KMSAN: uninit-value in __tipc_nl_bearer_enable

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    0a602458c72c kmsan: random: another take at unpoisoning CR..
git tree:       kmsan
console output: https://syzkaller.appspot.com/x/log.txt?x=125b568b400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=9b071100dcf8e641
dashboard link: https://syzkaller.appspot.com/bug?extid=e820fdc8ce362f2dea51
compiler:       clang version 8.0.0 (trunk 348261)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=139c6347400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+e820fdc8ce362f2dea51@xxxxxxxxxxxxxxxxxxxxxxxxx

8021q: adding VLAN 0 to HW filter on device team0
8021q: adding VLAN 0 to HW filter on device team0
8021q: adding VLAN 0 to HW filter on device team0
8021q: adding VLAN 0 to HW filter on device team0
==================================================================
BUG: KMSAN: uninit-value in strncpy+0x265/0x590 lib/string.c:119
CPU: 0 PID: 8068 Comm: syz-executor5 Not tainted 4.20.0-rc5+ #2
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+0x1c9/0x220 lib/dump_stack.c:113
 kmsan_report+0x12d/0x290 mm/kmsan/kmsan.c:682
 __msan_warning+0x76/0xc0 mm/kmsan/kmsan_instr.c:316
 strncpy+0x265/0x590 lib/string.c:119
 bearer_name_validate net/tipc/bearer.c:141 [inline]
 tipc_enable_bearer net/tipc/bearer.c:246 [inline]
 __tipc_nl_bearer_enable+0x674/0x1da0 net/tipc/bearer.c:897
 tipc_nl_bearer_enable+0x6c/0xb0 net/tipc/bearer.c:905
 genl_family_rcv_msg net/netlink/genetlink.c:601 [inline]
 genl_rcv_msg+0x185f/0x1a60 net/netlink/genetlink.c:626
 netlink_rcv_skb+0x444/0x640 net/netlink/af_netlink.c:2477
 genl_rcv+0x63/0x80 net/netlink/genetlink.c:637
 netlink_unicast_kernel net/netlink/af_netlink.c:1310 [inline]
 netlink_unicast+0xf80/0x1060 net/netlink/af_netlink.c:1336
 netlink_sendmsg+0x129d/0x1310 net/netlink/af_netlink.c:1917
 sock_sendmsg_nosec net/socket.c:621 [inline]
 sock_sendmsg net/socket.c:631 [inline]
 ___sys_sendmsg+0xdbc/0x11d0 net/socket.c:2116
 __sys_sendmsg net/socket.c:2154 [inline]
 __do_sys_sendmsg net/socket.c:2163 [inline]
 __se_sys_sendmsg+0x305/0x460 net/socket.c:2161
 __x64_sys_sendmsg+0x4a/0x70 net/socket.c:2161
 do_syscall_64+0xcd/0x110 arch/x86/entry/common.c:291
 entry_SYSCALL_64_after_hwframe+0x63/0xe7
RIP: 0033:0x457669
Code: fd b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7  
48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff  
ff 0f 83 cb b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f04f1c0ac78 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000457669
RDX: 0000000000000000 RSI: 00000000200008c0 RDI: 0000000000000003
RBP: 000000000072bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f04f1c0b6d4
R13: 00000000004c421b R14: 00000000004d7160 R15: 00000000ffffffff

Uninit was created at:
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:247 [inline]
 kmsan_internal_poison_shadow+0x92/0x150 mm/kmsan/kmsan.c:170
 kmsan_kmalloc+0xa1/0x100 mm/kmsan/kmsan_hooks.c:179
 kmsan_slab_alloc+0xe/0x10 mm/kmsan/kmsan_hooks.c:188
 slab_post_alloc_hook mm/slab.h:446 [inline]
 slab_alloc_node mm/slub.c:2759 [inline]
 __kmalloc_node_track_caller+0xf06/0x1120 mm/slub.c:4383
 __kmalloc_reserve net/core/skbuff.c:137 [inline]
 __alloc_skb+0x318/0xa40 net/core/skbuff.c:205
 alloc_skb include/linux/skbuff.h:998 [inline]
 netlink_alloc_large_skb net/netlink/af_netlink.c:1182 [inline]
 netlink_sendmsg+0xba0/0x1310 net/netlink/af_netlink.c:1892
 sock_sendmsg_nosec net/socket.c:621 [inline]
 sock_sendmsg net/socket.c:631 [inline]
 ___sys_sendmsg+0xdbc/0x11d0 net/socket.c:2116
 __sys_sendmsg net/socket.c:2154 [inline]
 __do_sys_sendmsg net/socket.c:2163 [inline]
 __se_sys_sendmsg+0x305/0x460 net/socket.c:2161
 __x64_sys_sendmsg+0x4a/0x70 net/socket.c:2161
 do_syscall_64+0xcd/0x110 arch/x86/entry/common.c:291
 entry_SYSCALL_64_after_hwframe+0x63/0xe7
==================================================================


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