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 C24571E7A37; Thu, 1 Aug 2024 00:40:05 +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=1722472805; cv=none; b=JmeQjLVOHplEWmFdhs8q6GlKpa0BZ4VtQO0PQvtgRH4HPP22LgI/xpdfs3kk8FnGEgE4rpI1ySN0HSQlLODn+6NXImgej46hJAGB6TKbNUtFfrIG5nWuDdsSzQgQIaQ8P5BwEm6Q9vP5e9qRyc2+dN42As6nKYoDJsm/AJd1j5A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722472805; c=relaxed/simple; bh=eLugRl+pNbrBa0y6hwdVIlCEvrzvgNE13wAef26NF6Q=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=GzFdzxw0TvUpxsC+x6x93M3X2ttlzDuxvga87TzPx4Au625YNJ3y0w8Fy1Bd3nYF47aapW4X+5rZTtzUxa9SqtgRNGg55zap8zW7y3HIGBYVqVau0iyxW7DJ+G+3vVgn95e3wKWrJrDNlCuf602lepJu8i66EndaHKH11RTDv5I= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=kx2GXqQ/; 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="kx2GXqQ/" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DDA75C116B1; Thu, 1 Aug 2024 00:40:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1722472805; bh=eLugRl+pNbrBa0y6hwdVIlCEvrzvgNE13wAef26NF6Q=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=kx2GXqQ/MgZB6O0R+cvAZH8F38NKBcT92Ok8MuyuMlo/UjA6CdDYEf/+IZ9BHT7QK gYo8USodA+PVkWM/DPRXljNzby9Kv8UPoJt2ZNg46F1JqHdT7rE35LvMrE86ZDnZfB XW9LRFATF8mzAPGVFQlFeuxkVZOjSHMormshn7PdgfgAHsmSWTYn9IjZMpnB4wT4oc 3xIa0GlOQuzZyynmWFFZqf+i0lyvlMI8K8JT4xotOWrIZpqVN0w7FXeG7Da7Fzy95x hvdeUlHjEM1rdQLoGMszx54bLT0uJ47xBHNl4jvhXzew329+FG5TXxpD5d/9bq25AL LwQzRB9SN+umw== 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 5.4 15/22] cgroup: Protect css->cgroup write under css_set_lock Date: Wed, 31 Jul 2024 20:38:44 -0400 Message-ID: <20240801003918.3939431-15-sashal@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240801003918.3939431-1-sashal@kernel.org> References: <20240801003918.3939431-1-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 5.4.281 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 62a7a50750149..16ae868941211 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -1783,9 +1783,9 @@ 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