netdev - Re: [PATCH bpf] bpf: fix wrong helper enablement in cgroup local storage

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Date:   Fri, 26 Oct 2018 16:05:17 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Roman Gushchin <guro@...com>
Cc:     Daniel Borkmann <daniel@...earbox.net>,
        "ast@...nel.org" <ast@...nel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH bpf] bpf: fix wrong helper enablement in cgroup local
 storage

On Fri, Oct 26, 2018 at 10:57:18PM +0000, Roman Gushchin wrote:
> On Sat, Oct 27, 2018 at 12:49:02AM +0200, Daniel Borkmann wrote:
> > Commit cd3394317653 ("bpf: introduce the bpf_get_local_storage()
> > helper function") enabled the bpf_get_local_storage() helper also
> > for BPF program types where it does not make sense to use them.
> > 
> > They have been added both in sk_skb_func_proto() and sk_msg_func_proto()
> > even though both program types are not invoked in combination with
> > cgroups, and neither through BPF_PROG_RUN_ARRAY(). In the latter the
> > bpf_cgroup_storage_set() is set shortly before BPF program invocation.
> > 
> > Later, the helper bpf_get_local_storage() retrieves this prior set
> > up per-cpu pointer and hands the buffer to the BPF program. The map
> > argument in there solely retrieves the enum bpf_cgroup_storage_type
> > from a local storage map associated with the program and based on the
> > type returns either the global or per-cpu storage. However, there
> > is no specific association between the program's map and the actual
> > content in bpf_cgroup_storage[].
> > 
> > Meaning, any BPF program that would have been properly run from the
> > cgroup side through BPF_PROG_RUN_ARRAY() where bpf_cgroup_storage_set()
> > was performed, and that is later unloaded such that prog / maps are
> > teared down will cause a use after free if that pointer is retrieved
> > from programs that are not run through BPF_PROG_RUN_ARRAY() but have
> > the cgroup local storage helper enabled in their func proto.
> > 
> > Lets just remove it from the two sock_map program types to fix it.
> > Auditing through the types where this helper is enabled, it appears
> > that these are the only ones where it was mistakenly allowed.
> > 
> > Fixes: cd3394317653 ("bpf: introduce the bpf_get_local_storage() helper function")
> > Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
> > Cc: Roman Gushchin <guro@...com>
> > Acked-by: John Fastabend <john.fastabend@...il.com>
> 
> 
> Acked-by: Roman Gushchin <guro@...com>

Applied, Thanks