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