KMSAN: uninit-value in pppoe_connect

[syzbot]

Hello,

syzbot hit the following crash on  
https://github.com/google/kmsan.git/master commit
a7f95e9c8a95e9fbb388c3999b61a17667cd3bbe (Sat Apr 21 13:50:22 2018 +0000)
kmsan: disable assembly checksums
syzbot dashboard link:  
https://syzkaller.appspot.com/bug?extid=4f03bdf92fdf9ef5ddab

So far this crash happened 2 times on  
https://github.com/google/kmsan.git/master.
Unfortunately, I don't have any reproducer for this crash yet.
Raw console output:  
https://syzkaller.appspot.com/x/log.txt?id=5233317381144576
Kernel config: https://syzkaller.appspot.com/x/.config?id=328654897048964367
compiler: clang version 7.0.0 (trunk 329391)

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+4f03bdf92fdf9ef5ddab@xxxxxxxxxxxxxxxxxxxxxxxxx
It will help syzbot understand when the bug is fixed. See footer for  
details.
If you forward the report, please keep this part and the footer.

==================================================================
BUG: KMSAN: uninit-value in pppoe_connect+0xe9a/0x2360  
drivers/net/ppp/pppoe.c:662
CPU: 1 PID: 8338 Comm: syz-executor2 Not tainted 4.16.0+ #85
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x185/0x1d0 lib/dump_stack.c:53
 kmsan_report+0x142/0x240 mm/kmsan/kmsan.c:1067
 __msan_warning_32+0x6c/0xb0 mm/kmsan/kmsan_instr.c:683
 pppoe_connect+0xe9a/0x2360 drivers/net/ppp/pppoe.c:662
 SYSC_connect+0x41a/0x510 net/socket.c:1639
 SyS_connect+0x54/0x80 net/socket.c:1620
 do_syscall_64+0x309/0x430 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x3d/0xa2
RIP: 0033:0x455389
RSP: 002b:00007f5c253ecc68 EFLAGS: 00000246 ORIG_RAX: 000000000000002a
RAX: ffffffffffffffda RBX: 00007f5c253ed6d4 RCX: 0000000000455389
RDX: 0000000000000001 RSI: 0000000020000040 RDI: 0000000000000013
RBP: 000000000072bea0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000063 R14: 00000000006f39e8 R15: 0000000000000000

Local variable description: ----address@SYSC_connect
Variable was created at:
 SYSC_connect+0x6f/0x510 net/socket.c:1622
 SyS_connect+0x54/0x80 net/socket.c:1620
==================================================================


---
This bug is generated by a dumb bot. It may contain errors.
See https://goo.gl/tpsmEJ for details.
Direct all questions to syzkaller@xxxxxxxxxxxxxxxxx

syzbot will keep track of this bug report.
If you forgot to add the Reported-by tag, once the fix for this bug is  
merged
into any tree, please reply to this email with:
#syz fix: exact-commit-title
To mark this as a duplicate of another syzbot report, please reply with:
#syz dup: exact-subject-of-another-report
If it's a one-off invalid bug report, please reply with:
#syz invalid
Note: if the crash happens again, it will cause creation of a new bug  
report.
Note: all commands must start from beginning of the line in the email body.