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Message-Id: <20220412192459.227740-1-tadeusz.struk@linaro.org> Date: Tue, 12 Apr 2022 12:24:59 -0700 From: Tadeusz Struk <tadeusz.struk@...aro.org> To: cgroups@...r.kernel.org Cc: Tadeusz Struk <tadeusz.struk@...aro.org>, Tejun Heo <tj@...nel.org>, Zefan Li <lizefan.x@...edance.com>, Johannes Weiner <hannes@...xchg.org>, Christian Brauner <brauner@...nel.org>, Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, Andrii Nakryiko <andrii@...nel.org>, Martin KaFai Lau <kafai@...com>, Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>, John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>, netdev@...r.kernel.org, bpf@...r.kernel.org, stable@...r.kernel.org, linux-kernel@...r.kernel.org, syzbot+e42ae441c3b10acf9e9d@...kaller.appspotmail.com Subject: [PATCH] cgroup: don't queue css_release_work if one already pending Syzbot found a corrupted list bug scenario that can be triggered from cgroup css_create(). The reproduces writes to cgroup.subtree_control file, which invokes cgroup_apply_control_enable(), css_create(), and css_populate_dir(), which then randomly fails with a fault injected -ENOMEM. In such scenario the css_create() error path rcu enqueues css_free_rwork_fn work for an css->refcnt initialized with css_release() destructor, and there is a chance that the css_release() function will be invoked for a cgroup_subsys_state, for which a destroy_work has already been queued via css_create() error path. This causes a list_add corruption as can be seen in the syzkaller report [1]. This can be avoided by adding a check to css_release() that checks if it has already been enqueued. [1] https://syzkaller.appspot.com/bug?id=e26e54d6eac9d9fb50b221ec3e4627b327465dbd Cc: Tejun Heo <tj@...nel.org> Cc: Zefan Li <lizefan.x@...edance.com> Cc: Johannes Weiner <hannes@...xchg.org> Cc: Christian Brauner <brauner@...nel.org> Cc: Alexei Starovoitov <ast@...nel.org> Cc: Daniel Borkmann <daniel@...earbox.net> Cc: Andrii Nakryiko <andrii@...nel.org> Cc: Martin KaFai Lau <kafai@...com> Cc: Song Liu <songliubraving@...com> Cc: Yonghong Song <yhs@...com> Cc: John Fastabend <john.fastabend@...il.com> Cc: KP Singh <kpsingh@...nel.org> Cc: <cgroups@...r.kernel.org> Cc: <netdev@...r.kernel.org> Cc: <bpf@...r.kernel.org> Cc: <stable@...r.kernel.org> Cc: <linux-kernel@...r.kernel.org> Reported-by: syzbot+e42ae441c3b10acf9e9d@...kaller.appspotmail.com Fixes: 8f36aaec9c92 ("cgroup: Use rcu_work instead of explicit rcu and work item") Signed-off-by: Tadeusz Struk <tadeusz.struk@...aro.org> --- kernel/cgroup/cgroup.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index adb820e98f24..9ae2de29f8c9 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -5210,8 +5210,11 @@ static void css_release(struct percpu_ref *ref) struct cgroup_subsys_state *css = container_of(ref, struct cgroup_subsys_state, refcnt); - INIT_WORK(&css->destroy_work, css_release_work_fn); - queue_work(cgroup_destroy_wq, &css->destroy_work); + if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, + work_data_bits(&css->destroy_work))) { + INIT_WORK(&css->destroy_work, css_release_work_fn); + queue_work(cgroup_destroy_wq, &css->destroy_work); + } } static void init_and_link_css(struct cgroup_subsys_state *css, -- 2.35.1
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