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    SubjectRe: [PATCH v2] media:dvb-frontends:Remove dvb_pll_devcount and id module parameters.
    Sean,

    Please pardon the late reply. See my responses inline below:

    On Wed, Jul 24, 2019 at 1:36 AM Sean Young <sean@mess.org> wrote:
    >
    > On Sat, Jul 20, 2019 at 11:43:02AM +0530, Vandana BN wrote:
    > > 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 would be to check if DVB_PLL_MAX devices are attached and if so return
    > > NULL from dvb_pll_attach(). But this will put a limit on the number of
    > > devices that can be attached.
    > > Also dvb_pll_devcount and "id" module parameter are used for debugging
    > > purpose to override/force PLL type.
    > > So this patch removes these module parameters.
    > >
    > > Reported-by: syz...@syzkaller.appspotmail.com
    > >
    > > 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@gmail.com>
    > > ---
    > > drivers/media/dvb-frontends/dvb-pll.c | 19 +++----------------
    > > 1 file changed, 3 insertions(+), 16 deletions(-)
    > >
    > > diff --git a/drivers/media/dvb-frontends/dvb-pll.c b/drivers/media/dvb-frontends/dvb-pll.c
    > > index ba0c49107bd2..c3a04751e9cf 100644
    > > --- a/drivers/media/dvb-frontends/dvb-pll.c
    > > +++ b/drivers/media/dvb-frontends/dvb-pll.c
    > > @@ -33,19 +33,11 @@ struct dvb_pll_priv {
    > > u32 bandwidth;
    > > };
    > >
    > > -#define DVB_PLL_MAX 64
    > > -
    > > -static unsigned int dvb_pll_devcount;
    > >
    > > static int debug;
    > > module_param(debug, int, 0644);
    > > MODULE_PARM_DESC(debug, "enable verbose debug messages");
    > >
    > > -static unsigned int id[DVB_PLL_MAX] =
    > > - { [ 0 ... (DVB_PLL_MAX-1) ] = DVB_PLL_UNDEFINED };
    > > -module_param_array(id, int, NULL, 0644);
    > > -MODULE_PARM_DESC(id, "force pll id to use (DEBUG ONLY)");
    > > -
    >
    > Mike, you introduced this module parameter in:
    >
    > commit 05a4611b5d71ad6f968fdeef092c24914570898b
    > Author: Michael Krufky <mkrufky@linuxtv.org>
    > AuthorDate: Fri Sep 7 18:19:57 2007 -0300
    >
    > V4L/DVB (6228): dvb-pll: add module option to specify rf input
    >
    > Add a module option to dvb-pll, called "input" to specify which rf
    > input to use on devices with multiple rf inputs. If the module option
    > is not specified, then the driver will autoselect the rf input, as per
    > previous behavior.
    >
    > Signed-off-by: Michael Krufky <mkrufky@linuxtv.org>
    > Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>
    >
    > What was your motivation?

    Sean,

    This was to support DVB-T/C & ATSC/QAM-B cards that had multiple RF
    input options intended to be used to connect an aerial and a Cable TV
    input source simultaneously. It should not be removed.

    -Mike

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