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 DCFC518C02E; Tue, 10 Sep 2024 10:21:16 +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=1725963676; cv=none; b=HIGtnIUCNSZlbfW7En6a/2qw6Gknr+yJIGbsP7z/uubMrIE3FQ9Bamcn1EtobGRLCV/gX3l2TEL6WhuAy2s8JgLrr2cigHWlkkTkIEeIb6j/v2pu/Cjsewb/OdxR1Z1OJxj9Ce18cJgNnZjCE+JiUQxSeMI/gA/JA72OJsed2PI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1725963676; c=relaxed/simple; bh=dVt0NO9tZD3K4q+v82cHq0/xfa2m9E3/klYDLk7QZSI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Pemws3FChdJhk1tPYZ1pqd9nIHjlF6CtqSmrjX4qXinspxO/BJDIEuRy+Q3rxKyOQc/Q+H//GLuxpEqL0aZvrelUk321yhJ9IwmzzOJpx0IpeKyLtXpi8v6u5txPCQicehIyrR6R7RBOaQKP7a/k5HWQYnVpBJqRTDEHEtMgCy0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=2Q4E1qxV; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="2Q4E1qxV" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 676A9C4CEC3; Tue, 10 Sep 2024 10:21:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1725963676; bh=dVt0NO9tZD3K4q+v82cHq0/xfa2m9E3/klYDLk7QZSI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=2Q4E1qxVH1w33O3LlfWERL7pAmsxne0FXTC/8uOb8nxXXK9EZNTRPa+ssG8Po6IlA 6TTOSoIGrL9XjT8YzGqVG0Ti8eiaetCLHjAru5U4gfkvdZ57x9FMSNuqxWMoMt2UME atHHd5o8shA3TKFqB/VRk8X4IFFKy4Y2fOVw3XEM= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Waiman Long , Tejun Heo , Sasha Levin Subject: [PATCH 5.15 138/214] cgroup: Protect css->cgroup write under css_set_lock Date: Tue, 10 Sep 2024 11:32:40 +0200 Message-ID: <20240910092604.392064377@linuxfoundation.org> X-Mailer: git-send-email 2.46.0 In-Reply-To: <20240910092558.714365667@linuxfoundation.org> References: <20240910092558.714365667@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ 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 be467aea457e..84e85561a87c 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -1802,9 +1802,9 @@ 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