KMSAN: uninit-value in sysfs_format_mac

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    c2453450 kmsan: kcov: prettify the code unpoisoning area->..
git tree:       https://github.com/google/kmsan.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=1342116f600000
kernel config:  https://syzkaller.appspot.com/x/.config?x=3684f3c73f43899a
dashboard link: https://syzkaller.appspot.com/bug?extid=dac45508e04ca7aba764
compiler:       clang version 9.0.0 (/home/glider/llvm/clang  
80fee25776c2fb61e74c1ecb1a523375c2500b69)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11083f9f600000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16c7073b600000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+dac45508e04ca7aba764@xxxxxxxxxxxxxxxxxxxxxxxxx

=====================================================
BUG: KMSAN: uninit-value in hex_string+0x7d8/0x8d0 lib/vsprintf.c:1098
CPU: 0 PID: 12732 Comm: udevd Not tainted 5.4.0-rc3+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x191/0x1f0 lib/dump_stack.c:113
 kmsan_report+0x14a/0x2f0 mm/kmsan/kmsan_report.c:109
 __msan_warning+0x73/0xf0 mm/kmsan/kmsan_instr.c:245
 hex_string+0x7d8/0x8d0 lib/vsprintf.c:1098
 pointer+0xbfe/0x1d10 lib/vsprintf.c:2136
 vsnprintf+0x1c0c/0x3210 lib/vsprintf.c:2514
 vscnprintf lib/vsprintf.c:2613 [inline]
 scnprintf+0x235/0x300 lib/vsprintf.c:2667
 sysfs_format_mac+0xde/0x100 net/ethernet/eth.c:444
 address_show+0x159/0x1d0 net/core/net-sysfs.c:150
 dev_attr_show+0xd8/0x1e0 drivers/base/core.c:967
 sysfs_kf_seq_show+0x434/0x7b0 fs/sysfs/file.c:60
 kernfs_seq_show+0x164/0x1e0 fs/kernfs/file.c:167
 seq_read+0xac6/0x1d90 fs/seq_file.c:229
 kernfs_fop_read+0x2c3/0x9a0 fs/kernfs/file.c:251
 __vfs_read+0x1a9/0xc90 fs/read_write.c:425
 vfs_read+0x359/0x6f0 fs/read_write.c:461
 ksys_read+0x265/0x430 fs/read_write.c:587
 __do_sys_read fs/read_write.c:597 [inline]
 __se_sys_read+0x92/0xb0 fs/read_write.c:595
 __x64_sys_read+0x4a/0x70 fs/read_write.c:595
 do_syscall_64+0xb6/0x160 arch/x86/entry/common.c:291
 entry_SYSCALL_64_after_hwframe+0x63/0xe7
RIP: 0033:0x7f90a0b58310
Code: 73 01 c3 48 8b 0d 28 4b 2b 00 31 d2 48 29 c2 64 89 11 48 83 c8 ff eb  
ea 90 90 83 3d e5 a2 2b 00 00 75 10 b8 00 00 00 00 0f 05 <48> 3d 01 f0 ff  
ff 73 31 c3 48 83 ec 08 e8 6e 8a 01 00 48 89 04 24
RSP: 002b:00007ffdd54d89d8 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 00007f90a0b58310
RDX: 0000000000001000 RSI: 00007ffdd54d8e80 RDI: 0000000000000005
RBP: 00007ffdd54d9fb0 R08: 00007ffdd54d9fb0 R09: 00007f90a0bae7d0
R10: 342f346273752f33 R11: 0000000000000246 R12: 00000000024071f0
R13: 00000000024072e0 R14: 0000000000000001 R15: 0000000002410159

Uninit was stored to memory at:
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:150 [inline]
 kmsan_internal_chain_origin+0xbd/0x170 mm/kmsan/kmsan.c:317
 kmsan_memcpy_memmove_metadata+0x25c/0x2e0 mm/kmsan/kmsan.c:253
 kmsan_memcpy_metadata+0xb/0x10 mm/kmsan/kmsan.c:273
 __msan_memcpy+0x56/0x70 mm/kmsan/kmsan_instr.c:129
 set_ethernet_addr drivers/net/usb/rtl8150.c:282 [inline]
 rtl8150_probe+0x1143/0x14a0 drivers/net/usb/rtl8150.c:912
 usb_probe_interface+0xd19/0x1310 drivers/usb/core/driver.c:361
 really_probe+0xd91/0x1f90 drivers/base/dd.c:552
 driver_probe_device+0x1ba/0x510 drivers/base/dd.c:721
 __device_attach_driver+0x5b8/0x790 drivers/base/dd.c:828
 bus_for_each_drv+0x28e/0x3b0 drivers/base/bus.c:430
 __device_attach+0x489/0x750 drivers/base/dd.c:894
 device_initial_probe+0x4a/0x60 drivers/base/dd.c:941
 bus_probe_device+0x131/0x390 drivers/base/bus.c:490
 device_add+0x25b5/0x2df0 drivers/base/core.c:2201
 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+0xd91/0x1f90 drivers/base/dd.c:552
 driver_probe_device+0x1ba/0x510 drivers/base/dd.c:721
 __device_attach_driver+0x5b8/0x790 drivers/base/dd.c:828
 bus_for_each_drv+0x28e/0x3b0 drivers/base/bus.c:430
 __device_attach+0x489/0x750 drivers/base/dd.c:894
 device_initial_probe+0x4a/0x60 drivers/base/dd.c:941
 bus_probe_device+0x131/0x390 drivers/base/bus.c:490
 device_add+0x25b5/0x2df0 drivers/base/core.c:2201
 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: ----node_id.i@rtl8150_probe
Variable was created at:
 get_registers drivers/net/usb/rtl8150.c:911 [inline]
 set_ethernet_addr drivers/net/usb/rtl8150.c:281 [inline]
 rtl8150_probe+0xdc8/0x14a0 drivers/net/usb/rtl8150.c:912
 get_registers drivers/net/usb/rtl8150.c:911 [inline]
 set_ethernet_addr drivers/net/usb/rtl8150.c:281 [inline]
 rtl8150_probe+0xdc8/0x14a0 drivers/net/usb/rtl8150.c:912
=====================================================


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