From patchwork Thu Feb 2 05:26:04 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Biggers X-Patchwork-Id: 13125328 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 6644AC63797 for ; Thu, 2 Feb 2023 05:29:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231954AbjBBF3L (ORCPT ); Thu, 2 Feb 2023 00:29:11 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58794 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231970AbjBBF20 (ORCPT ); Thu, 2 Feb 2023 00:28:26 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AD39827998; Wed, 1 Feb 2023 21:28:11 -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 dfw.source.kernel.org (Postfix) with ESMTPS id 8EA94615EF; Thu, 2 Feb 2023 05:28:11 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7A436C433A1; Thu, 2 Feb 2023 05:28:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1675315691; bh=lcs6AXLIFbqkFs6UrWf0Ln1qRWrFsNHR0PXy8tOjKNA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=NjC6HerwNYZpDQWHNMEAMOutZtfItpkk143ioeMYmoqxhu5m9RxsfveJYd/9divWh UH1XXeS0GcumS5+3MeUPWE8d7Db4xX1OT0WvLTfXkHMiX3BV92mW9H3upzxduZEEM1 5dmleyl/4f0zT0C2WUinAVirG4+tKVnfWDEVkR9CNKwPeeqY/48sDwPno66qEplyOU 4KcCTTJmup/jgGr6P2U3PXtWnKmL0crqJ+xDqn9KZ9Glogzq7NIUN0iEfSzqwqA9Ak VGBIFaqph4V6WR5JffrXP2Ii1HHVozu15LGGi659U/e+etSoGfvRccQP334dNzKPMf cfN/e1iF17j6g== 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 16/16] exit: Use READ_ONCE() for all oops/warn limit reads Date: Wed, 1 Feb 2023 21:26:04 -0800 Message-Id: <20230202052604.179184-17-ebiggers@kernel.org> X-Mailer: git-send-email 2.39.1 In-Reply-To: <20230202052604.179184-1-ebiggers@kernel.org> References: <20230202052604.179184-1-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); } /**