netdev - Re: [PATCH bpf] bpf: Fix cgroup local storage prog tracking

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Message-ID: <20191217181356.GA5770@localhost.localdomain>
Date:   Tue, 17 Dec 2019 18:14:00 +0000
From:   Roman Gushchin <guro@...com>
To:     Daniel Borkmann <daniel@...earbox.net>
CC:     "ast@...nel.org" <ast@...nel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        "Martin Lau" <kafai@...com>
Subject: Re: [PATCH bpf] bpf: Fix cgroup local storage prog tracking

On Tue, Dec 17, 2019 at 01:28:16PM +0100, Daniel Borkmann wrote:
> Recently noticed that we're tracking programs related to local storage maps
> through their prog pointer. This is a wrong assumption since the prog pointer
> can still change throughout the verification process, for example, whenever
> bpf_patch_insn_single() is called.

Oh, I didn't know it.

> 
> Therefore, the prog pointer that was assigned via bpf_cgroup_storage_assign()
> is not guaranteed to be the same as we pass in bpf_cgroup_storage_release()
> and the map would therefore remain in busy state forever. Fix this by using
> the prog's aux pointer which is stable throughout verification and beyond.
> 
> Fixes: de9cbbaadba5 ("bpf: introduce cgroup storage maps")
> Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
> Cc: Roman Gushchin <guro@...com>
> Cc: Martin KaFai Lau <kafai@...com>

Acked-by: Roman Gushchin <guro@...com>

Thank you, Daniel!