KMSAN: uninit-value in smsc75xx_wait_eeprom

KMSAN: uninit-value in smsc75xx_wait_eeprom

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    ae0c578a kmsan: include gfp.h from kmsan.h
git tree:       kmsan
console output: https://syzkaller.appspot.com/x/log.txt?x=10e4f474600000
kernel config:  https://syzkaller.appspot.com/x/.config?x=27abc558ecb16a3b
dashboard link: https://syzkaller.appspot.com/bug?extid=532222e4d7ddadadd1c8
compiler:       clang version 9.0.0 (/home/glider/llvm/clang  
80fee25776c2fb61e74c1ecb1a523375c2500b69)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+532222e4d7ddadadd1c8@syzkaller.appspotmail.com

usb 2-1: New USB device strings: Mfr=0, Product=0, SerialNumber=0
usb 2-1: config 0 descriptor??
smsc75xx v1.0.0
==================================================================
BUG: KMSAN: uninit-value in smsc75xx_wait_eeprom+0x1fb/0x3d0  
drivers/net/usb/smsc75xx.c:307
CPU: 1 PID: 10983 Comm: kworker/1:5 Not tainted 5.3.0-rc3+ #16
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_eeprom+0x1fb/0x3d0 drivers/net/usb/smsc75xx.c:307
  smsc75xx_read_eeprom+0x3c2/0x920 drivers/net/usb/smsc75xx.c:364
  smsc75xx_init_mac_address drivers/net/usb/smsc75xx.c:771 [inline]
  smsc75xx_bind+0x675/0x12d0 drivers/net/usb/smsc75xx.c:1489
  usbnet_probe+0x10ae/0x3960 drivers/net/usb/usbnet.c:1722
  usb_probe_interface+0xd19/0x1310 drivers/usb/core/driver.c:361
  really_probe+0x1373/0x1dc0 drivers/base/dd.c:552
  driver_probe_device+0x1ba/0x510 drivers/base/dd.c:709
  __device_attach_driver+0x5b8/0x790 drivers/base/dd.c:816
  bus_for_each_drv+0x28e/0x3b0 drivers/base/bus.c:454
  __device_attach+0x489/0x750 drivers/base/dd.c:882
  device_initial_probe+0x4a/0x60 drivers/base/dd.c:929
  bus_probe_device+0x131/0x390 drivers/base/bus.c:514
  device_add+0x25b5/0x2df0 drivers/base/core.c:2114
  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+0x1373/0x1dc0 drivers/base/dd.c:552
  driver_probe_device+0x1ba/0x510 drivers/base/dd.c:709
  __device_attach_driver+0x5b8/0x790 drivers/base/dd.c:816
  bus_for_each_drv+0x28e/0x3b0 drivers/base/bus.c:454
  __device_attach+0x489/0x750 drivers/base/dd.c:882
  device_initial_probe+0x4a/0x60 drivers/base/dd.c:929
  bus_probe_device+0x131/0x390 drivers/base/bus.c:514
  device_add+0x25b5/0x2df0 drivers/base/core.c:2114
  usb_new_device+0x23e5/0x2fb0 drivers/usb/core/hub.c:2536
  hub_port_connect drivers/usb/core/hub.c:5098 [inline]
  hub_port_connect_change drivers/usb/core/hub.c:5213 [inline]
  port_event drivers/usb/core/hub.c:5359 [inline]
  hub_event+0x581d/0x72f0 drivers/usb/core/hub.c:5441
  process_one_work+0x1572/0x1ef0 kernel/workqueue.c:2269
  worker_thread+0x111b/0x2460 kernel/workqueue.c:2415
  kthread+0x4b5/0x4f0 kernel/kthread.c:256
  ret_from_fork+0x35/0x40 arch/x86/entry/entry_64.S:355

Local variable description: ----buf.i.i@smsc75xx_wait_eeprom
Variable was created at:
  __smsc75xx_read_reg drivers/net/usb/smsc75xx.c:83 [inline]
  smsc75xx_read_reg drivers/net/usb/smsc75xx.c:147 [inline]
  smsc75xx_wait_eeprom+0xb6/0x3d0 drivers/net/usb/smsc75xx.c:301
  smsc75xx_read_eeprom+0x3c2/0x920 drivers/net/usb/smsc75xx.c:364
==================================================================


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