Re: KMSAN: uninit-value in tipc_node_get_mtu

[syzbot]

syzbot has found reproducer for the following crash on  
https://github.com/google/kmsan.git/master commit
e2ab7e8abba47a2f2698216258e5d8727ae58717 (Fri Apr 6 16:24:31 2018 +0000)
kmsan: temporarily disable visitAsmInstruction() to help syzbot
syzbot dashboard link:  
https://syzkaller.appspot.com/bug?extid=b0975ce9355b347c1546

So far this crash happened 16 times on  
https://github.com/google/kmsan.git/master.
C reproducer: https://syzkaller.appspot.com/x/repro.c?id=5297557005664256
syzkaller reproducer:  
https://syzkaller.appspot.com/x/repro.syz?id=4600034989441024
Raw console output:  
https://syzkaller.appspot.com/x/log.txt?id=5107856890134528
Kernel config:  
https://syzkaller.appspot.com/x/.config?id=6627248707860932248
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+b0975ce9355b347c1546@xxxxxxxxxxxxxxxxxxxxxxxxx
It will help syzbot understand when the bug is fixed.

==================================================================
BUG: KMSAN: uninit-value in tipc_node_find net/tipc/node.c:236 [inline]
BUG: KMSAN: uninit-value in tipc_node_get_mtu+0x200/0x7a0  
net/tipc/node.c:185
CPU: 1 PID: 3571 Comm: syzkaller770798 Not tainted 4.16.0+ #82
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:676
 tipc_node_find net/tipc/node.c:236 [inline]
 tipc_node_get_mtu+0x200/0x7a0 net/tipc/node.c:185
 __tipc_sendmsg+0x1b32/0x41c0 net/tipc/socket.c:1364
 tipc_sendmsg+0xeb/0x140 net/tipc/socket.c:1265
 sock_sendmsg_nosec net/socket.c:630 [inline]
 sock_sendmsg net/socket.c:640 [inline]
 ___sys_sendmsg+0xec0/0x1310 net/socket.c:2046
 __sys_sendmsg net/socket.c:2080 [inline]
 SYSC_sendmsg+0x2a3/0x3d0 net/socket.c:2091
 SyS_sendmsg+0x54/0x80 net/socket.c:2087
 do_syscall_64+0x309/0x430 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x3d/0xa2
RIP: 0033:0x43fd49
RSP: 002b:00007ffd0061aba8 EFLAGS: 00000213 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 000000000043fd49
RDX: 0000000000000000 RSI: 000000002095ffc8 RDI: 0000000000000003
RBP: 00000000006ca018 R08: 00000000004002c8 R09: 00000000004002c8
R10: 00000000004002c8 R11: 0000000000000213 R12: 0000000000401670
R13: 0000000000401700 R14: 0000000000000000 R15: 0000000000000000

Local variable description: ----dnode@__tipc_sendmsg
Variable was created at:
 __tipc_sendmsg+0x20c/0x41c0 net/tipc/socket.c:1272
 tipc_sendmsg+0xeb/0x140 net/tipc/socket.c:1265
==================================================================
Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 3571 Comm: syzkaller770798 Tainted: G    B            4.16.0+  
#82
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
 panic+0x39d/0x940 kernel/panic.c:183
 kmsan_report+0x238/0x240 mm/kmsan/kmsan.c:1083
 __msan_warning_32+0x6c/0xb0 mm/kmsan/kmsan_instr.c:676
 tipc_node_find net/tipc/node.c:236 [inline]
 tipc_node_get_mtu+0x200/0x7a0 net/tipc/node.c:185
 __tipc_sendmsg+0x1b32/0x41c0 net/tipc/socket.c:1364
 tipc_sendmsg+0xeb/0x140 net/tipc/socket.c:1265
 sock_sendmsg_nosec net/socket.c:630 [inline]
 sock_sendmsg net/socket.c:640 [inline]
 ___sys_sendmsg+0xec0/0x1310 net/socket.c:2046
 __sys_sendmsg net/socket.c:2080 [inline]
 SYSC_sendmsg+0x2a3/0x3d0 net/socket.c:2091
 SyS_sendmsg+0x54/0x80 net/socket.c:2087
 do_syscall_64+0x309/0x430 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x3d/0xa2
RIP: 0033:0x43fd49
RSP: 002b:00007ffd0061aba8 EFLAGS: 00000213 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 000000000043fd49
RDX: 0000000000000000 RSI: 000000002095ffc8 RDI: 0000000000000003
RBP: 00000000006ca018 R08: 00000000004002c8 R09: 00000000004002c8
R10: 00000000004002c8 R11: 0000000000000213 R12: 0000000000401670
R13: 0000000000401700 R14: 0000000000000000 R15: 0000000000000000
Dumping ftrace buffer:
   (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..