[PATCH] media:dvb-frontends:Return if Max devices are added in dvb_pll_attach().

[Vandana BN]

Syzbot reported global-out-of-bounds Read in dvb_pll_attach, while
accessing id[dvb_pll_devcount], because dvb_pll_devcount was 65,
that is more than size of 'id' which is DVB_PLL_MAX(64).

Fix is to check if DVB_PLL_MAX devices are attached and if so return
NULL from dvb_pll_attach().

Reported-by: syz...@xxxxxxxxxxxxxxxxxxxxxxxxx

usb 1-1: dvb_usb_v2: will pass the complete MPEG2 transport stream to the
software demuxer
dvbdev: DVB: registering new adapter (774 Friio White ISDB-T USB2.0)
usb 1-1: media controller created
dvbdev: dvb_create_media_entity: media entity 'dvb-demux' registered.
tc90522 0-0018: Toshiba TC90522 attached.
usb 1-1: DVB: registering adapter 0 frontend 0 (Toshiba TC90522 ISDB-T
module)...
dvbdev: dvb_create_media_entity: media entity 'Toshiba TC90522 ISDB-T
module' registered.
==================================================================
BUG: KASAN: global-out-of-bounds in dvb_pll_attach+0x6c5/0x830
drivers/media/dvb-frontends/dvb-pll.c:798
Read of size 4 at addr ffffffff89c9e5e0 by task kworker/0:1/12

CPU: 0 PID: 12 Comm: kworker/0:1 Not tainted 5.2.0-rc6+ #13
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Workqueue: usb_hub_wq hub_event
Call Trace:
  __dump_stack lib/dump_stack.c:77 [inline]
  dump_stack+0xca/0x13e lib/dump_stack.c:113
  print_address_description+0x67/0x231 mm/kasan/report.c:188
  __kasan_report.cold+0x1a/0x32 mm/kasan/report.c:317
  kasan_report+0xe/0x20 mm/kasan/common.c:614
  dvb_pll_attach+0x6c5/0x830 drivers/media/dvb-frontends/dvb-pll.c:798
  dvb_pll_probe+0xfe/0x174 drivers/media/dvb-frontends/dvb-pll.c:877
  i2c_device_probe+0x790/0xaa0 drivers/i2c/i2c-core-base.c:389
  really_probe+0x281/0x660 drivers/base/dd.c:509
  driver_probe_device+0x104/0x210 drivers/base/dd.c:670
  __device_attach_driver+0x1c2/0x220 drivers/base/dd.c:777
  bus_for_each_drv+0x15c/0x1e0 drivers/base/bus.c:454
  __device_attach+0x217/0x360 drivers/base/dd.c:843
  bus_probe_device+0x1e4/0x290 drivers/base/bus.c:514
  device_add+0xae6/0x16f0 drivers/base/core.c:2111
  i2c_new_client_device+0x5b3/0xc40 drivers/i2c/i2c-core-base.c:778
  i2c_new_device+0x19/0x50 drivers/i2c/i2c-core-base.c:821
  dvb_module_probe+0xf9/0x220 drivers/media/dvb-core/dvbdev.c:985
  friio_tuner_attach+0x125/0x1d0 drivers/media/usb/dvb-usb-v2/gl861.c:536
  dvb_usbv2_adapter_frontend_init
drivers/media/usb/dvb-usb-v2/dvb_usb_core.c:675 [inline]
  dvb_usbv2_adapter_init drivers/media/usb/dvb-usb-v2/dvb_usb_core.c:804
[inline]
  dvb_usbv2_init drivers/media/usb/dvb-usb-v2/dvb_usb_core.c:865 [inline]
  dvb_usbv2_probe.cold+0x24dc/0x255d
drivers/media/usb/dvb-usb-v2/dvb_usb_core.c:980
  usb_probe_interface+0x305/0x7a0 drivers/usb/core/driver.c:361
  really_probe+0x281/0x660 drivers/base/dd.c:509
  driver_probe_device+0x104/0x210 drivers/base/dd.c:670
  __device_attach_driver+0x1c2/0x220 drivers/base/dd.c:777
  bus_for_each_drv+0x15c/0x1e0 drivers/base/bus.c:454
  __device_attach+0x217/0x360 drivers/base/dd.c:843
  bus_probe_device+0x1e4/0x290 drivers/base/bus.c:514
  device_add+0xae6/0x16f0 drivers/base/core.c:2111
  usb_set_configuration+0xdf6/0x1670 drivers/usb/core/message.c:2023
  generic_probe+0x9d/0xd5 drivers/usb/core/generic.c:210
  usb_probe_device+0x99/0x100 drivers/usb/core/driver.c:266
  really_probe+0x281/0x660 drivers/base/dd.c:509
  driver_probe_device+0x104/0x210 drivers/base/dd.c:670
  __device_attach_driver+0x1c2/0x220 drivers/base/dd.c:777
  bus_for_each_drv+0x15c/0x1e0 drivers/base/bus.c:454
  __device_attach+0x217/0x360 drivers/base/dd.c:843
  bus_probe_device+0x1e4/0x290 drivers/base/bus.c:514
  device_add+0xae6/0x16f0 drivers/base/core.c:2111
  usb_new_device.cold+0x8c1/0x1016 drivers/usb/core/hub.c:2534
  hub_port_connect drivers/usb/core/hub.c:5089 [inline]
  hub_port_connect_change drivers/usb/core/hub.c:5204 [inline]
  port_event drivers/usb/core/hub.c:5350 [inline]
  hub_event+0x1ada/0x3590 drivers/usb/core/hub.c:5432
  process_one_work+0x905/0x1570 kernel/workqueue.c:2269
  process_scheduled_works kernel/workqueue.c:2331 [inline]
  worker_thread+0x7ab/0xe20 kernel/workqueue.c:2417
  kthread+0x30b/0x410 kernel/kthread.c:255
  ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352

The buggy address belongs to the variable:
  id+0x100/0x120

Memory state around the buggy address:
  ffffffff89c9e480: fa fa fa fa 00 00 fa fa fa fa fa fa 00 00 00 00
  ffffffff89c9e500: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> ffffffff89c9e580: 00 00 00 00 00 00 00 00 00 00 00 00 fa fa fa fa
                                                        ^
  ffffffff89c9e600: 04 fa fa fa fa fa fa fa 04 fa fa fa fa fa fa fa
  ffffffff89c9e680: 04 fa fa fa fa fa fa fa 04 fa fa fa fa fa fa fa
==================================================================

Signed-off-by: Vandana BN <bnvandana@xxxxxxxxx>
---
 drivers/media/dvb-frontends/dvb-pll.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/media/dvb-frontends/dvb-pll.c b/drivers/media/dvb-frontends/dvb-pll.c
index ba0c49107bd2..c850f1d69bce 100644
--- a/drivers/media/dvb-frontends/dvb-pll.c
+++ b/drivers/media/dvb-frontends/dvb-pll.c
@@ -788,6 +788,9 @@ struct dvb_frontend *dvb_pll_attach(struct dvb_frontend *fe, int pll_addr,
 	int ret;
 	const struct dvb_pll_desc *desc;

+	if (dvb_pll_devcount > DVB_PLL_MAX - 1)
+		return NULL;
+
 	b1 = kmalloc(1, GFP_KERNEL);
 	if (!b1)
 		return NULL;
-- 
2.17.1