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From: Denis Efremov <efremov@linux.com>
To: Julia Lawall <julia.lawall@inria.fr>
Cc: Joe Perches <joe@perches.com>,
	cocci@systeme.lip6.fr, linux-kernel@vger.kernel.org
Subject: Re: [Cocci] [PATCH 1/2] Coccinelle: extend memdup_user transformation with GFP_USER
Date: Sat, 6 Jun 2020 23:36:21 +0300	[thread overview]
Message-ID: <cc03afbe-2deb-e969-b2a3-e13242e904c6@linux.com> (raw)
In-Reply-To: <alpine.DEB.2.21.2006061024100.2578@hadrien>



On 6/6/20 11:24 AM, Julia Lawall wrote:
> 
> 
> On Sat, 30 May 2020, Denis Efremov wrote:
> 
>> Match GFP_USER allocations with memdup_user.cocci rule.
>> Commit 6c2c97a24f09 ("memdup_user(): switch to GFP_USER") switched
>> memdup_user() from GFP_KERNEL to GFP_USER. In most cases it is still
>> a good idea to use memdup_user() for GFP_KERNEL allocations. The
>> motivation behind altering memdup_user() to GFP_USER is here:
>> https://lkml.org/lkml/2018/1/6/333
> 
> Should the rule somehow document the cases in which memdup_user should now
> not be used?

As for now, I can't provide a counterexample. GPF_USER is more permissive than
GFP_KERNEL. It's completely ok to use GPF_USER with copy_from_user. Given that
memdup_user() was "silently" switched to GPF_USER from GPF_KERNEL with no callside
fixes, I think it's ok to recommend to use memdup_user for GPF_KERNEL matches with
no additional restrictions.

Thanks,
Denis

WARNING: multiple messages have this Message-ID (diff)
From: Denis Efremov <efremov@linux.com>
To: Julia Lawall <julia.lawall@inria.fr>
Cc: Joe Perches <joe@perches.com>,
	cocci@systeme.lip6.fr, linux-kernel@vger.kernel.org
Subject: Re: [Cocci] [PATCH 1/2] Coccinelle: extend memdup_user transformation with GFP_USER
Date: Sat, 6 Jun 2020 23:36:21 +0300	[thread overview]
Message-ID: <cc03afbe-2deb-e969-b2a3-e13242e904c6@linux.com> (raw)
In-Reply-To: <alpine.DEB.2.21.2006061024100.2578@hadrien>



On 6/6/20 11:24 AM, Julia Lawall wrote:
> 
> 
> On Sat, 30 May 2020, Denis Efremov wrote:
> 
>> Match GFP_USER allocations with memdup_user.cocci rule.
>> Commit 6c2c97a24f09 ("memdup_user(): switch to GFP_USER") switched
>> memdup_user() from GFP_KERNEL to GFP_USER. In most cases it is still
>> a good idea to use memdup_user() for GFP_KERNEL allocations. The
>> motivation behind altering memdup_user() to GFP_USER is here:
>> https://lkml.org/lkml/2018/1/6/333
> 
> Should the rule somehow document the cases in which memdup_user should now
> not be used?

As for now, I can't provide a counterexample. GPF_USER is more permissive than
GFP_KERNEL. It's completely ok to use GPF_USER with copy_from_user. Given that
memdup_user() was "silently" switched to GPF_USER from GPF_KERNEL with no callside
fixes, I think it's ok to recommend to use memdup_user for GPF_KERNEL matches with
no additional restrictions.

Thanks,
Denis
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  reply	other threads:[~2020-06-06 20:40 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-30 20:53 [PATCH 0/2] Update memdup_user.cocci Denis Efremov
2020-05-30 20:53 ` [Cocci] " Denis Efremov
2020-05-30 20:53 ` [PATCH 1/2] Coccinelle: extend memdup_user transformation with GFP_USER Denis Efremov
2020-05-30 20:53   ` [Cocci] " Denis Efremov
2020-06-02 13:24   ` Julia Lawall
2020-06-06  8:24   ` Julia Lawall
2020-06-06  8:24     ` Julia Lawall
2020-06-06 20:36     ` Denis Efremov [this message]
2020-06-06 20:36       ` Denis Efremov
2020-06-06 20:46     ` Denis Efremov
2020-06-06 20:46       ` Denis Efremov
2020-06-06 20:50       ` Julia Lawall
2020-06-06 20:50         ` Julia Lawall
2020-05-30 20:53 ` [PATCH 2/2] Coccinelle: extend memdup_user rule with vmemdup_user() Denis Efremov
2020-05-30 20:53   ` [Cocci] " Denis Efremov
2020-06-06  9:27   ` Julia Lawall
2020-06-06  9:27     ` Julia Lawall
2020-05-31 17:36 [Cocci] [PATCH 1/2] Coccinelle: extend memdup_user transformation with GFP_USER Markus Elfring

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