[PATCH AUTOSEL 6.0 06/32] cgroup: Remove data-race around cgrp_dfl_visible

Sasha Levin
2022-10-18T00:08:14Z

From: Tejun Heo <tj@kernel.org>

[ Upstream commit dc79ec1b232ad2c165d381d3dd2626df4ef9b5a4 ]

There's a seemingly harmless data-race around cgrp_dfl_visible detected by
kernel concurrency sanitizer. Let's remove it by throwing WRITE/READ_ONCE at
it.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Abhishek Shah <abhishek.shah@columbia.edu>
Cc: Gabriel Ryan <gabe@cs.columbia.edu>
Reviewed-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Link: https://lore.kernel.org/netdev/20220819072256.fn7ctciefy4fc4cu@wittgenstein/
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
kernel/cgroup/cgroup.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 5f2090d051ac..99f00a3e1997 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -2173,7 +2173,7 @@ static int cgroup_get_tree(struct fs_context *fc)
struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
int ret;

- cgrp_dfl_visible = true;
+ WRITE_ONCE(cgrp_dfl_visible, true);
cgroup_get_live(&cgrp_dfl_root.cgrp);
ctx->root = &cgrp_dfl_root;

@@ -6091,7 +6091,7 @@ int proc_cgroup_show(struct seq_file *m, struct pid_namespace *ns,
struct cgroup *cgrp;
int ssid, count = 0;

- if (root == &cgrp_dfl_root && !cgrp_dfl_visible)
+ if (root == &cgrp_dfl_root && !READ_ONCE(cgrp_dfl_visible))
continue;

seq_printf(m, "%d:", root->hierarchy_id);
--
2.35.1