From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with ESMTP id E872F6B0062 for ; Fri, 6 Mar 2009 18:04:15 -0500 (EST) Date: Fri, 6 Mar 2009 15:03:35 -0800 From: Andrew Morton Subject: Re: [PATCH -v2] memdup_user(): introduce Message-Id: <20090306150335.c512c1b6.akpm@linux-foundation.org> In-Reply-To: <49B0F1B9.1080903@cn.fujitsu.com> 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> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Li Zefan Cc: adobriyan@gmail.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: On Fri, 06 Mar 2009 17:49:45 +0800 Li Zefan wrote: > I notice there are many places doing copy_from_user() which follows > kmalloc(): > > dst = kmalloc(len, GFP_KERNEL); > if (!dst) > return -ENOMEM; > if (copy_from_user(dst, src, len)) { > kfree(dst); > return -EFAULT > } > > memdup_user() is a wrapper of the above code. With this new function, > we don't have to write 'len' twice, which can lead to typos/mistakes. > It also produces smaller code and kernel text. > > A quick grep shows 250+ places where memdup_user() *may* be used. I'll > prepare a patchset to do this conversion. > > v1 -> v2: change the name from kmemdup_from_user to memdup_user. > > Signed-off-by: Li Zefan > --- > > Can this get into 2.6.29, so I can prepare patches based on linux-next? > And this won't cause regression, since no one uses it yet. :) I'd be OK with doing that from a patch logistics point of view, but I'd prefer to leave a patch like this for a few days to gather more feedback from other developers, which might push this into 2.6.30. > diff --git a/include/linux/string.h b/include/linux/string.h > index 76ec218..79f30f3 100644 > --- a/include/linux/string.h > +++ b/include/linux/string.h > @@ -12,6 +12,7 @@ > #include /* for NULL */ > > extern char *strndup_user(const char __user *, long); > +extern void *memdup_user(const void __user *, size_t, gfp_t); > > /* > * Include machine specific inline routines > diff --git a/mm/util.c b/mm/util.c > index 37eaccd..3d21c21 100644 > --- a/mm/util.c > +++ b/mm/util.c > @@ -70,6 +70,32 @@ void *kmemdup(const void *src, size_t len, gfp_t gfp) > EXPORT_SYMBOL(kmemdup); > > /** > + * memdup_user - duplicate memory region from user space > + * > + * @src: source address in user space > + * @len: number of bytes to copy > + * @gfp: GFP mask to use > + * > + * Returns an ERR_PTR() on failure. > + */ > +void *memdup_user(const void __user *src, size_t len, gfp_t gfp) > +{ > + void *p; > + > + p = kmalloc_track_caller(len, gfp); > + if (!p) > + return ERR_PTR(-ENOMEM); > + > + if (copy_from_user(p, src, len)) { > + kfree(p); > + return ERR_PTR(-EFAULT); > + } > + > + return p; > +} > +EXPORT_SYMBOL(memdup_user); > + > +/** > * __krealloc - like krealloc() but don't free @p. > * @p: object to reallocate memory for. > * @new_size: how many bytes of memory are required. > -- > 1.5.4.rc3 -- 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