From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932831AbbLXPnX (ORCPT ); Thu, 24 Dec 2015 10:43:23 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:51459 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753812AbbLXPmd (ORCPT ); Thu, 24 Dec 2015 10:42:33 -0500 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Peter Hurley" , "David S. Miller" Date: Thu, 24 Dec 2015 15:37:42 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.2 40/77] wan/x25: Fix use-after-free in x25_asy_open_tty() In-Reply-To: X-SA-Exim-Connect-IP: 192.168.4.247 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2.75-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Peter Hurley commit ee9159ddce14bc1dec9435ae4e3bd3153e783706 upstream. The N_X25 line discipline may access the previous line discipline's closed and already-freed 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] [ 634.336761] ================================================================== [ 634.338226] BUG: KASAN: use-after-free in x25_asy_open_tty+0x13d/0x490 at addr ffff8800a743efd0 [ 634.339558] Read of size 4 by task syzkaller_execu/8981 [ 634.340359] ============================================================================= [ 634.341598] BUG kmalloc-512 (Not tainted): kasan: bad access detected ... [ 634.405018] Call Trace: [ 634.405277] dump_stack (lib/dump_stack.c:52) [ 634.405775] print_trailer (mm/slub.c:655) [ 634.406361] object_err (mm/slub.c:662) [ 634.406824] kasan_report_error (mm/kasan/report.c:138 mm/kasan/report.c:236) [ 634.409581] __asan_report_load4_noabort (mm/kasan/report.c:279) [ 634.411355] x25_asy_open_tty (drivers/net/wan/x25_asy.c:559 (discriminator 1)) [ 634.413997] tty_ldisc_open.isra.2 (drivers/tty/tty_ldisc.c:447) [ 634.414549] tty_set_ldisc (drivers/tty/tty_ldisc.c:567) [ 634.415057] tty_ioctl (drivers/tty/tty_io.c:2646 drivers/tty/tty_io.c:2879) [ 634.423524] do_vfs_ioctl (fs/ioctl.c:43 fs/ioctl.c:607) [ 634.427491] SyS_ioctl (fs/ioctl.c:622 fs/ioctl.c:613) [ 634.427945] entry_SYSCALL_64_fastpath (arch/x86/entry/entry_64.S:188) Reported-and-tested-by: Sasha Levin Signed-off-by: Peter Hurley Signed-off-by: David S. Miller Signed-off-by: Ben Hutchings --- drivers/net/wan/x25_asy.c | 6 +----- 1 file changed, 1 insertion(+), 5 deletions(-) --- a/drivers/net/wan/x25_asy.c +++ b/drivers/net/wan/x25_asy.c @@ -547,16 +547,12 @@ static void x25_asy_receive_buf(struct t static int x25_asy_open_tty(struct tty_struct *tty) { - struct x25_asy *sl = tty->disc_data; + struct x25_asy *sl; int err; if (tty->ops->write == NULL) return -EOPNOTSUPP; - /* First make sure we're not already connected. */ - if (sl && sl->magic == X25_ASY_MAGIC) - return -EEXIST; - /* OK. Find a free X.25 channel to use. */ sl = x25_asy_alloc(); if (sl == NULL)