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

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Date:   Wed, 8 Aug 2018 17:51:34 +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 Fri, Jul 27, 2018 at 12:15 AM, Dominique Martinet
<asmadeus@...ewreck.org> wrote:
> Tomas Bortoli wrote on Thu, Jul 26, 2018:
>> > If we want to preserve the current behaviour for trans=fd (and I don't
>> > see why not) we just have to patch all the transports that use the
>> > device, that is all .create functions but p9_fd_create()
>> >
>> > Basically exactly what you did, just for a few more functions - I
>> > apparently was a little bit too optimistic thinking we could share
>> > this check.
>>
>> Does v9fs_mount() knows the transport ahead? Because in that case it'd
>> be possible to check if addr!=NULL && trans!=fd then return error
>>
>> Otherwise, patching all the .create, ok.
>
> 9p option parsing is all over the place, split in fs/9p/v9fs,
> net/9p/client and net/9p/trans_*... Which is actually somewhat of a
> problem because that means we can't warn on unused option as each parser
> does not know the full subset of options used, so if someone makes a
> typo they're on their own to figure it out :/
>
>
> If you want to factor it in, v9fs_mount does not know which transport is
> used, but p9_client_create does know - although the functions/structs
> are all static so you need to check clnt->trans_mod->name with strcmp
> and I'm honestly not sure that's better than checking in each function..
>
> But, as usual I'm happy as long as it works, so pick your poison :)

So let's proceed with checking in each transport function?