linux-kernel - Re: [PATCH] mmc: block: Add new ioctl to send multi commands

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Thu, 10 Sep 2015 10:10:52 -0700
From:	Grant Grundler <grundler@...gle.com>
To:	Jon Hunter <jonathanh@...dia.com>
Cc:	Arnd Bergmann <arnd@...db.de>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Olof Johansson <olofj@...omium.org>,
	Seshagiri Holi <sholi@...dia.com>,
	"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mmc: block: Add new ioctl to send multi commands

On Thu, Sep 10, 2015 at 1:24 AM, Jon Hunter <jonathanh@...dia.com> wrote:
...
>> - you have some implicit padding after the structure and should replace that
>>   with explictit pad bytes to extend the structure to a multiple of its
>>   alignment (8 bytes).
>
> Would padding with __u32 at the end be sufficient here? I assume the
> __u32 would be 32-bit aligned. However, was not sure if this would
> always be the case.

Is there something wrong with implicit padding?
Only one copy of the structure is passed to the kernel for any given call.

>>>> struct mmc_ioc_multi_cmd {
>>>>     __u64 num_of_cmds;
>>>>     struct mmc_ioc_cmd cmds[0];
>>>> };

I think this would work just as well. But doesn't "pointer to an
array" require 32-bit ioctl compat handling?
We were trying to avoid a 32-bit user space compatibility handler.

>>>> as I said, both are ugly. My first choice would have been the other one,
>>>> but I'm sure you have some reasons yourself.

Why do you prefer the alternative you proposed?

My guess is better type checking (and I would like that too). But
maybe there is something else?

cheers,
grant
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/