Re: [PATCH] mtd: require write permissions for locking and badblock ioctls

From: Richard Weinberger <richard@nod.at>
To: Michael Walle <michael@walle.cc>
Cc: linux-mtd <linux-mtd@lists.infradead.org>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	Miquel Raynal <miquel.raynal@bootlin.com>,
	Vignesh Raghavendra <vigneshr@ti.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Subject: Re: [PATCH] mtd: require write permissions for locking and badblock ioctls
Date: Wed, 3 Mar 2021 17:17:16 +0100 (CET)	[thread overview]
Message-ID: <689194005.42755.1614788236355.JavaMail.zimbra@nod.at> (raw)
In-Reply-To: <YD+0mAPTMN8AwNBx@kroah.com>

Michael,

----- Ursprüngliche Mail -----
> Von: "Greg Kroah-Hartman" <gregkh@linuxfoundation.org>
> An: "Michael Walle" <michael@walle.cc>
> CC: "linux-mtd" <linux-mtd@lists.infradead.org>, "linux-kernel" <linux-kernel@vger.kernel.org>, "Miquel Raynal"
> <miquel.raynal@bootlin.com>, "richard" <richard@nod.at>, "Vignesh Raghavendra" <vigneshr@ti.com>
> Gesendet: Mittwoch, 3. März 2021 17:08:56
> Betreff: Re: [PATCH] mtd: require write permissions for locking and badblock ioctls

> On Wed, Mar 03, 2021 at 04:57:35PM +0100, Michael Walle wrote:
>> MEMLOCK, MEMUNLOCK and OTPLOCK modify protection bits. Thus require
>> write permission. Depending on the hardware MEMLOCK might even be
>> write-once, e.g. for SPI-NOR flashes with their WP# tied to GND. OTPLOCK
>> is always write-once.
>> 
>> MEMSETBADBLOCK modifies the bad block table.
>> 
>> Fixes: f7e6b19bc764 ("mtd: properly check all write ioctls for permissions")
>> Signed-off-by: Michael Walle <michael@walle.cc>
>> ---
>>  drivers/mtd/mtdchar.c | 8 ++++----
>>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> Thanks for auditing the rest of these from my original patch.  If this
> is ok with userspace tools, it's fine with me, but I don't even have
> this hardware to test with :)

That's my fear. Michael, did you verify?
In general you need to be root to open these device files.
So, I don't see a security problem here.

Thanks,
//richard