TTY: move debug checking out of tty_release
There is no need to taint the tty_release code with paranoia checking. So move it out of line to a separate function. Making thus tty_release more readable. [v2] don't introduce a hard to reproduce use after free (scheduled work would need to preempt the current thread) Signed-off-by: Jiri Slaby <jslaby@suse.cz> Cc: Alan Cox <alan@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
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1 changed files with 57 additions and 44 deletions
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@ -1556,6 +1556,62 @@ static void release_tty(struct tty_struct *tty, int idx)
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tty_kref_put(tty);
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}
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/**
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* tty_release_checks - check a tty before real release
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* @tty: tty to check
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* @o_tty: link of @tty (if any)
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* @idx: index of the tty
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*
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* Performs some paranoid checking before true release of the @tty.
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* This is a no-op unless TTY_PARANOIA_CHECK is defined.
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*/
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static int tty_release_checks(struct tty_struct *tty, struct tty_struct *o_tty,
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int idx)
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{
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#ifdef TTY_PARANOIA_CHECK
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if (idx < 0 || idx >= tty->driver->num) {
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printk(KERN_DEBUG "tty_release_dev: bad idx when trying to "
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"free (%s)\n", tty->name);
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return -1;
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}
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/* not much to check for devpts */
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if (tty->driver->flags & TTY_DRIVER_DEVPTS_MEM)
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return 0;
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if (tty != tty->driver->ttys[idx]) {
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printk(KERN_DEBUG "tty_release_dev: driver.table[%d] not tty "
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"for (%s)\n", idx, tty->name);
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return -1;
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}
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if (tty->termios != tty->driver->termios[idx]) {
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printk(KERN_DEBUG "tty_release_dev: driver.termios[%d] not termios "
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"for (%s)\n",
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idx, tty->name);
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return -1;
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}
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if (tty->driver->other) {
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if (o_tty != tty->driver->other->ttys[idx]) {
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printk(KERN_DEBUG "tty_release_dev: other->table[%d] "
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"not o_tty for (%s)\n",
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idx, tty->name);
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return -1;
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}
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if (o_tty->termios != tty->driver->other->termios[idx]) {
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printk(KERN_DEBUG "tty_release_dev: other->termios[%d] "
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"not o_termios for (%s)\n",
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idx, tty->name);
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return -1;
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}
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if (o_tty->link != tty) {
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printk(KERN_DEBUG "tty_release_dev: bad pty pointers\n");
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return -1;
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}
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}
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#endif
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return 0;
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}
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/**
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* tty_release - vfs callback for close
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* @inode: inode of tty
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@ -1598,59 +1654,16 @@ int tty_release(struct inode *inode, struct file *filp)
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devpts = (tty->driver->flags & TTY_DRIVER_DEVPTS_MEM) != 0;
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o_tty = tty->link;
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#ifdef TTY_PARANOIA_CHECK
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if (idx < 0 || idx >= tty->driver->num) {
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printk(KERN_DEBUG "tty_release_dev: bad idx when trying to "
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"free (%s)\n", tty->name);
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if (tty_release_checks(tty, o_tty, idx)) {
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tty_unlock();
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return 0;
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}
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if (!devpts) {
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if (tty != tty->driver->ttys[idx]) {
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tty_unlock();
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printk(KERN_DEBUG "tty_release_dev: driver.table[%d] not tty "
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"for (%s)\n", idx, tty->name);
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return 0;
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}
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if (tty->termios != tty->driver->termios[idx]) {
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tty_unlock();
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printk(KERN_DEBUG "tty_release_dev: driver.termios[%d] not termios "
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"for (%s)\n",
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idx, tty->name);
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return 0;
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}
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}
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#endif
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#ifdef TTY_DEBUG_HANGUP
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printk(KERN_DEBUG "tty_release_dev of %s (tty count=%d)...",
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tty_name(tty, buf), tty->count);
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#endif
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#ifdef TTY_PARANOIA_CHECK
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if (tty->driver->other &&
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!(tty->driver->flags & TTY_DRIVER_DEVPTS_MEM)) {
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if (o_tty != tty->driver->other->ttys[idx]) {
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tty_unlock();
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printk(KERN_DEBUG "tty_release_dev: other->table[%d] "
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"not o_tty for (%s)\n",
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idx, tty->name);
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return 0 ;
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}
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if (o_tty->termios != tty->driver->other->termios[idx]) {
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tty_unlock();
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printk(KERN_DEBUG "tty_release_dev: other->termios[%d] "
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"not o_termios for (%s)\n",
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idx, tty->name);
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return 0;
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}
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if (o_tty->link != tty) {
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tty_unlock();
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printk(KERN_DEBUG "tty_release_dev: bad pty pointers\n");
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return 0;
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}
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}
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#endif
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if (tty->ops->close)
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tty->ops->close(tty, filp);
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