From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752223AbcF0V2D (ORCPT ); Mon, 27 Jun 2016 17:28:03 -0400 Received: from mail-pf0-f196.google.com ([209.85.192.196]:35144 "EHLO mail-pf0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751879AbcF0V2B (ORCPT ); Mon, 27 Jun 2016 17:28:01 -0400 Date: Mon, 27 Jun 2016 14:27:56 -0700 From: Dmitry Torokhov To: Sasha Levin Cc: gregkh@linuxfoundation.org, jslaby@suse.com, pavel@ucw.cz, LKML Subject: Re: tty/vt/keyboard: out of bounds access in do_compute_shiftstate Message-ID: <20160627212756.GB22620@dtor-ws> References: <574B2C6C.7060402@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <574B2C6C.7060402@oracle.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, May 29, 2016 at 01:52:44PM -0400, Sasha Levin wrote: > Hi all, > > I've hit the following while fuzzing with syzkaller inside a KVM tools guest > running the latest -next kernel: > > [ 2662.777566] BUG: KASAN: global-out-of-bounds in do_compute_shiftstate+0x161/0x370 at addr ffffffffb2e686a0 > > [ 2662.777592] Read of size 2 by task syz-executor/30576 > > [ 2662.777676] Address belongs to variable plain_map+0x200/0x3540 > > [ 2662.777727] CPU: 2 PID: 30576 Comm: syz-executor Tainted: G B 4.6.0-next-20160527-sasha-00024-g6ab0dc9-dirty #3098 > > [ 2662.777792] 1ffff1001635bde7 00000000dc4d92d7 ffff8800b1adefc0 ffffffffa3fd0b37 > > [ 2662.777826] ffffffff00000002 fffffbfff5deeda4 0000000041b58ab3 ffffffffae8dd830 > > [ 2662.777862] ffffffffa3fd09c8 ffffffffa23fa2e8 ffff8800b1adef98 ffff8801d42a20f8 > > [ 2662.777868] Call Trace: > > [ 2662.777935] dump_stack (lib/dump_stack.c:53) > [ 2662.778136] kasan_report_error (include/linux/kasan.h:28 mm/kasan/report.c:211 mm/kasan/report.c:277) > [ 2662.778265] __asan_report_load2_noabort (mm/kasan/report.c:317) > [ 2662.778318] do_compute_shiftstate (drivers/tty/vt/keyboard.c:386) > [ 2662.778332] fn_null (drivers/tty/vt/keyboard.c:625) > [ 2662.778345] k_spec (drivers/tty/vt/keyboard.c:645) > [ 2662.778361] kbd_event (drivers/tty/vt/keyboard.c:1459 drivers/tty/vt/keyboard.c:1475) > [ 2662.778907] input_to_handler (drivers/input/input.c:120 (discriminator 3)) > [ 2662.778926] input_pass_values (drivers/input/input.c:148) > [ 2662.778944] input_handle_event (drivers/input/input.c:406) > [ 2662.779015] input_inject_event (include/linux/rcupdate.h:910 drivers/input/input.c:467) > [ 2662.779034] evdev_do_ioctl (drivers/input/evdev.c:1102) > [ 2662.779271] evdev_ioctl_handler (drivers/input/evdev.c:1302) > [ 2662.779305] evdev_ioctl (drivers/input/evdev.c:1312) > [ 2662.779320] do_vfs_ioctl (fs/ioctl.c:44 fs/ioctl.c:674) > [ 2662.779463] SyS_ioctl (fs/ioctl.c:689 fs/ioctl.c:680) > [ 2662.779511] do_syscall_64 (arch/x86/entry/common.c:350) > [ 2662.779530] entry_SYSCALL64_slow_path (arch/x86/entry/entry_64.S:251) > [ 2662.779535] Memory state around the buggy address: > > [ 2662.779566] ffffffffb2e68580: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > > [ 2662.779579] ffffffffb2e68600: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > > [ 2662.779589] >ffffffffb2e68680: 00 00 00 00 fa fa fa fa 00 00 00 00 00 00 00 00 > > [ 2662.779594] ^ > > [ 2662.779604] ffffffffb2e68700: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > > [ 2662.779615] ffffffffb2e68780: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 I think this happens because keymap size in keyboard.c is smaller than keymaps in input devices. Does the patch below fixes this? Thanks. -- Dmitry tty/vt/keyboard: fix OOB access in do_compute_shiftstate() From: Dmitry Torokhov The size of individual keymap in drivers/tty/vt/keyboard.c is NR_KEYS, which is currently 256, whereas number of keys/buttons in input device (and therefor in key_down) is much larger - KEY_CNT - 768, and that can cause out-of-bound access when we do sym = U(key_maps[0][k]); with large 'k'. To fix it we should not attempt iterating beyond smaller of NR_KEYS and KEY_CNT. Also while at it let's switch to for_each_set_bit() instead of open-coding it. Reported-by: Sasha Levin Cc: stable@vger.kernel.org Signed-off-by: Dmitry Torokhov --- drivers/tty/vt/keyboard.c | 30 +++++++++--------------------- 1 file changed, 9 insertions(+), 21 deletions(-) diff --git a/drivers/tty/vt/keyboard.c b/drivers/tty/vt/keyboard.c index f973bfc..1e93a37 100644 --- a/drivers/tty/vt/keyboard.c +++ b/drivers/tty/vt/keyboard.c @@ -366,34 +366,22 @@ static void to_utf8(struct vc_data *vc, uint c) static void do_compute_shiftstate(void) { - unsigned int i, j, k, sym, val; + unsigned int k, sym, val; shift_state = 0; memset(shift_down, 0, sizeof(shift_down)); - for (i = 0; i < ARRAY_SIZE(key_down); i++) { - - if (!key_down[i]) + for_each_set_bit(k, key_down, min(NR_KEYS, KEY_CNT)) { + sym = U(key_maps[0][k]); + if (KTYP(sym) != KT_SHIFT && KTYP(sym) != KT_SLOCK) continue; - k = i * BITS_PER_LONG; - - for (j = 0; j < BITS_PER_LONG; j++, k++) { - - if (!test_bit(k, key_down)) - continue; + val = KVAL(sym); + if (val == KVAL(K_CAPSSHIFT)) + val = KVAL(K_SHIFT); - sym = U(key_maps[0][k]); - if (KTYP(sym) != KT_SHIFT && KTYP(sym) != KT_SLOCK) - continue; - - val = KVAL(sym); - if (val == KVAL(K_CAPSSHIFT)) - val = KVAL(K_SHIFT); - - shift_down[val]++; - shift_state |= (1 << val); - } + shift_down[val]++; + shift_state |= BIT(val); } }