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    SubjectRe: [PATCH 28/49] tty: Add a new file /proc/tty/consoles
    On Sat, Oct 23, 2010 at 12:51:29PM +0100, 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.

    PS: "you" above applies to whoever had produced that patch, of course, not
    to Jiri.

    PPS: "device name of stdin of last process opening that file, if that
    stdin happened to be a tty" is an interesting thing to put into global
    variable. What does one do to it?


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