From 1c7f227a50d9944c0b6d360c9b9fa0f31004420a Mon Sep 17 00:00:00 2001 From: Peter Hurley Date: Sat, 9 Jan 2016 17:48:45 -0800 Subject: [PATCH] net: irda: Fix use-after-free in irtty_open() commit 401879c57f01cbf2da204ad2e8db910525c6dbea upstream. 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: [] __asan_report_load4_noabort+0x3e/0x40 mm/kasan/report.c:279 [] irtty_open+0x422/0x550 drivers/net/irda/irtty-sir.c:436 [] tty_ldisc_open.isra.2+0x60/0xa0 drivers/tty/tty_ldisc.c:447 [] tty_set_ldisc+0x1a0/0x940 drivers/tty/tty_ldisc.c:567 [< inline >] tiocsetd drivers/tty/tty_io.c:2650 [] tty_ioctl+0xace/0x1fd0 drivers/tty/tty_io.c:2883 [< inline >] vfs_ioctl fs/ioctl.c:43 [] do_vfs_ioctl+0x57c/0xe60 fs/ioctl.c:607 [< inline >] SYSC_ioctl fs/ioctl.c:622 [] SyS_ioctl+0x74/0x80 fs/ioctl.c:613 [] entry_SYSCALL_64_fastpath+0x16/0x7a Reported-and-tested-by: Dmitry Vyukov Cc: Signed-off-by: Peter Hurley Signed-off-by: Greg Kroah-Hartman Signed-off-by: Willy Tarreau --- drivers/net/irda/irtty-sir.c | 10 ---------- 1 file changed, 10 deletions(-) diff --git a/drivers/net/irda/irtty-sir.c b/drivers/net/irda/irtty-sir.c index a41267197839..0d71fa9f0c68 100644 --- a/drivers/net/irda/irtty-sir.c +++ b/drivers/net/irda/irtty-sir.c @@ -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)