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From: Song Liu <liu.song.a23@gmail.com>
To: Roman Gushchin <guro@fb.com>
Cc: bpf <bpf@vger.kernel.org>, Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	open list <linux-kernel@vger.kernel.org>,
	Kernel Team <kernel-team@fb.com>,
	Networking <netdev@vger.kernel.org>,
	stable@vger.kernel.org
Subject: Re: [PATCH bpf] bpf: cgroup: prevent out-of-order release of cgroup bpf
Date: Fri, 3 Jan 2020 09:47:01 -0800	[thread overview]
Message-ID: <CAPhsuW7SKrS9WOVZXXoXjeGaFugUZmwip-m44gWAWyCbEkhBvA@mail.gmail.com> (raw)
In-Reply-To: <20191227215034.3169624-1-guro@fb.com>

On Fri, Dec 27, 2019 at 1:50 PM Roman Gushchin <guro@fb.com> wrote:
>
> Before commit 4bfc0bb2c60e ("bpf: decouple the lifetime of cgroup_bpf
> from cgroup itself") cgroup bpf structures were released with
> corresponding cgroup structures. It guaranteed the hierarchical order
> of destruction: children were always first. It preserved attached
> programs from being released before their propagated copies.
>
> But with cgroup auto-detachment there are no such guarantees anymore:
> cgroup bpf is released as soon as the cgroup is offline and there are
> no live associated sockets. It means that an attached program can be
> detached and released, while its propagated copy is still living
> in the cgroup subtree. This will obviously lead to an use-after-free
> bug.
>
[...]
>
> Thanks to Josef Bacik for the debugging and the initial analysis of
> the problem.
>
> Fixes: 4bfc0bb2c60e ("bpf: decouple the lifetime of cgroup_bpf from cgroup itself")
> Reported-by: Josef Bacik <josef@toxicpanda.com>
> Signed-off-by: Roman Gushchin <guro@fb.com>
> Cc: Alexei Starovoitov <ast@kernel.org>
> Cc: stable@vger.kernel.org

LGTM. Thanks for the fix!

Acked-by: Song Liu <songliubraving@fb.com>

  parent reply	other threads:[~2020-01-03 17:47 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-27 21:50 Roman Gushchin
2020-01-03 15:30 ` Roman Gushchin
2020-01-03 17:47 ` Song Liu [this message]
2020-01-04  0:35 ` Alexei Starovoitov
2020-01-04  1:13   ` Roman Gushchin
2020-01-04  2:31     ` Alexei Starovoitov
2020-01-04  3:00       ` Roman Gushchin
2020-01-06 22:07         ` Alexei Starovoitov
2020-01-06 22:20           ` Roman Gushchin

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