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Message-ID: <2bd7d03e-c2d0-0cb5-76fc-f5601324a18d@acm.org>
Date:   Mon, 13 Sep 2021 19:53:03 -0700
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Subject: Re: start switching sysfs attributes to expose the seq_file
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To:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc:     Christoph Hellwig <hch@lst.de>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Jens Axboe <axboe@kernel.dk>, Tejun Heo <tj@kernel.org>,
        linux-block@vger.kernel.org, linux-xfs@vger.kernel.org,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20210913054121.616001-1-hch@lst.de>
 <21413ac5-f934-efe2-25ee-115c4dcc86a5@acm.org> <YT+AbumufeL6nRss@kroah.com>
From:   Bart Van Assche <bvanassche@acm.org>
In-Reply-To: <YT+AbumufeL6nRss@kroah.com>
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On 9/13/21 09:46, Greg Kroah-Hartman wrote:
> On Mon, Sep 13, 2021 at 09:39:56AM -0700, Bart Van Assche wrote:
>> On 9/12/21 10:41 PM, Christoph Hellwig wrote:
>>> Al pointed out multiple times that seq_get_buf is highly dangerous as
>>> it opens up the tight seq_file abstractions to buffer overflows.  The
>>> last such caller now is sysfs.
>>>
>>> This series allows attributes to implement a seq_show method and switch
>>> the block and XFS code as users that I'm most familiar with to use
>>> seq_files directly after a few preparatory cleanups.  With this series
>>> "leaf" users of sysfs_ops can be converted one at at a time, after that
>>> we can move the seq_get_buf into the multiplexers (e.g. kobj, device,
>>> class attributes) and remove the show method in sysfs_ops and repeat the
>>> process until all attributes are converted.  This will probably take a
>>> fair amount of time.
>>
>> Hi Christoph,
>>
>> Thanks for having done this work. In case you would need it, some time ago
>> I posted the following sysfs patch but did not receive any feedback:
>> "[PATCH] kernfs: Improve lockdep annotation for files which implement mmap"
>> (https://lore.kernel.org/linux-kernel/20191004161124.111376-1-bvanassche@acm.org/).
>>
> 
> That was from back in 2019, sorry I must have missed it.
> 
> Care to rebase and resend it if it is still needed?

Hi Greg,

I think that patch is still relevant. It removes some ugly code from 
sysfs. I will rebase, retest and resend it.

Thanks,

Bart.