cgroup: replace cftype->mode with CFTYPE_WORLD_WRITABLE
cftype->mode allows controllers to give arbitrary permissions to
interface knobs. Except for "cgroup.event_control", the existing uses
are spurious.
* Some explicitly specify S_IRUGO | S_IWUSR even though that's the
default.
* "cpuset.memory_pressure" specifies S_IRUGO while also setting a
write callback which returns -EACCES. All it needs to do is simply
not setting a write callback.
"cgroup.event_control" uses cftype->mode to make the file
world-writable. It's a misdesigned interface and we don't want
controllers to be tweaking interface file permissions in general.
This patch removes cftype->mode and all its spurious uses and
implements CFTYPE_WORLD_WRITABLE for "cgroup.event_control" which is
marked as compatibility-only.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index b35c4cc..e672f26 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4060,8 +4060,7 @@
{
.name = "cgroup.event_control", /* XXX: for compat */
.write = memcg_write_event_control,
- .flags = CFTYPE_NO_PREFIX,
- .mode = S_IWUGO,
+ .flags = CFTYPE_NO_PREFIX | CFTYPE_WORLD_WRITABLE,
},
{
.name = "swappiness",