From: Tadeusz Struk <tadeusz.struk@linaro.org>
To: Tejun Heo <tj@kernel.org>
Cc: Michal Koutny <mkoutny@suse.com>,
Zefan Li <lizefan.x@bytedance.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Christian Brauner <brauner@kernel.org>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
Yonghong Song <yhs@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@kernel.org>,
cgroups@vger.kernel.org, netdev@vger.kernel.org,
bpf@vger.kernel.org, stable@vger.kernel.org,
linux-kernel@vger.kernel.org,
syzbot+e42ae441c3b10acf9e9d@syzkaller.appspotmail.com
Subject: Re: [PATCH v2] cgroup: serialize css kill and release paths
Date: Fri, 3 Jun 2022 11:17:23 -0700 [thread overview]
Message-ID: <0c37c2b9-a89a-54d7-9fd3-f035f6816aa8@linaro.org> (raw)
In-Reply-To: <20220603181321.443716-1-tadeusz.struk@linaro.org>
On 6/3/22 11:13, Tadeusz Struk wrote:
> Syzbot found a corrupted list bug scenario that can be triggered from
> cgroup_subtree_control_write(cgrp). The reproduces writes to
> cgroup.subtree_control file, which invokes:
> cgroup_apply_control_enable()->css_create()->css_populate_dir(), which
> then fails with a fault injected -ENOMEM.
> In such scenario the css_killed_work_fn will be en-queued via
> cgroup_apply_control_disable(cgrp)->kill_css(css), and bail out to
> cgroup_kn_unlock(). Then cgroup_kn_unlock() will call:
> cgroup_put(cgrp)->css_put(&cgrp->self), which will try to enqueue
> css_release_work_fn for the same css instance, causing a list_add
> corruption bug, as can be seen in the syzkaller report [1].
>
> Fix this by synchronizing the css ref_kill and css_release jobs.
> css_release() function will check if the css_killed_work_fn() has been
> scheduled for the css and only en-queue the css_release_work_fn()
> if css_killed_work_fn wasn't already en-queued. Otherwise css_release() will
> set the CSS_REL_LATER flag for that css. This will cause the
> css_release_work_fn() work to be executed after css_killed_work_fn() is finished.
>
> Two scc flags have been introduced to implement this serialization mechanizm:
>
> * CSS_KILL_ENQED, which will be set when css_killed_work_fn() is en-queued, and
> * CSS_REL_LATER, which, if set, will cause the css_release_work_fn() to be
> scheduled after the css_killed_work_fn is finished.
>
> There is also a new lock, which will protect the integrity of the css flags.
>
> [1] https://syzkaller.appspot.com/bug?id=e26e54d6eac9d9fb50b221ec3e4627b327465dbd
This also fixes a similar, cgroup related list corrupt issue:
https://syzkaller.appspot.com/bug?id=3c7ff113ccb695e839b859da3fc481c36eb1cfd5
--
Thanks,
Tadeusz
next prev parent reply other threads:[~2022-06-03 18:31 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-03 17:34 [PATCH] cgroup: serialize css kill and release paths Tadeusz Struk
2022-06-03 18:06 ` Tadeusz Struk
2022-06-03 18:13 ` [PATCH v2] " Tadeusz Struk
2022-06-03 18:17 ` Tadeusz Struk [this message]
2022-06-06 12:39 ` Michal Koutný
2022-06-07 18:47 ` Tadeusz Struk
2022-06-09 8:56 ` [cgroup] 3c87862ca1: WARNING:at_kernel/softirq.c:#__local_bh_enable_ip kernel test robot
2022-06-09 14:30 ` Tadeusz Struk
2022-06-09 14:55 ` Michal Koutný
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