linux-kernel - Re: [PATCH] Change paride driver to use unlocked

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Date:	Wed, 9 Jan 2008 13:14:25 +0100 (CET)
From:	Jan Engelhardt <jengelh@...putergmbh.de>
To:	Nikanth Karthikesan <knikanth@...e.de>
cc:	grant@...que.net, tim@...erelk.net,
	Christoph Hellwig <hch@...radead.org>, Valdis.Kletnieks@...edu,
	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] Change paride driver to use unlocked_ioctl instead of
 ioctl


On Jan 10 2008 14:25, Nikanth Karthikesan wrote:
>-static int pt_ioctl(struct inode *inode, struct file *file,
>-	 unsigned int cmd, unsigned long arg)
>+static long pt_ioctl(struct file *file, unsigned int cmd,
>+		unsigned long arg)
> {
> 	struct pt_unit *tape = file->private_data;
> 	struct mtop __user *p = (void __user *)arg;
> 	struct mtop mtop;
>+	long err = 0;
>+
>+	lock_kernel();
> 
> 	switch (cmd) {
> 	case MTIOCTOP:
>-		if (copy_from_user(&mtop, p, sizeof(struct mtop)))
>-			return -EFAULT;
>+		if (copy_from_user(&mtop, p, sizeof(struct mtop))) {
>+			err = -EFAULT;
>+			break;
>+		}

I wonder why a simple copy_from_user() requires the BKL.. if pt
does need locking, then probably some mutex inside pt.

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