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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 95AC4C5475B for ; Wed, 6 Mar 2024 15:52:36 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 272806B008A; Wed, 6 Mar 2024 10:52:36 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 222B66B008C; Wed, 6 Mar 2024 10:52:36 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1388B6B0092; Wed, 6 Mar 2024 10:52:36 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id 024436B008A for ; Wed, 6 Mar 2024 10:52:36 -0500 (EST) Received: from smtpin30.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id C1445120B28 for ; Wed, 6 Mar 2024 15:52:35 +0000 (UTC) X-FDA: 81867056670.30.FF36478 Received: from sin.source.kernel.org (sin.source.kernel.org [145.40.73.55]) by imf21.hostedemail.com (Postfix) with ESMTP id 7E7111C0006 for ; Wed, 6 Mar 2024 15:52:33 +0000 (UTC) Authentication-Results: imf21.hostedemail.com; dkim=none; spf=pass (imf21.hostedemail.com: domain of "SRS0=fIXh=KM=goodmis.org=rostedt@kernel.org" designates 145.40.73.55 as permitted sender) smtp.mailfrom="SRS0=fIXh=KM=goodmis.org=rostedt@kernel.org"; dmarc=none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1709740354; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=wacGfOo2010VaHWQ15vn6fY1u01apQ5am33kmd/xfOI=; b=a0JxrxWhZPvEkV+Pp9bUmLg5DJMDWY08mvmzB0fGK2sdCehX2eVWblxilYjQFvqcgXuYCI oaMK81I6CvXFoBT1QKIVl5o4yyn6rZDUnXhSNaXwLqf4cwUzg+xniSynO28qOBDX5SjqUj eKJ+N0NWpncj6b5+sg26z9kDAKwvS3c= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1709740354; a=rsa-sha256; cv=none; b=PwjQoBtl/fftaOr1PTuZyAFZde9096RRemBwWtViC5Dyh/mRsu6NRYThpKWfea9gasU7eV BN1xXLlrhMIU1gn+d1M+RTzfWxSbjS4SVmBp1ZsB2cfqJ5BF6IccxQs/StSwo0HBMIGiem 4L3Y+nVhLXZ/H3mNcFfgoHNNqMa6a4o= ARC-Authentication-Results: i=1; imf21.hostedemail.com; dkim=none; spf=pass (imf21.hostedemail.com: domain of "SRS0=fIXh=KM=goodmis.org=rostedt@kernel.org" designates 145.40.73.55 as permitted sender) smtp.mailfrom="SRS0=fIXh=KM=goodmis.org=rostedt@kernel.org"; dmarc=none Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sin.source.kernel.org (Postfix) with ESMTP id 69534CE2255; Wed, 6 Mar 2024 15:52:30 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7B865C433C7; Wed, 6 Mar 2024 15:52:28 +0000 (UTC) Date: Wed, 6 Mar 2024 10:54:20 -0500 From: Steven Rostedt To: Sam Sun Cc: linux-kernel@vger.kernel.org, syzkaller@googlegroups.com, xrivendell7@gmail.com, ardb@kernel.org, jbaron@akamai.com, jpoimboe@kernel.org, peterz@infradead.org, linux-mm@kvack.org, akpm@linux-foundation.org Subject: Re: [Bug] WARNING in static_key_disable_cpuslocked Message-ID: <20240306105420.6a6bea2c@gandalf.local.home> In-Reply-To: References: X-Mailer: Claws Mail 3.19.1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Stat-Signature: 6emozfkbz36i371w6jcuk944kgn3hbk3 X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 7E7111C0006 X-Rspam-User: X-HE-Tag: 1709740353-856934 X-HE-Meta: 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 Ey6L9Le5 GU96VfHifYR1CHGeInGnEK3RwKrDwrdsxpp/k77v+WicUfflulF03mgcpg+Tvukyx3pUlgvqjPkJioUTr4mkECGCssmvOHDyMAadj4WFwbwd/Edk5hCqZiu1d5E2NcMn9QACwmPYE1goKtuQz0etkUkMuEJZmJaZlKJ5bWLWSQznnV9JTxGc+xz3M3ZG4/4viiCCR0+6gvGzJ9OqAN2BzHDvJLQnMBHKrNwLNgD1qXfW9zu/3KplFC7PZ8XYvR4HY6jQftajqiGWwGnUN6scPDSji3lUHhDpF0zwKz6m+ST8Q2n34TzmzlXOb8J/gpFGi89l96gJzkS47UJ83wPDRz3fTKnlM45XhW2Esqx0OWDQ6HtdcPGchA2D87I3HXTEEkt3862afgr64iOYXolE3I0FOeg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, 5 Mar 2024 15:54:24 +0800 Sam Sun wrote: > We analyzed the cause of this bug. It seems that in function > static_key_disable_cpuslocked(), there is a small racing window > between two atomic_read(&key->enabled) in line 228 & 229, triggering > the WARN_ON_ONCE macro. This might cause function returned without > actually disabling the static_key "key". I am not sure if there is any > other potential threat here. > > I searched on web and found that there was a similar bug reported by > syzbot several years ago > (https://groups.google.com/g/syzkaller-bugs/c/_W3lgRCwlb4/m/TqzyQcPpAQAJ). > At that time the fix was in the net instead of kernel/jump_label.c. So > I checked the call stack and cc this email to memory management > maintainers. Hope there is no confusion. > > If you have any questions, please contact us. > Reported by: Yue Sun > Reported by: xingwei lee Thanks for the report. I wonder if it simply needs to add the tests in the locking? Like the patch below. Because I could see: CPU 0 CPU 1 ----- ----- key->enabled = 0 static_key_enable_cpus_locked() jump_label_lock(); static_key_disable_cpus_locked() if (key->enabled != 1) { key->enabled = 1; WARN_ON(key->enabled != 0) Now I guess the question is, why is something trying to disable something that is not enabled? Is the above scenario OK? Or should the users of static_key also prevent this? -- Steve diff --git a/kernel/jump_label.c b/kernel/jump_label.c index d9c822bbffb8..f154caf2a62b 100644 --- a/kernel/jump_label.c +++ b/kernel/jump_label.c @@ -194,12 +194,12 @@ void static_key_enable_cpuslocked(struct static_key *key) STATIC_KEY_CHECK_USE(key); lockdep_assert_cpus_held(); + jump_label_lock(); if (atomic_read(&key->enabled) > 0) { WARN_ON_ONCE(atomic_read(&key->enabled) != 1); - return; + goto unlock; } - jump_label_lock(); if (atomic_read(&key->enabled) == 0) { atomic_set(&key->enabled, -1); jump_label_update(key); @@ -208,6 +208,7 @@ void static_key_enable_cpuslocked(struct static_key *key) */ atomic_set_release(&key->enabled, 1); } +unlock: jump_label_unlock(); } EXPORT_SYMBOL_GPL(static_key_enable_cpuslocked); @@ -225,14 +226,15 @@ void static_key_disable_cpuslocked(struct static_key *key) STATIC_KEY_CHECK_USE(key); lockdep_assert_cpus_held(); + jump_label_lock(); if (atomic_read(&key->enabled) != 1) { WARN_ON_ONCE(atomic_read(&key->enabled) != 0); - return; + goto unlock; } - jump_label_lock(); if (atomic_cmpxchg(&key->enabled, 1, 0)) jump_label_update(key); +unlock: jump_label_unlock(); } EXPORT_SYMBOL_GPL(static_key_disable_cpuslocked);