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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>
This commit is contained in:
Jiri Slaby 2011-11-11 10:47:23 +01:00 committed by Greg Kroah-Hartman
parent 2cd0050cf3
commit 955787ca94
1 changed files with 57 additions and 44 deletions
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101
drivers/tty/tty_io.c
View File

@ -1556,6 +1556,62 @@ static void release_tty(struct tty_struct *tty, int idx)
tty_kref_put(tty);
}
/**
* tty_release_checks - check a tty before real release
* @tty: tty to check
* @o_tty: link of @tty (if any)
* @idx: index of the tty
*
* Performs some paranoid checking before true release of the @tty.
* This is a no-op unless TTY_PARANOIA_CHECK is defined.
*/
static int tty_release_checks(struct tty_struct *tty, struct tty_struct *o_tty,
int idx)
{
#ifdef TTY_PARANOIA_CHECK
if (idx < 0 || idx >= tty->driver->num) {
printk(KERN_DEBUG "tty_release_dev: bad idx when trying to "
"free (%s)\n", tty->name);
return -1;
}
/* not much to check for devpts */
if (tty->driver->flags & TTY_DRIVER_DEVPTS_MEM)
return 0;
if (tty != tty->driver->ttys[idx]) {
printk(KERN_DEBUG "tty_release_dev: driver.table[%d] not tty "
"for (%s)\n", idx, tty->name);
return -1;
}
if (tty->termios != tty->driver->termios[idx]) {
printk(KERN_DEBUG "tty_release_dev: driver.termios[%d] not termios "
"for (%s)\n",
idx, tty->name);
return -1;
}
if (tty->driver->other) {
if (o_tty != tty->driver->other->ttys[idx]) {
printk(KERN_DEBUG "tty_release_dev: other->table[%d] "
"not o_tty for (%s)\n",
idx, tty->name);
return -1;
}
if (o_tty->termios != tty->driver->other->termios[idx]) {
printk(KERN_DEBUG "tty_release_dev: other->termios[%d] "
"not o_termios for (%s)\n",
idx, tty->name);
return -1;
}
if (o_tty->link != tty) {
printk(KERN_DEBUG "tty_release_dev: bad pty pointers\n");
return -1;
}
}
#endif
return 0;
}
/**
* tty_release - vfs callback for close
* @inode: inode of tty
@ -1598,59 +1654,16 @@ int tty_release(struct inode *inode, struct file *filp)
devpts = (tty->driver->flags & TTY_DRIVER_DEVPTS_MEM) != 0;
o_tty = tty->link;
#ifdef TTY_PARANOIA_CHECK
if (idx < 0 || idx >= tty->driver->num) {
printk(KERN_DEBUG "tty_release_dev: bad idx when trying to "
"free (%s)\n", tty->name);
if (tty_release_checks(tty, o_tty, idx)) {
tty_unlock();
return 0;
}
if (!devpts) {
if (tty != tty->driver->ttys[idx]) {
tty_unlock();
printk(KERN_DEBUG "tty_release_dev: driver.table[%d] not tty "
"for (%s)\n", idx, tty->name);
return 0;
}
if (tty->termios != tty->driver->termios[idx]) {
tty_unlock();
printk(KERN_DEBUG "tty_release_dev: driver.termios[%d] not termios "
"for (%s)\n",
idx, tty->name);
return 0;
}
}
#endif
#ifdef TTY_DEBUG_HANGUP
printk(KERN_DEBUG "tty_release_dev of %s (tty count=%d)...",
tty_name(tty, buf), tty->count);
#endif
#ifdef TTY_PARANOIA_CHECK
if (tty->driver->other &&
!(tty->driver->flags & TTY_DRIVER_DEVPTS_MEM)) {
if (o_tty != tty->driver->other->ttys[idx]) {
tty_unlock();
printk(KERN_DEBUG "tty_release_dev: other->table[%d] "
"not o_tty for (%s)\n",
idx, tty->name);
return 0 ;
}
if (o_tty->termios != tty->driver->other->termios[idx]) {
tty_unlock();
printk(KERN_DEBUG "tty_release_dev: other->termios[%d] "
"not o_termios for (%s)\n",
idx, tty->name);
return 0;
}
if (o_tty->link != tty) {
tty_unlock();
printk(KERN_DEBUG "tty_release_dev: bad pty pointers\n");
return 0;
}
}
#endif
if (tty->ops->close)
tty->ops->close(tty, filp);