From patchwork Thu Feb 2 05:44:06 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Biggers X-Patchwork-Id: 13125357 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 7ACCAC64EC7 for ; Thu, 2 Feb 2023 05:45:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231149AbjBBFp6 (ORCPT ); Thu, 2 Feb 2023 00:45:58 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41334 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231463AbjBBFpg (ORCPT ); Thu, 2 Feb 2023 00:45:36 -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 89A174DBEC; Wed, 1 Feb 2023 21:45:31 -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 CB67F61883; Thu, 2 Feb 2023 05:45:30 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id B7C01C4339E; Thu, 2 Feb 2023 05:45:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1675316730; bh=PezzPrlLFd7Q51QZ1OXqNb3IL9FpXtGge3PpuUfRJNk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=CoTtGhvsMHnMkgjeHZ+eFrE4S4bMahykAc9CQ03gcOQHNllnQhu9wWjiN+Y7aIjag gV3ut6lO9JgnQA2iY+0twwpoW+hQQJhZSGGNGhUjykgPyKfVic2X3HIEC/D1WOp6kS x3ajWJDjZgl3tPYlQ5LT8oiyg2bhFc/Mj4ZK9Pg/NjXZRWtOXulVeRdf8WygjoN6Ec vt98OkN9Fj88m2x7n+lOHh+Ymd68/b9IGzvrukYEc3nGqHeb3XJqMvS45M97PKe/pM JvHGSBQ9+ysPLiFrmvudjYD5uGX+lNxGbvHtlaaWzyV5MHuVpAf9VDZ5AEp0+aw4hv i+O196/ljCWlw== 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 4.14 16/16] exit: Use READ_ONCE() for all oops/warn limit reads Date: Wed, 1 Feb 2023 21:44:06 -0800 Message-Id: <20230202054406.221721-17-ebiggers@kernel.org> X-Mailer: git-send-email 2.39.1 In-Reply-To: <20230202054406.221721-1-ebiggers@kernel.org> References: <20230202054406.221721-1-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 73103e008a627..c0ff4461643d0 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -973,6 +973,7 @@ 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 @@ -984,8 +985,9 @@ 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 8f7bf0a8cef1a..165fd747cebd0 100644 --- a/kernel/panic.c +++ b/kernel/panic.c @@ -165,12 +165,15 @@ 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); } /**