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Date: Fri, 3 Jan 2020 09:47:01 -0800 From: Song Liu <liu.song.a23@...il.com> To: Roman Gushchin <guro@...com> Cc: bpf <bpf@...r.kernel.org>, Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, open list <linux-kernel@...r.kernel.org>, Kernel Team <kernel-team@...com>, Networking <netdev@...r.kernel.org>, stable@...r.kernel.org Subject: Re: [PATCH bpf] bpf: cgroup: prevent out-of-order release of cgroup bpf On Fri, Dec 27, 2019 at 1:50 PM Roman Gushchin <guro@...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@...icpanda.com> > Signed-off-by: Roman Gushchin <guro@...com> > Cc: Alexei Starovoitov <ast@...nel.org> > Cc: stable@...r.kernel.org LGTM. Thanks for the fix! Acked-by: Song Liu <songliubraving@...com>
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