linux-kernel - Re: [PATCH 28/49] tty: Add a new file /proc/tty/consoles

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Message-ID: <4CC2CE66.7010405@suse.cz>
Date:	Sat, 23 Oct 2010 14:00:38 +0200
From:	Jiri Slaby <jslaby@...e.cz>
To:	Al Viro <viro@...IV.linux.org.uk>
CC:	Greg Kroah-Hartman <gregkh@...e.de>, linux-kernel@...r.kernel.org,
	"Dr. Werner Fink" <werner@...e.de>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 28/49] tty: Add a new file /proc/tty/consoles

On 10/23/2010 01:51 PM, Al Viro wrote:
> On Sat, Oct 23, 2010 at 01:40:24PM +0200, Jiri Slaby wrote:
>> On 10/22/2010 08:21 PM, Greg Kroah-Hartman wrote:
>>> +/*
>>> + * Used for open /proc/tty/consoles. Before this detect
>>> + * the device ID of file descriptor 0 of the current
>>> + * reading task if a character device...
>>> + */
>>> +static int tty_consoles_open(struct inode *inode, struct file *file)
>>> +{
>>> +	struct files_struct *curfiles;
>>> +
>>> +	current_dev = 0;
>>> +	curfiles = get_files_struct(current);
>>> +	if (curfiles) {
>>> +		const struct file *curfp;
>>> +		spin_lock(&curfiles->file_lock);
>>> +		curfp = fcheck_files(curfiles, 0);
>>> +		if (curfp && curfp->private_data) {
>>> +			const struct inode *inode;
>>> +			dget(curfp->f_dentry);
>>> +			inode = curfp->f_dentry->d_inode;
>>> +			if (S_ISCHR(inode->i_mode)) {
>>> +				struct tty_struct *tty;
>>> +				tty = (struct tty_struct *)curfp->private_data;
>>> +				if (tty && tty->magic == TTY_MAGIC) {
>>
>> Ah, I've just understood what this code does. It seems, that the 'tty'
>> at this point may be already freed (e.g. people don't set private_data
>> to NULL). Please explain in the code why it can't...
> 
> Please, don't.  Even leaving aside the fact that it's mind-bogglingly
> broken (->private_data can be _ANYTHING_, including arbitrary number cast
> to pointer), you really shouldn't screw your way through the descriptor
> table in the first place.
> 
> Strongly NACKed.

Well, our complains are -ETOOLATE -- it's commit f4a3e0bceb57466c
upstream. So please fix this up.

regards,
-- 
js
suse labs
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