From patchwork Fri Feb 3 00:27:17 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Biggers X-Patchwork-Id: 13126849 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4CEFFC636D6 for ; Fri, 3 Feb 2023 00:28:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233435AbjBCA2i (ORCPT ); Thu, 2 Feb 2023 19:28:38 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54556 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233160AbjBCA2Q (ORCPT ); Thu, 2 Feb 2023 19:28:16 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 09D1287152; Thu, 2 Feb 2023 16:28:15 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id B02F6B828D5; Fri, 3 Feb 2023 00:28:13 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D618CC4339B; Fri, 3 Feb 2023 00:28:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1675384092; bh=lcs6AXLIFbqkFs6UrWf0Ln1qRWrFsNHR0PXy8tOjKNA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=EoexD3uikQU6VS8X5XmuE7JQa6sW9w2w9FvcBydhX8AWkchHP5SZihx4nknkCiLeY cNW9DAdeq/XWdX+s3oWOzsgkBxJeSSjBdl548TFzxgERKQLAl0xyJ1wW/AXxud8ujX l32+duiXBFZzi4gCT0co2A7fySnkfIZFWIWHmc6DP0BAYigTlSEdtJpciHw8qZ5mYI 3d6MvNm0I3eRLnZnCvbf27kPGRoU/Eug3HKbGIfR2Y91v6ipM4YZ9kXiIlxDVQemWH wgJLCUcYZEc3k6A3eQVQWnA+AjMa60hDNTkYbP5g6QJbRv4HhhBHtuANffwf7fiJiq dJ85TOAoM/v3g== From: Eric Biggers To: stable@vger.kernel.org Cc: Harshit Mogalapalli , Kees Cook , SeongJae Park , Seth Jenkins , Jann Horn , "Eric W . Biederman" , linux-hardening@vger.kernel.org, linux-kernel@vger.kernel.org, Arnd Bergmann , Petr Mladek , Andrew Morton , Luis Chamberlain , Marco Elver , tangmeng , Sebastian Andrzej Siewior , Tiezhu Yang , Peter Zijlstra Subject: [PATCH 4.19 v2 15/15] exit: Use READ_ONCE() for all oops/warn limit reads Date: Thu, 2 Feb 2023 16:27:17 -0800 Message-Id: <20230203002717.49198-16-ebiggers@kernel.org> X-Mailer: git-send-email 2.39.1 In-Reply-To: <20230203002717.49198-1-ebiggers@kernel.org> References: <20230203002717.49198-1-ebiggers@kernel.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-hardening@vger.kernel.org From: Kees Cook commit 7535b832c6399b5ebfc5b53af5c51dd915ee2538 upstream. Use a temporary variable to take full advantage of READ_ONCE() behavior. Without this, the report (and even the test) might be out of sync with the initial test. Reported-by: Peter Zijlstra Link: https://lore.kernel.org/lkml/Y5x7GXeluFmZ8E0E@hirez.programming.kicks-ass.net Fixes: 9fc9e278a5c0 ("panic: Introduce warn_limit") Fixes: d4ccd54d28d3 ("exit: Put an upper limit on how often we can oops") Cc: "Eric W. Biederman" Cc: Jann Horn Cc: Arnd Bergmann Cc: Petr Mladek Cc: Andrew Morton Cc: Luis Chamberlain Cc: Marco Elver Cc: tangmeng Cc: Sebastian Andrzej Siewior Cc: Tiezhu Yang Signed-off-by: Kees Cook Signed-off-by: Eric Biggers --- kernel/exit.c | 6 ++++-- kernel/panic.c | 7 +++++-- 2 files changed, 9 insertions(+), 4 deletions(-) diff --git a/kernel/exit.c b/kernel/exit.c index b2f0aaf6bee78..02360ec3b1225 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -975,6 +975,7 @@ void __noreturn make_task_dead(int signr) * Take the task off the cpu after something catastrophic has * happened. */ + unsigned int limit; /* * Every time the system oopses, if the oops happens while a reference @@ -986,8 +987,9 @@ void __noreturn make_task_dead(int signr) * To make sure this can't happen, place an upper bound on how often the * kernel may oops without panic(). */ - if (atomic_inc_return(&oops_count) >= READ_ONCE(oops_limit) && oops_limit) - panic("Oopsed too often (kernel.oops_limit is %d)", oops_limit); + limit = READ_ONCE(oops_limit); + if (atomic_inc_return(&oops_count) >= limit && limit) + panic("Oopsed too often (kernel.oops_limit is %d)", limit); do_exit(signr); } diff --git a/kernel/panic.c b/kernel/panic.c index dbb6e27d33e10..982ecba286c08 100644 --- a/kernel/panic.c +++ b/kernel/panic.c @@ -168,12 +168,15 @@ EXPORT_SYMBOL(nmi_panic); void check_panic_on_warn(const char *origin) { + unsigned int limit; + if (panic_on_warn) panic("%s: panic_on_warn set ...\n", origin); - if (atomic_inc_return(&warn_count) >= READ_ONCE(warn_limit) && warn_limit) + limit = READ_ONCE(warn_limit); + if (atomic_inc_return(&warn_count) >= limit && limit) panic("%s: system warned too often (kernel.warn_limit is %d)", - origin, warn_limit); + origin, limit); } /**