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| author | Tejun Heo <tj@kernel.org> | 2017-01-26 16:47:28 -0500 |
|---|---|---|
| committer | Tejun Heo <tj@kernel.org> | 2017-01-26 16:47:28 -0500 |
| commit | 07cd12945551b63ecb1a349d50a6d69d1d6feb4a (patch) | |
| tree | 75f65eba7eac9277971082a2d5a4cf1370562c0c /kernel | |
| parent | 7ce7d89f48834cefece7804d38fc5d85382edf77 (diff) | |
| download | linux-07cd12945551b63ecb1a349d50a6d69d1d6feb4a.tar.gz | |
cgroup: don't online subsystems before cgroup_name/path() are operational
While refactoring cgroup creation, a5bca2152036 ("cgroup: factor out
cgroup_create() out of cgroup_mkdir()") incorrectly onlined subsystems
before the new cgroup is associated with it kernfs_node. This is fine
for cgroup proper but cgroup_name/path() depend on the associated
kernfs_node and if a subsystem makes the new cgroup_subsys_state
visible, which they're allowed to after onlining, it can lead to NULL
dereference.
The current code performs cgroup creation and subsystem onlining in
cgroup_create() and cgroup_mkdir() makes the cgroup and subsystems
visible afterwards. There's no reason to online the subsystems early
and we can simply drop cgroup_apply_control_enable() call from
cgroup_create() so that the subsystems are onlined and made visible at
the same time.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Fixes: a5bca2152036 ("cgroup: factor out cgroup_create() out of cgroup_mkdir()")
Cc: stable@vger.kernel.org # v4.6+
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/cgroup.c | 13 |
1 files changed, 5 insertions, 8 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 2ee9ec3051b2..688dd02af985 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -5221,6 +5221,11 @@ err_free_css: return ERR_PTR(err); } +/* + * The returned cgroup is fully initialized including its control mask, but + * it isn't associated with its kernfs_node and doesn't have the control + * mask applied. + */ static struct cgroup *cgroup_create(struct cgroup *parent) { struct cgroup_root *root = parent->root; @@ -5288,11 +5293,6 @@ static struct cgroup *cgroup_create(struct cgroup *parent) cgroup_propagate_control(cgrp); - /* @cgrp doesn't have dir yet so the following will only create csses */ - ret = cgroup_apply_control_enable(cgrp); - if (ret) - goto out_destroy; - return cgrp; out_cancel_ref: @@ -5300,9 +5300,6 @@ out_cancel_ref: out_free_cgrp: kfree(cgrp); return ERR_PTR(ret); -out_destroy: - cgroup_destroy_locked(cgrp); - return ERR_PTR(ret); } static int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name, |