From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BAD9213775B; Thu, 1 Aug 2024 00:38:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722472716; cv=none; b=t2X85M83idemW5zmTMXMjxvWdxL/hUGCosLcrS+hNo/cVoZe0B1b8NgjvNo2jftU2lUV7iz1i5LHHbjeBm8d0wvZmGzwjAQXb9iHd/CSit88ln2/cnY4e1IY2axrLi9XsTLXBlIBEpU+NfzDMxfcW9d7anfuhO01yldER1/eGw8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722472716; c=relaxed/simple; bh=G18znVv8Awy0nqLe3UcKJM8x74ytyQbdXqD68nCkYLU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=r+UyYe035eet90jwcR408XYtEFwECi3XeYETXbiMLbd+QrZi3q0h68eCAuhRFHzoOdcRIVi4Aquk4cqGV8AZz2e1AavDANnzlVJjbW23juojvxDMDf03fHjulfuDRA88B8unR7cPi7W67ZyJ+WvHvUXog/w++FQ4AliEfn+zkmo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=qBnHy4ZT; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="qBnHy4ZT" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 377C5C116B1; Thu, 1 Aug 2024 00:38:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1722472716; bh=G18znVv8Awy0nqLe3UcKJM8x74ytyQbdXqD68nCkYLU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=qBnHy4ZTtCyRVz6umH4CCb+7ytLp8vqh2D5MTyAtTHCc206otFxXvHyoWTVbYkyZ5 x4WvV2b4tgb/sOPseoaEBc7pjnJpdMhG/TqmmjIecBPeY8scQZTnTOZA9z/pQ2bEMg aGa0Blk80VOfJpID+JSLQVjoaXyT58VCCGz5JMQG6WaOD05vUYG897BiQT6zQw5Y7M wlE+XlpPqNIYQ/RfyR+ysmQCNgFoTzBtQzc7O4ojHUzG4Uhb4IiDe2Zwc/+87+eB1j 9zyIzcND1LyioToOVFSszoZkrzYC5MROQelrxrmHZgJujDfVFXS/6PcJBFsJjUKCXR ssz/VFJDcqpvg== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Waiman Long , Tejun Heo , Sasha Levin , lizefan.x@bytedance.com, hannes@cmpxchg.org, mkoutny@suse.com, cgroups@vger.kernel.org Subject: [PATCH AUTOSEL 5.10 31/38] cgroup: Protect css->cgroup write under css_set_lock Date: Wed, 31 Jul 2024 20:35:37 -0400 Message-ID: <20240801003643.3938534-31-sashal@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240801003643.3938534-1-sashal@kernel.org> References: <20240801003643.3938534-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 5.10.223 Content-Transfer-Encoding: 8bit From: Waiman Long [ Upstream commit 57b56d16800e8961278ecff0dc755d46c4575092 ] The writing of css->cgroup associated with the cgroup root in rebind_subsystems() is currently protected only by cgroup_mutex. However, the reading of css->cgroup in both proc_cpuset_show() and proc_cgroup_show() is protected just by css_set_lock. That makes the readers susceptible to racing problems like data tearing or caching. It is also a problem that can be reported by KCSAN. This can be fixed by using READ_ONCE() and WRITE_ONCE() to access css->cgroup. Alternatively, the writing of css->cgroup can be moved under css_set_lock as well which is done by this patch. Signed-off-by: Waiman Long Signed-off-by: Tejun Heo Signed-off-by: Sasha Levin --- kernel/cgroup/cgroup.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index 11400eba61242..e7b84b754748c 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -1773,9 +1773,9 @@ int rebind_subsystems(struct cgroup_root *dst_root, u16 ss_mask) RCU_INIT_POINTER(scgrp->subsys[ssid], NULL); rcu_assign_pointer(dcgrp->subsys[ssid], css); ss->root = dst_root; - css->cgroup = dcgrp; spin_lock_irq(&css_set_lock); + css->cgroup = dcgrp; WARN_ON(!list_empty(&dcgrp->e_csets[ss->id])); list_for_each_entry_safe(cset, cset_pos, &scgrp->e_csets[ss->id], e_cset_node[ss->id]) { -- 2.43.0