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net: irda: Fix use-after-free in irtty_open() 

The N_IRDA line discipline may access the previous line discipline's closed
and already-fre private data on open [1].

The tty->disc_data field _never_ refers to valid data on entry to the
line discipline's open() method. Rather, the ldisc is expected to
initialize that field for its own use for the lifetime of the instance
(ie. from open() to close() only).

[1]
    ==================================================================
    BUG: KASAN: use-after-free in irtty_open+0x422/0x550 at addr ffff8800331dd068
    Read of size 4 by task a.out/13960
    =============================================================================
    BUG kmalloc-512 (Tainted: G    B          ): kasan: bad access detected
    -----------------------------------------------------------------------------
    ...
    Call Trace:
     [<ffffffff815fa2ae>] __asan_report_load4_noabort+0x3e/0x40 mm/kasan/report.c:279
     [<ffffffff836938a2>] irtty_open+0x422/0x550 drivers/net/irda/irtty-sir.c:436
     [<ffffffff829f1b80>] tty_ldisc_open.isra.2+0x60/0xa0 drivers/tty/tty_ldisc.c:447
     [<ffffffff829f21c0>] tty_set_ldisc+0x1a0/0x940 drivers/tty/tty_ldisc.c:567
     [<     inline     >] tiocsetd drivers/tty/tty_io.c:2650
     [<ffffffff829da49e>] tty_ioctl+0xace/0x1fd0 drivers/tty/tty_io.c:2883
     [<     inline     >] vfs_ioctl fs/ioctl.c:43
     [<ffffffff816708ac>] do_vfs_ioctl+0x57c/0xe60 fs/ioctl.c:607
     [<     inline     >] SYSC_ioctl fs/ioctl.c:622
     [<ffffffff81671204>] SyS_ioctl+0x74/0x80 fs/ioctl.c:613
     [<ffffffff852a7876>] entry_SYSCALL_64_fastpath+0x16/0x7a

Reported-and-tested-by: Dmitry Vyukov <dvyukov@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Peter Hurley 2016-01-09 17:48:45 -08:00 committed by Greg Kroah-Hartman
parent e9b736d88a
commit 401879c57f
1 changed files with 0 additions and 10 deletions
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10
drivers/net/irda/irtty-sir.c
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@ -430,16 +430,6 @@ static int irtty_open(struct tty_struct *tty)
/* Module stuff handled via irda_ldisc.owner - Jean II */
/* First make sure we're not already connected. */
if (tty->disc_data != NULL) {
priv = tty->disc_data;
if (priv && priv->magic == IRTTY_MAGIC) {
ret = -EEXIST;
goto out;
}
tty->disc_data = NULL; /* ### */
}
/* stop the underlying driver */
irtty_stop_receiver(tty, TRUE);
if (tty->ops->stop)