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 72CD1188CC1; Tue, 10 Sep 2024 09:50:43 +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=1725961843; cv=none; b=uX1IQEeym81hEDXvH+ZNNH4XPbY/mPeaBdl2gV4nQgrlEe8wa5yRn1MSh43rnOHRolL7yMQ91eJ2B4MxA53jhVk03LJ+T8J/mr4pDs8/5x6d4Cfq0QaUJbGgBwQkOGYsd6OyjBtxXgQA+JXbO1ViySSvsM8wEvu2dShyg20cWss= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1725961843; c=relaxed/simple; bh=nA3olkvI+lWlF1BrjGr+B8DP/suqe+aXMf/NCQYpefM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=S42zmmXeVpxIon771VQuufrtx0RzlZ6nCqpidCF3/aOsKzesU7g3ZRU69cC0eWs5Yf0LUR+FTjxrfrUUYDTa7SvOiDFsqpUc1loH9/+L9KjbpxCosZ9lMv4rlRdhNEoC+CNekYeirTRcvCz+5bnXWUtN1NAClTvN+rD0+EQJTkE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=QD0Y3vXM; 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="QD0Y3vXM" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DEFE3C4CEC6; Tue, 10 Sep 2024 09:50:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1725961843; bh=nA3olkvI+lWlF1BrjGr+B8DP/suqe+aXMf/NCQYpefM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=QD0Y3vXMw9kWjgM609OVQkSXQLYhCw9tIA4VPE2npl7ZP4sO8QPZrMFfeXCYIENgB jew5myJPRAC3VpIV8KDDqYyCrT7/LmKoQgp4pE9B/Cm+laEjN3Cue2m2eZkCOm3oTr h5v1dB6oYHDOJZiBGA7SZK0AusIhERjz0cc4+Eqs= 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 6.10 208/375] cgroup: Protect css->cgroup write under css_set_lock Date: Tue, 10 Sep 2024 11:30:05 +0200 Message-ID: <20240910092629.496448412@linuxfoundation.org> X-Mailer: git-send-email 2.46.0 In-Reply-To: <20240910092622.245959861@linuxfoundation.org> References: <20240910092622.245959861@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.10-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 e32b6972c478..278889170f94 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -1839,9 +1839,9 @@ 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