From: Oliver Hartkopp <socketcan@hartkopp•net>
To: Marek Vasut <marex@denx•de>, Marc Kleine-Budde <mkl@pengutronix•de>
Cc: linux-can@vger•kernel.org,
Wolfgang Grandegger <wg@grandegger•com>,
netdev@vger•kernel.org
Subject: Re: [PATCH] can: Use correct type in sizeof() in nla_put()
Date: Fri, 30 Oct 2015 15:53:31 +0100 [thread overview]
Message-ID: <5633846B.30107@hartkopp.net> (raw)
In-Reply-To: <201510301524.58411.marex@denx.de>
On 10/30/2015 03:24 PM, Marek Vasut wrote:
> On Friday, October 30, 2015 at 03:17:44 PM, Marc Kleine-Budde wrote:
>> On 10/30/2015 03:01 PM, Marek Vasut wrote:
>>> 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.
>
> In that case, yes, it's good. Hopefully, noone wrote his own thing.
>
Fortunately ip from iproute2 does it similary:
https://git.kernel.org/cgit/linux/kernel/git/shemminger/iproute2.git/tree/ip/iplink_can.c#n338
if (tb[IFLA_CAN_CLOCK]) {
struct can_clock *clock = RTA_DATA(tb[IFLA_CAN_CLOCK]);
fprintf(f, "\n clock %d", clock->freq);
}
As the clock is a read-only value kernel->userspace and nla_put creates its
own small ID/length information each time we are REALLY LUCKY that this fix
doesn't break the ABI in this case.
When can_clock would have been greater then can_ctrlmode we really had a
problem ...
Thanks for caching this!
Oliver
next prev parent reply other threads:[~2015-10-30 14:53 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-30 12:48 [PATCH] can: Use correct type in sizeof() in nla_put() Marek Vasut
2015-10-30 13:40 ` Marc Kleine-Budde
2015-10-30 14:01 ` Marek Vasut
2015-10-30 14:17 ` Marc Kleine-Budde
2015-10-30 14:24 ` Marek Vasut
2015-10-30 14:53 ` Oliver Hartkopp [this message]
2015-10-30 15:33 ` Marek Vasut
-- strict thread matches above, loose matches on Subject: below --
2015-10-30 13:39 pull-request: can 2015-10-30 Marc Kleine-Budde
2015-10-30 13:39 ` [PATCH] can: Use correct type in sizeof() in nla_put() Marc Kleine-Budde
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=5633846B.30107@hartkopp.net \
--to=socketcan@hartkopp$(echo .)net \
--cc=linux-can@vger$(echo .)kernel.org \
--cc=marex@denx$(echo .)de \
--cc=mkl@pengutronix$(echo .)de \
--cc=netdev@vger$(echo .)kernel.org \
--cc=wg@grandegger$(echo .)com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox