Re: KMSAN: uninit-value in tda8083_attach

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit:    ce8056d1 wip: changed copy_from_user where instrumented
git tree:       https://github.com/google/kmsan.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=164cd76a900000
kernel config:  https://syzkaller.appspot.com/x/.config?x=3afe005fb99591f
dashboard link: https://syzkaller.appspot.com/bug?extid=909a91e75919efd2b557
compiler:       clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=160a9c7a900000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=165d7f6a900000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+909a91e75919efd2b557@xxxxxxxxxxxxxxxxxxxxxxxxx

usb 1-1: config 0 descriptor??
usb 1-1: selecting invalid altsetting 1
ttusb_init_controller: error
dvbdev: DVB: registering new adapter (Technotrend/Hauppauge Nova-USB)
=====================================================
BUG: KMSAN: uninit-value in tda8083_attach+0x55a/0x6d0 drivers/media/dvb-frontends/tda8083.c:428
CPU: 1 PID: 49 Comm: kworker/1:1 Not tainted 5.8.0-rc5-syzkaller #0
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+0x21c/0x280 lib/dump_stack.c:118
 kmsan_report+0xf7/0x1e0 mm/kmsan/kmsan_report.c:121
 __msan_warning+0x58/0xa0 mm/kmsan/kmsan_instr.c:215
 tda8083_attach+0x55a/0x6d0 drivers/media/dvb-frontends/tda8083.c:428
 frontend_init drivers/media/usb/ttusb-budget/dvb-ttusb-budget.c:1574 [inline]
 ttusb_probe+0x4238/0x5040 drivers/media/usb/ttusb-budget/dvb-ttusb-budget.c:1739
 usb_probe_interface+0xece/0x1550 drivers/usb/core/driver.c:374
 really_probe+0xf20/0x20b0 drivers/base/dd.c:529
 driver_probe_device+0x293/0x390 drivers/base/dd.c:701
 __device_attach_driver+0x63f/0x830 drivers/base/dd.c:807
 bus_for_each_drv+0x2ca/0x3f0 drivers/base/bus.c:431
 __device_attach+0x4e2/0x7f0 drivers/base/dd.c:873
 device_initial_probe+0x4a/0x60 drivers/base/dd.c:920
 bus_probe_device+0x177/0x3d0 drivers/base/bus.c:491
 device_add+0x3b0e/0x40d0 drivers/base/core.c:2680
 usb_set_configuration+0x380f/0x3f10 drivers/usb/core/message.c:2032
 usb_generic_driver_probe+0x138/0x300 drivers/usb/core/generic.c:241
 usb_probe_device+0x311/0x490 drivers/usb/core/driver.c:272
 really_probe+0xf20/0x20b0 drivers/base/dd.c:529
 driver_probe_device+0x293/0x390 drivers/base/dd.c:701
 __device_attach_driver+0x63f/0x830 drivers/base/dd.c:807
 bus_for_each_drv+0x2ca/0x3f0 drivers/base/bus.c:431
 __device_attach+0x4e2/0x7f0 drivers/base/dd.c:873
 device_initial_probe+0x4a/0x60 drivers/base/dd.c:920
 bus_probe_device+0x177/0x3d0 drivers/base/bus.c:491
 device_add+0x3b0e/0x40d0 drivers/base/core.c:2680
 usb_new_device+0x1bd4/0x2a30 drivers/usb/core/hub.c:2554
 hub_port_connect drivers/usb/core/hub.c:5208 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5348 [inline]
 port_event drivers/usb/core/hub.c:5494 [inline]
 hub_event+0x5e7b/0x8a70 drivers/usb/core/hub.c:5576
 process_one_work+0x1688/0x2140 kernel/workqueue.c:2269
 worker_thread+0x10bc/0x2730 kernel/workqueue.c:2415
 kthread+0x551/0x590 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293

Local variable ----reg1.addr.i.i@tda8083_attach created at:
 tda8083_readregs drivers/media/dvb-frontends/tda8083.c:425 [inline]
 tda8083_readreg drivers/media/dvb-frontends/tda8083.c:83 [inline]
 tda8083_attach+0x1af/0x6d0 drivers/media/dvb-frontends/tda8083.c:428
 tda8083_readregs drivers/media/dvb-frontends/tda8083.c:425 [inline]
 tda8083_readreg drivers/media/dvb-frontends/tda8083.c:83 [inline]
 tda8083_attach+0x1af/0x6d0 drivers/media/dvb-frontends/tda8083.c:428
=====================================================