netdev - Re: [Patch net v2] cgroup: fix cgroup_sk_alloc() for sk_clone

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Message-ID: <CAM_iQpWaWcJYG_JWkHdy__=Y5NYPFaX2T+W-c6MskYoZ8G7rRQ@mail.gmail.com>
Date:   Thu, 9 Jul 2020 11:59:09 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Cameron Berkenpas <cam@...-zeon.de>,
        Peter Geis <pgwipeout@...il.com>,
        Lu Fengqi <lufq.fnst@...fujitsu.com>,
        Daniël Sonck <dsonck92@...il.com>,
        Zhang Qiang <qiang.zhang@...driver.com>,
        Thomas Lamprecht <t.lamprecht@...xmox.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Zefan Li <lizefan@...wei.com>, Tejun Heo <tj@...nel.org>,
        Roman Gushchin <guro@...com>
Subject: Re: [Patch net v2] cgroup: fix cgroup_sk_alloc() for sk_clone_lock()

On Thu, Jul 9, 2020 at 11:51 AM Cong Wang <xiyou.wangcong@...il.com> wrote:
>
> On Thu, Jul 9, 2020 at 10:10 AM Guenter Roeck <linux@...ck-us.net> wrote:
> >
> > Something seems fishy with the use of skcd->val on big endian systems.
> >
> > Some debug output:
> >
> > [   22.643703] sock: ##### sk_alloc(sk=000000001be28100): Calling cgroup_sk_alloc(000000001be28550)
> > [   22.643807] cgroup: ##### cgroup_sk_alloc(skcd=000000001be28550): cgroup_sk_alloc_disabled=0, in_interrupt: 0
> > [   22.643886] cgroup:  #### cgroup_sk_alloc(skcd=000000001be28550): cset->dfl_cgrp=0000000001224040, skcd->val=0x1224040
> > [   22.643957] cgroup: ###### cgroup_bpf_get(cgrp=0000000001224040)
> > [   22.646451] sock: ##### sk_prot_free(sk=000000001be28100): Calling cgroup_sk_free(000000001be28550)
> > [   22.646607] cgroup:  #### sock_cgroup_ptr(skcd=000000001be28550) -> 0000000000014040 [v=14040, skcd->val=14040]
> > [   22.646632] cgroup: ####### cgroup_sk_free(): skcd=000000001be28550, cgrp=0000000000014040
> > [   22.646739] cgroup: ####### cgroup_sk_free(): skcd->no_refcnt=0
> > [   22.646814] cgroup: ####### cgroup_sk_free(): Calling cgroup_bpf_put(cgrp=0000000000014040)
> > [   22.646886] cgroup: ###### cgroup_bpf_put(cgrp=0000000000014040)
>
> Excellent debugging! I thought it was a double put, but it seems to
> be an endian issue. I didn't realize the bit endian machine actually
> packs bitfields in a big endian way too...
>
> Does the attached patch address this?

Ah, this is too ugly. We just have to always make them the last two bits.

Please test this attached patch instead and ignore the previous one.

Thanks.

View attachment "sock_cgroup_ptr.diff" of type "text/x-patch" (516 bytes)