linux-kernel - Re: [PATCH 05/40] staging/lustre: validate open handle cookies

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Date:	Mon, 18 Nov 2013 10:36:26 +0800
From:	Peng Tao <bergwolf@...il.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	"Dilger, Andreas" <andreas.dilger@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Hammond, John" <john.hammond@...el.com>
Subject: Re: [PATCH 05/40] staging/lustre: validate open handle cookies

On Sun, Nov 17, 2013 at 3:50 AM, Greg Kroah-Hartman
<gregkh@...uxfoundation.org> wrote:
> On Sat, Nov 16, 2013 at 11:20:37AM +0000, Dilger, Andreas wrote:
>> On 2013/11/14 9:13 PM, "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>
>> wrote:
>>
>> >On Fri, Nov 15, 2013 at 12:13:07AM +0800, Peng Tao wrote:
>> >> From: "John L. Hammond" <john.hammond@...el.com>
>> >>
>> >> Add a const void *h_owner member to struct portals_handle. Add a const
>> >> void *owner parameter to class_handle2object() which must be matched
>> >> by the h_owner member of the handle in addition to the cookie.
>> >
>> >Ick ick ick.
>> >
>> >NEVER use a void pointer if you can help it, and for a "handle", never.
>> >This isn't other operating systems, sorry.  We know what types our
>> >pointers to structures are, use them, so that the compiler can catch our
>> >problems, and don't try to cheat by using void *.
>>
>> The portals_handle is used as a generic type for objects referenced over
>> the network, like a file handle.  The "owner" parameter is just used as
>> an extra check that the cookie passed from the client is actually a
>> valid value for the code in which it is being used (e.g. metadata or
>> data object).  It isn't actually dereferenced by anything, it is just
>> like a magic value.
>
> Then make it an explicit type, not a void *.
>
>> >> Adjust
>> >> the callers of class_handle2object() accordingly, using NULL as the
>> >> argument to the owner parameter, except in the case of
>> >> mdt_handle2mfd() where we add an explicit mdt_export_data parameter
>> >> which we use as the owner when searching for a MFD. When allocating a
>> >> new MFD, pass a pointer to the mdt_export_data into mdt_mfd_new() and
>> >> store it in h_owner. This allows the MDT to validate that the client
>> >> has not sent the wrong open handle cookie, or sent the right cookie to
>> >> the wrong MDT.
>> >
>> >This changelog entry doesn't even match up with the code below.  ALl
>> >callers of class_handle2object are passing NULL here, which makes this
>> >patch pretty pointless, right?
>>
>> As Tao wrote, this is the patch summary that matches what was committed
>> in our own tree and in this case mostly describes the changes made on the
>> server.  Keeping the same commits and comments in both trees makes it
>> easier to keep the code in sync.
>
> Ok, but as it is, this patch does nothing to the client code, so how can
> I accept it?  A function that is only ever called with NULL as an option
> is ripe for cleanup in my eyes.
>
How about adding a comment above the function to note that this extra
argument is used by server code and please don't remove it?

Thanks,
Tao
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