linux-kernel - Re: [PATCH] cifs: Add information about noserverino

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <4D0199E2.8030006@suse.de>
Date:	Fri, 10 Dec 2010 08:39:22 +0530
From:	Suresh Jayaraman <sjayaraman@...e.de>
To:	Jeff Layton <jlayton@...hat.com>
CC:	Steve French <smfrench@...il.com>,
	Bernhard Walle <bernhard@...lle.de>, sfrench@...ba.org,
	linux-cifs@...r.kernel.org, samba-technical@...ts.samba.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cifs: Add information about noserverino

On 12/10/2010 02:14 AM, Steve French wrote:
> On Thu, Dec 9, 2010 at 1:34 PM, Jeff Layton <jlayton@...hat.com> wrote:
>> On Thu, 9 Dec 2010 12:26:39 -0600
>> Steve French <smfrench@...il.com> wrote:
>>
>>> On Thu, Dec 9, 2010 at 6:09 AM, Jeff Layton <jlayton@...hat.com> wrote:
>>>> On Thu, 09 Dec 2010 17:10:28 +0530
>>>> Suresh Jayaraman <sjayaraman@...e.de> wrote:
>>>>
>>>>> On 12/06/2010 09:08 PM, Jeff Layton wrote:
>>>>>> On Mon, 06 Dec 2010 16:35:06 +0100
>>>>>> Bernhard Walle <bernhard@...lle.de> wrote:
>>>>>>
>>>>>>>
>>>>>>> Zitat von Jeff Layton <jlayton@...hat.com>:
>>>>>>>
>>>>>>>>
>>>>>>>> I'm still not sure I like this patch however. It potentially means a
>>>>>>>> lot of printk spam since these things have no ratelimiting. It also
>>>>>>>> doesn't tell me anything about which server might be giving me grief.
>>>>>>>>
>>>>>>>> Maybe this should be turned into a cFYI?
>>>>>>>
>>>>>>> Well, if I see it in the kernel log, it doesn't matter if it's info or
>>>>>>> something else.
>>>>>>>
>>>>>>>> The bottom line though is that running 32-bit applications that were
>>>>>>>> built without -D_FILE_OFFSET_BITS=64 on a 64-bit kernel is a very bad
>>>>>>>> idea. It would be nice to be able to alert users that things aren't
>>>>>>>> working the way they expect, but I'm not sure this is the right place
>>>>>>>> to do that.
>>>>>>>
>>>>>>> Well, but there *are* such application (in my case it was Softmaker Office
>>>>>>> which is a proprietary word processor) and it's quite nice if you know
>>>>>>> how you can workaround it when you encounter such a problem. That's all.
>>>>>>>
>>>>>>
>>>>>> Sure...but this problem is not limited to CIFS. Many modern filesystems
>>>>>> use 64-bit inodes. Running this application on XFS or NFS for instance
>>>>>> is likely to give you the same trouble. You just hit it on CIFS because
>>>>>> the server happened to give you a very large inode number.
>>>>>>
>>>>>> If we're going to add printk's for this situation, it probably ought to
>>>>>> be in a more generic place.
>>>>>>
>>>>>
>>>>> By generic place, did you mean at the VFS level? I think at VFS level,
>>>>> there is little information about the Server or underlying fs and this
>>>>> information doesn't seem too critical that VFS should warn/care much about.
>>>>>
>>>>> May be sticking to a cFYI along with Server detail is a good idea?
>>>>>
>>>> My poing was mainly that there's nothing special about CIFS in this
>>>> regard, other than the fact that servers regularly send us inodes that
>>>> are larger than 2^32. Why should we do this for cifs but not for nfs,
>>>> xfs, ext4, etc?
>>>>
>>>> The filldir function gets a dentry as an argument, so it could
>>>> reasonably generate a printk for this. I'm also not keen on
>>>> the printk recommending noserverino for this. That has its own
>>>> drawbacks.
>>>>
>>>> A cFYI for this sort of thing seems reasonable however.
>>>
>>> I agree that a cFYI is reasonable. �The next obvious question is: do
>>> we need to add code to generate unique 32 bit inode numbers
>>> that don't collide (as IIRC Samba does by xor the high and low 32
>>> bits of the inode number) when the app can't support ino64
>>> I would prefer not to go back to noserverino since that has worse
>>> drawbacks.
>>>
>>
>> Right, the fact that noserverino works around this is really just due
>> to an implementation detail of iunique(). That should probably be
>> discouraged as a solution since it's not guaranteed to be a workaround
>> in the future.
>>
>> If we did add such a switch, I'd suggest that we pattern it after what
>> NFS did for this. They added an "enable_ino64" module parameter a
>> couple of years ago that defaults to "true".

What are the advantages we have by making it a module parameter as
opposed to an mount option? XFS seems to have "inode64" mount option for
quite sometime now, without much issues..

> makes me uncomfortable to break ino64 for all mounts - when we
> may have one application on one mount that needs it (might be
> better to make a mount related)
> 
> 


-- 
Suresh Jayaraman
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/