KMSAN: uninit-value in smsc75xx_bind

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    beaab8a3 fix KASAN build
git tree:       kmsan
console output: https://syzkaller.appspot.com/x/log.txt?x=13d7b65c600000
kernel config:  https://syzkaller.appspot.com/x/.config?x=4db781fe35a84ef5
dashboard link: https://syzkaller.appspot.com/bug?extid=6966546b78d050bb0b5d
compiler:       clang version 9.0.0 (/home/glider/llvm/clang  
80fee25776c2fb61e74c1ecb1a523375c2500b69)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=14ab9ef0600000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=11be2b34600000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+6966546b78d050bb0b5d@xxxxxxxxxxxxxxxxxxxxxxxxx

==================================================================
BUG: KMSAN: uninit-value in smsc75xx_wait_ready  
drivers/net/usb/smsc75xx.c:976 [inline]
BUG: KMSAN: uninit-value in smsc75xx_bind+0x541/0x12d0  
drivers/net/usb/smsc75xx.c:1483
CPU: 0 PID: 2892 Comm: kworker/0:2 Not tainted 5.2.0+ #15
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+0x191/0x1f0 lib/dump_stack.c:113
 kmsan_report+0x162/0x2d0 mm/kmsan/kmsan_report.c:109
 __msan_warning+0x75/0xe0 mm/kmsan/kmsan_instr.c:294
 smsc75xx_wait_ready drivers/net/usb/smsc75xx.c:976 [inline]
 smsc75xx_bind+0x541/0x12d0 drivers/net/usb/smsc75xx.c:1483
 usbnet_probe+0x10d3/0x3950 drivers/net/usb/usbnet.c:1722
 usb_probe_interface+0xd19/0x1310 drivers/usb/core/driver.c:361
 really_probe+0x1344/0x1d90 drivers/base/dd.c:513
 driver_probe_device+0x1ba/0x510 drivers/base/dd.c:670
 __device_attach_driver+0x5b8/0x790 drivers/base/dd.c:777
 bus_for_each_drv+0x28e/0x3b0 drivers/base/bus.c:454
 __device_attach+0x489/0x750 drivers/base/dd.c:843
 device_initial_probe+0x4a/0x60 drivers/base/dd.c:890
 bus_probe_device+0x131/0x390 drivers/base/bus.c:514
 device_add+0x25b5/0x2df0 drivers/base/core.c:2111
 usb_set_configuration+0x309f/0x3710 drivers/usb/core/message.c:2027
 generic_probe+0xe7/0x280 drivers/usb/core/generic.c:210
 usb_probe_device+0x146/0x200 drivers/usb/core/driver.c:266
 really_probe+0x1344/0x1d90 drivers/base/dd.c:513
 driver_probe_device+0x1ba/0x510 drivers/base/dd.c:670
 __device_attach_driver+0x5b8/0x790 drivers/base/dd.c:777
 bus_for_each_drv+0x28e/0x3b0 drivers/base/bus.c:454
 __device_attach+0x489/0x750 drivers/base/dd.c:843
 device_initial_probe+0x4a/0x60 drivers/base/dd.c:890
 bus_probe_device+0x131/0x390 drivers/base/bus.c:514
 device_add+0x25b5/0x2df0 drivers/base/core.c:2111
 usb_new_device+0x23e5/0x2fb0 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+0x5853/0x7320 drivers/usb/core/hub.c:5432
 process_one_work+0x1572/0x1f00 kernel/workqueue.c:2269
 process_scheduled_works kernel/workqueue.c:2331 [inline]
 worker_thread+0x189c/0x2460 kernel/workqueue.c:2417
 kthread+0x4b5/0x4f0 kernel/kthread.c:256
 ret_from_fork+0x35/0x40 arch/x86/entry/entry_64.S:355

Local variable description: ----buf.i93@smsc75xx_bind
Variable was created at:
 __smsc75xx_read_reg drivers/net/usb/smsc75xx.c:83 [inline]
 smsc75xx_wait_ready drivers/net/usb/smsc75xx.c:969 [inline]
 smsc75xx_bind+0x44c/0x12d0 drivers/net/usb/smsc75xx.c:1483
 usbnet_probe+0x10d3/0x3950 drivers/net/usb/usbnet.c:1722
==================================================================


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