Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761283Ab0GTMkF (ORCPT ); Tue, 20 Jul 2010 08:40:05 -0400 Received: from sm-d311v.smileserver.ne.jp ([203.211.202.206]:38821 "EHLO sm-d311v.smileserver.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756581Ab0GTMkE (ORCPT ); Tue, 20 Jul 2010 08:40:04 -0400 Message-ID: <000d01cb2808$ac78d300$66f8800a@maildom.okisemi.com> From: "Masayuki Ohtake" To: "Arnd Bergmann" Cc: , , "Wang, Yong Y" , , "LKML" , , "Ben Dooks \(embedded platforms\)" , "Jean Delvare \(PC drivers, core\)" References: <4C204B0D.2030201@dsn.okisemi.com> <201007152135.00280.arnd@arndb.de> <000601cb27e4$3768c170$66f8800a@maildom.okisemi.com> <201007201129.53110.arnd@arndb.de> Subject: Re: [PATCH] I2C driver of Topcliff PCH Date: Tue, 20 Jul 2010 21:40:00 +0900 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1983 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1983 X-Hosting-Pf: 0 X-NAI-Spam-Score: 1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1955 Lines: 52 Hi Arnd, > That is a highly unusual interface and I would definitely not recommend doing > this. Please use an ioctl operation for anything that has both input and output > data. I will delete the special interface from our i2c driver. Thanks, Ohtake ----- Original Message ----- From: "Arnd Bergmann" To: "Masayuki Ohtake" Cc: ; ; "Wang, Yong Y" ; ; "LKML" ; ; "Ben Dooks (embedded platforms)" ; "Jean Delvare (PC drivers, core)" Sent: Tuesday, July 20, 2010 6:29 PM Subject: Re: [PATCH] I2C driver of Topcliff PCH > On Tuesday 20 July 2010, Masayuki Ohtake wrote: > > > > @@ -147,6 +148,11 @@ static ssize_t i2cdev_read(struct file *file, char __user *buf, size_t count, > > > > if (tmp == NULL) > > > > return -ENOMEM; > > > > > > > > + if (copy_from_user(tmp, buf, count)) { > > > > + kfree(tmp); > > > > + return -EFAULT; > > > > + } > > > > + > > > > pr_debug("i2c-dev: i2c-%d reading %zu bytes.\n", > > > > iminor(file->f_path.dentry->d_inode), count); > > > > > > > > > A read function should not do copy_from_user, only copy_to_user. > > > If you are worried about returning invalid data from kernel space, > > > better use kzalloc instead of kmalloc to get the buffer. > > > > Our I2C HW has special mode. > > To control the mode, our i2c driver has copy_from_user. > > That is a highly unusual interface and I would definitely not recommend doing > this. Please use an ioctl operation for anything that has both input and output > data. > > Arnd > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/