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From: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
To: Greg KH <gregkh@linuxfoundation.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Minchan Kim <minchan@kernel.org>,
	Steven Allen <steven@stebalien.com>,
	linux-kernel@vger.kernel.org, stable@vger.kernel.org,
	Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Subject: Re: [PATCH] zram: restrict add/remove attributes to root only
Date: Sun, 4 Dec 2016 19:52:08 +0900	[thread overview]
Message-ID: <20161204105208.GA592@tigerII.localdomain> (raw)
In-Reply-To: <20161204102807.GB15437@kroah.com>

On (12/04/16 11:28), Greg KH wrote:
> On Sun, Dec 04, 2016 at 11:35:15AM +0900, Sergey Senozhatsky wrote:
[..]

> Why can't a normal user read the attribute?  Does a read actually modify
> something?

yes, it does.

reading from a hot_add file creates a new zram device and returns a new
device's device_id. not initialized device (so it does not eat the memory
for handle table, etc.), but with its own set of sysfs attrs, etc. which
consumes memory after all. so a 'normal' user, doing a simple read from a
hot_add file in a loop just for fun, can create a lot of devices and,
quite likely, cause some troubles (as reported by Steven Allen).

	-ss

  reply	other threads:[~2016-12-04 10:53 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-12-04  2:35 [PATCH] zram: restrict add/remove attributes to root only Sergey Senozhatsky
2016-12-04 10:28 ` Greg KH
2016-12-04 10:52   ` Sergey Senozhatsky [this message]
2016-12-04 11:28     ` Greg KH
2016-12-04 11:41       ` Sergey Senozhatsky
2016-12-04 11:55         ` Greg KH
2016-12-04 12:08           ` Sergey Senozhatsky
2016-12-04 12:49       ` Sergey Senozhatsky

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