linux-kernel - Re: [PATCH] 9p: fix NULL pointer dereferences

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Message-ID: <CACT4Y+Zk_d_Ea-oM0R4cRsdnXogq4S+MZMLHJiJuYzibUkanfA@mail.gmail.com>
Date:   Thu, 26 Jul 2018 11:54:39 +0200
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Dominique Martinet <asmadeus@...ewreck.org>
Cc:     Tomas Bortoli <tomasbortoli@...il.com>,
        David Miller <davem@...emloft.net>,
        v9fs-developer@...ts.sourceforge.net,
        netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        syzkaller <syzkaller@...glegroups.com>
Subject: Re: [PATCH] 9p: fix NULL pointer dereferences

On Thu, Jul 26, 2018 at 11:48 AM, Dominique Martinet
<asmadeus@...ewreck.org> wrote:
> Dmitry Vyukov wrote on Thu, Jul 26, 2018:
>> > Let's refuse that at much higher level, like v9fs_mount() in
>> > fs/9p/vfs_super.c
>> >
>> > I can't think of any valid reason for dev_name to be NULL, it's the
>> > target IP or virtio handle.
>>
>> But I think trans=fd allows NULL addr today, no?
>
> Ah, right, I read the patch too fast and read unix_create as fd_create,
> I never realized there was a unix_create variant...
>
> fd legitimately doesn't need a name, you are correct.
>
> I'm really curious if anyone ever uses the unix/fd variants for "real"
> stuff though! (not meaning syzbot isn't real, but I have yet to see
> anything take advantage of this, even if I could imagine some fun
> applications by piping the wmii libixp server socket.. and just crashed
> my laptop trying because of the (fixed) trans put bug.. I have yet to
> see anyone actually doing this)

I don't really know any real-world cases, but 9p over fd it looks like
a kind of fuse, so perhaps somebody uses it this way.
Also, fd allows to use something like sctp socket, and if I am not
mistaken, trans=tcp can't even do ipv6 tcp (?).


> On the other hand, virtio, rdma and xen all have the same problem, so
> Thomas, please fix them instead :)