netdev - Re: [PATCH] can: Use correct type in sizeof() in nla

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Date:	Fri, 30 Oct 2015 15:17:44 +0100
From:	Marc Kleine-Budde <mkl@...gutronix.de>
To:	Marek Vasut <marex@...x.de>
Cc:	linux-can@...r.kernel.org, Wolfgang Grandegger <wg@...ndegger.com>,
	netdev@...r.kernel.org
Subject: Re: [PATCH] can: Use correct type in sizeof() in nla_put()

On 10/30/2015 03:01 PM, Marek Vasut wrote:
> On Friday, October 30, 2015 at 02:40:26 PM, Marc Kleine-Budde wrote:
>> On 10/30/2015 01:48 PM, Marek Vasut wrote:
>>> The sizeof() is invoked on an incorrect variable, likely due to some
>>> copy-paste error, and this might result in memory corruption. Fix this.
>>>
>>> Signed-off-by: Marek Vasut <marex@...x.de>
>>> Cc: Wolfgang Grandegger <wg@...ndegger.com>
>>> Cc: Marc Kleine-Budde <mkl@...gutronix.de>
>>> Cc: netdev@...r.kernel.org
>>
>> Applies to can and added stable on Cc.
> 
> Are you absolutelly positive this doesn't break kernel ABI please ?
> 
> I am a little worried there, since the size of can_clock and can_ctrlmode
> structures differ.

struct can_clock is a u32, see [1]
struct can_ctrlmode is 2 x u32.

in libsocketcan[2] it's accessed like this:

> 	memcpy(res,
> 		RTA_DATA(can_attr[IFLA_CAN_CLOCK]),
> 		sizeof(struct can_clock));

I think it should be ok.

Marc

[1]
http://lxr.free-electrons.com/source/include/uapi/linux/can/netlink.h#L61
[2]
http://git.pengutronix.de/?p=tools/libsocketcan.git;a=blob;f=src/libsocketcan.c;h=c97a28cca18054c8e63326eeb5a866b79344ebe2;hb=4ea9ec7cf37a0c52f2c39a13887aaad11042ef5c#l453

-- 
Pengutronix e.K.                  | Marc Kleine-Budde           |
Industrial Linux Solutions        | Phone: +49-231-2826-924     |
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