This is a note to let you know that I've just added the patch titled pty: fix possible use after free of tty->driver_data to the 3.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: pty-fix-possible-use-after-free-of-tty-driver_data.patch and it can be found in the queue-3.14 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 2831c89f42dcde440cfdccb9fee9f42d54bbc1ef Mon Sep 17 00:00:00 2001 From: "Herton R. Krzesinski" <herton@xxxxxxxxxx> Date: Mon, 11 Jan 2016 12:07:43 -0200 Subject: pty: fix possible use after free of tty->driver_data From: Herton R. Krzesinski <herton@xxxxxxxxxx> commit 2831c89f42dcde440cfdccb9fee9f42d54bbc1ef upstream. This change fixes a bug for a corner case where we have the the last release from a pty master/slave coming from a previously opened /dev/tty file. When this happens, the tty->driver_data can be stale, due to all ptmx or pts/N files having already been closed before (and thus the inode related to these files, which tty->driver_data points to, being already freed/destroyed). The fix here is to keep a reference on the opened master ptmx inode. We maintain the inode referenced until the final pty_unix98_shutdown, and only pass this inode to devpts_kill_index. Signed-off-by: Herton R. Krzesinski <herton@xxxxxxxxxx> Reviewed-by: Peter Hurley <peter@xxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/tty/pty.c | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-) --- a/drivers/tty/pty.c +++ b/drivers/tty/pty.c @@ -617,7 +617,14 @@ static void pty_unix98_remove(struct tty /* this is called once with whichever end is closed last */ static void pty_unix98_shutdown(struct tty_struct *tty) { - devpts_kill_index(tty->driver_data, tty->index); + struct inode *ptmx_inode; + + if (tty->driver->subtype == PTY_TYPE_MASTER) + ptmx_inode = tty->driver_data; + else + ptmx_inode = tty->link->driver_data; + devpts_kill_index(ptmx_inode, tty->index); + iput(ptmx_inode); /* drop reference we acquired at ptmx_open */ } static const struct tty_operations ptm_unix98_ops = { @@ -708,6 +715,15 @@ static int ptmx_open(struct inode *inode set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */ tty->driver_data = inode; + /* + * In the case where all references to ptmx inode are dropped and we + * still have /dev/tty opened pointing to the master/slave pair (ptmx + * is closed/released before /dev/tty), we must make sure that the inode + * is still valid when we call the final pty_unix98_shutdown, thus we + * hold an additional reference to the ptmx inode + */ + ihold(inode); + tty_add_file(tty, filp); slave_inode = devpts_pty_new(inode, Patches currently in stable-queue which might be from herton@xxxxxxxxxx are queue-3.14/pty-make-sure-super_block-is-still-valid-in-final-dev-tty-close.patch queue-3.14/pty-fix-possible-use-after-free-of-tty-driver_data.patch -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html