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

[Jiri Slaby]

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...

Maybe I wouldn't bother with marking the "current" console by star at
all as it seems not to pay off.

> +					tty = tty_pair_get_tty(tty);
> +					current_dev = tty_devnum(tty);
> +				}
> +			}
> +			dput(curfp->f_dentry);
> +		}
> +		spin_unlock(&curfiles->file_lock);
> +		put_files_struct(curfiles);
> +	}
> +	return seq_open(file, &tty_consoles_op);
> +}

regards,
-- 
js
suse labs
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