lkml.org 
[lkml]   [2011]   [Nov]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH v2 6/7] TTY: move debug checking out of tty_release
Date
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>
Cc: Greg Kroah-Hartman <gregkh@suse.de>
---
drivers/tty/tty_io.c | 101 ++++++++++++++++++++++++++++----------------------
1 files changed, 57 insertions(+), 44 deletions(-)

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 76e66ff..b874b6d 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -1557,6 +1557,62 @@ static void release_tty(struct tty_struct *tty, int idx)
}

/**
+ * 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
* @filp: file pointer for handle to 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);

--
1.7.7



\
 
 \ /
  Last update: 2011-11-11 10:49    [W:0.072 / U:1.068 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site