From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail144.messagelabs.com (mail144.messagelabs.com [216.82.254.51]) by kanga.kvack.org (Postfix) with SMTP id DE1896B00B4 for ; Sun, 8 Mar 2009 22:22:10 -0400 (EDT) Message-ID: <49B47D50.5000608@cn.fujitsu.com> Date: Mon, 09 Mar 2009 10:22:08 +0800 From: Li Zefan MIME-Version: 1.0 Subject: Re: [PATCH -v2] memdup_user(): introduce References: <49B0CAEC.80801@cn.fujitsu.com> <20090306082056.GB3450@x200.localdomain> <49B0DE89.9000401@cn.fujitsu.com> <20090306003900.a031a914.akpm@linux-foundation.org> <49B0E67C.2090404@cn.fujitsu.com> <20090306011548.ffdf9cbc.akpm@linux-foundation.org> <49B0F1B9.1080903@cn.fujitsu.com> <20090306150335.c512c1b6.akpm@linux-foundation.org> <20090307084805.7cf3d574@infradead.org> In-Reply-To: <20090307084805.7cf3d574@infradead.org> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Arjan van de Ven Cc: Andrew Morton , adobriyan@gmail.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: >>> +EXPORT_SYMBOL(memdup_user); > > Hi, > > I like the general idea of this a lot; it will make things much less > error prone (and we can add some sanity checks on "len" to catch the > standard security holes around copy_from_user usage). I'd even also > want a memdup_array() like thing in the style of calloc(). > > However, I have two questions/suggestions for improvement: > > I would like to question the use of the gfp argument here; > copy_from_user sleeps, so you can't use GFP_ATOMIC anyway. > You can't use GFP_NOFS etc, because the pagefault path will happily do > things that are equivalent, if not identical, to GFP_KERNEL. > > So the only value you can pass in correctly, as far as I can see, is > GFP_KERNEL. Am I wrong? > Right! I just dug and found a few kmalloc(GFP_ATOMIC/GFP_NOFS)+copy_from_user(), so we have one more reason to use this memdup_user(). -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org