linux-kernel - Re: [PATCH 15/16] COMPAT: add get/put_compat

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Message-ID: <4B445957.3040301@gmail.com>
Date:	Wed, 06 Jan 2010 10:35:19 +0100
From:	Jiri Slaby <jirislaby@...il.com>
To:	Arnd Bergmann <arnd@...db.de>
CC:	mingo@...e.hu, nhorman@...driver.com, sfr@...b.auug.org.au,
	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	marcin.slusarz@...il.com, tglx@...utronix.de, mingo@...hat.com,
	hpa@...or.com, torvalds@...ux-foundation.org,
	James Morris <jmorris@...ei.org>,
	Heiko Carstens <heiko.carstens@...ibm.com>
Subject: Re: [PATCH 15/16] COMPAT: add get/put_compat_rlimit

On 12/31/2009 12:55 AM, Arnd Bergmann wrote:
> On Wednesday 18 November 2009, Jiri Slaby wrote:
>>         set_fs(KERNEL_DS);
>> -       ret = sys_setrlimit(resource, (struct rlimit __user *) &r);
>> +       ret = sys_setrlimit(resource, (struct rlimit __force __user *)&r);
>>         set_fs(old_fs);
>>         return ret;
> 
> Since you are already rewriting the whole function here, it would be
> nice if you could just call do_setrlimit() with the kernel pointer
> instead of the set_fs() and __force tricks. For getrlimit, it may
> be easier to just open-code the whole function, and for your new
> functions, you could pass the pid into do_setrlimit instead of the
> task in order to reduce code duplication between compat_sys_setprlimit
> and sys_setprlimit.

Hmm, using pid_t wouldn't work well with pid namespaces. E.g. a call
from /proc code. But certainly some cleanups may be performed, at least
in {compat_,}sys_setrlimit case: pushing (resource >= RLIM_NLIMITS) test
down and calling do_setrlimit from compat_sys_setrlimit is
straightforward. Will look at the rest too.

> Yes, I realize my reply is late in this thread, but I assume your patch
> is still current since it hasn't made it into 2.6.33.

Yup, as you expressed, it's still not upstream, hence it can be tuned up
easily.

Thanks,
-- 
js
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