linux-kernel - Re: Stricter module param and sysfs permission checks

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Message-ID: <87ob10vnp9.fsf@free.fr>
Date:	Thu, 20 Mar 2014 17:28:50 +0100
From:	Robert Jarzmik <robert.jarzmik@...e.fr>
To:	Dave Jones <davej@...hat.com>
Cc:	Rusty Russell <rusty@...tcorp.com.au>,
	Joe Perches <joe@...ches.com>, Theodore Ts'o <tytso@....edu>,
	Linux Kernel Developers List <linux-kernel@...r.kernel.org>,
	fes@...gle.com, Bjorn Helgaas <bhelgaas@...gle.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Alexey Dobriyan <adobriyan@...il.com>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	Simon Wood <simon@...gewell.org>
Subject: Re: Stricter module param and sysfs permission checks

Dave Jones <davej@...hat.com> writes:

> On Thu, Mar 20, 2014 at 01:43:44PM +1030, Rusty Russell wrote:
>
>  > drivers/mtd/devices/docg3.c:
>  >  	__ATTR(f##id##_dps0_protection_key, S_IWUGO, NULL, dps0_insert_key), \
>  > 	__ATTR(f##id##_dps1_protection_key, S_IWUGO, NULL, dps1_insert_key), \
>  > 
>  > drivers/scsi/pm8001/pm8001_ctl.c:
>  > static DEVICE_ATTR(update_fw, S_IRUGO|S_IWUGO,
>  > 	pm8001_show_update_fw, pm8001_store_update_fw);
>
> Why on earth are these world writable ?
For docg3, this attributes are used to input a "password" into the flash chip,
to unlock parts of the flash memory. By unlock I mean that a sector read will
return the actual sector when unlocked, and only 0xff if not read unlocked.

As to the "why writable" by "others", the legacy reason is that when I wrote
that code I had in mind that a casual user count :
 - input the code : "echo secret > dps0_protection_key"
 - mount /usermount

That's not a good reason, I know, and changing that to remove the "other" write
permission is fine by me.

Cheers.

-- 
Robert
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