cwp iZhACYpyyuY2bET0VoAH6h8w50BezpIMnj+B8HbQykDNYiu7PJ32KSCjCs0SoxHn7a bAb+8Au5uuZd/nCELhX9yaVfE89gD35mM8LWp8zo= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, "Steven Rostedt (VMware)" Subject: [PATCH 5.4 36/85] ftrace: Fix recursion check for NMI test Date: Mon, 9 Nov 2020 13:55:33 +0100 Message-Id: <20201109125024.330189877@linuxfoundation.org> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20201109125022.614792961@linuxfoundation.org> References: <20201109125022.614792961@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Steven Rostedt (VMware) commit ee11b93f95eabdf8198edd4668bf9102e7248270 upstream. The code that checks recursion will work to only do the recursion check once if there's nested checks. The top one will do the check, the other nested checks will see recursion was already checked and return zero for its "bit". On the return side, nothing will be done if the "bit" is zero. The problem is that zero is returned for the "good" bit when in NMI context. This will set the bit for NMIs making it look like *all* NMI tracing is recursing, and prevent tracing of anything in NMI context! The simple fix is to return "bit + 1" and subtract that bit on the end to get the real bit. Cc: stable@vger.kernel.org Fixes: edc15cafcbfa3 ("tracing: Avoid unnecessary multiple recursion checks") Signed-off-by: Steven Rostedt (VMware) Signed-off-by: Greg Kroah-Hartman --- kernel/trace/trace.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/kernel/trace/trace.h +++ b/kernel/trace/trace.h @@ -653,7 +653,7 @@ static __always_inline int trace_test_an current->trace_recursion = val; barrier(); - return bit; + return bit + 1; } static __always_inline void trace_clear_recursion(int bit) @@ -663,6 +663,7 @@ static __always_inline void trace_clear_ if (!bit) return; + bit--; bit = 1 << bit; val &= ~bit;