KMSAN: uninit-value in __tipc_nl_compat_dumpit

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    5ef742ba net: kasan: kmsan: support CONFIG_GENERIC_CSUM on..
git tree:       https://github.com/google/kmsan.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=11b40861e00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=8fd289db07d24f0c
dashboard link: https://syzkaller.appspot.com/bug?extid=b1fd2bf2c89d8407e15f
compiler:       clang version 9.0.0 (/home/glider/llvm/clang  
80fee25776c2fb61e74c1ecb1a523375c2500b69)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=13f45aeae00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=17560232e00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+b1fd2bf2c89d8407e15f@xxxxxxxxxxxxxxxxxxxxxxxxx

=====================================================
BUG: KMSAN: uninit-value in __nlmsg_parse include/net/netlink.h:661 [inline]
BUG: KMSAN: uninit-value in nlmsg_parse_deprecated  
include/net/netlink.h:706 [inline]
BUG: KMSAN: uninit-value in __tipc_nl_compat_dumpit+0x553/0x11e0  
net/tipc/netlink_compat.c:215
CPU: 0 PID: 12425 Comm: syz-executor062 Not tainted 5.5.0-rc1-syzkaller #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+0x1c9/0x220 lib/dump_stack.c:118
 kmsan_report+0x128/0x220 mm/kmsan/kmsan_report.c:108
 __msan_warning+0x57/0xa0 mm/kmsan/kmsan_instr.c:245
 __nlmsg_parse include/net/netlink.h:661 [inline]
 nlmsg_parse_deprecated include/net/netlink.h:706 [inline]
 __tipc_nl_compat_dumpit+0x553/0x11e0 net/tipc/netlink_compat.c:215
 tipc_nl_compat_dumpit+0x761/0x910 net/tipc/netlink_compat.c:308
 tipc_nl_compat_handle net/tipc/netlink_compat.c:1252 [inline]
 tipc_nl_compat_recv+0x12e9/0x2870 net/tipc/netlink_compat.c:1311
 genl_family_rcv_msg_doit net/netlink/genetlink.c:672 [inline]
 genl_family_rcv_msg net/netlink/genetlink.c:717 [inline]
 genl_rcv_msg+0x1dd0/0x23a0 net/netlink/genetlink.c:734
 netlink_rcv_skb+0x431/0x620 net/netlink/af_netlink.c:2477
 genl_rcv+0x63/0x80 net/netlink/genetlink.c:745
 netlink_unicast_kernel net/netlink/af_netlink.c:1302 [inline]
 netlink_unicast+0xfa0/0x1100 net/netlink/af_netlink.c:1328
 netlink_sendmsg+0x11f0/0x1480 net/netlink/af_netlink.c:1917
 sock_sendmsg_nosec net/socket.c:639 [inline]
 sock_sendmsg net/socket.c:659 [inline]
 ____sys_sendmsg+0x1362/0x13f0 net/socket.c:2330
 ___sys_sendmsg net/socket.c:2384 [inline]
 __sys_sendmsg+0x4f0/0x5e0 net/socket.c:2417
 __do_sys_sendmsg net/socket.c:2426 [inline]
 __se_sys_sendmsg+0x97/0xb0 net/socket.c:2424
 __x64_sys_sendmsg+0x4a/0x70 net/socket.c:2424
 do_syscall_64+0xb6/0x160 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x444179
Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 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 1b d8 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffd2d6409c8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00000000004002e0 RCX: 0000000000444179
RDX: 0000000000000000 RSI: 0000000020000140 RDI: 0000000000000003
RBP: 00000000006ce018 R08: 0000000000000000 R09: 00000000004002e0
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000401e20
R13: 0000000000401eb0 R14: 0000000000000000 R15: 0000000000000000

Uninit was created at:
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:149 [inline]
 kmsan_internal_poison_shadow+0x5c/0x110 mm/kmsan/kmsan.c:132
 kmsan_slab_alloc+0x8a/0xe0 mm/kmsan/kmsan_hooks.c:86
 slab_alloc_node mm/slub.c:2774 [inline]
 __kmalloc_node_track_caller+0xe47/0x11f0 mm/slub.c:4382
 __kmalloc_reserve net/core/skbuff.c:141 [inline]
 __alloc_skb+0x309/0xa50 net/core/skbuff.c:209
 alloc_skb include/linux/skbuff.h:1049 [inline]
 nlmsg_new include/net/netlink.h:888 [inline]
 tipc_nl_compat_dumpit+0x6e4/0x910 net/tipc/netlink_compat.c:301
 tipc_nl_compat_handle net/tipc/netlink_compat.c:1252 [inline]
 tipc_nl_compat_recv+0x12e9/0x2870 net/tipc/netlink_compat.c:1311
 genl_family_rcv_msg_doit net/netlink/genetlink.c:672 [inline]
 genl_family_rcv_msg net/netlink/genetlink.c:717 [inline]
 genl_rcv_msg+0x1dd0/0x23a0 net/netlink/genetlink.c:734
 netlink_rcv_skb+0x431/0x620 net/netlink/af_netlink.c:2477
 genl_rcv+0x63/0x80 net/netlink/genetlink.c:745
 netlink_unicast_kernel net/netlink/af_netlink.c:1302 [inline]
 netlink_unicast+0xfa0/0x1100 net/netlink/af_netlink.c:1328
 netlink_sendmsg+0x11f0/0x1480 net/netlink/af_netlink.c:1917
 sock_sendmsg_nosec net/socket.c:639 [inline]
 sock_sendmsg net/socket.c:659 [inline]
 ____sys_sendmsg+0x1362/0x13f0 net/socket.c:2330
 ___sys_sendmsg net/socket.c:2384 [inline]
 __sys_sendmsg+0x4f0/0x5e0 net/socket.c:2417
 __do_sys_sendmsg net/socket.c:2426 [inline]
 __se_sys_sendmsg+0x97/0xb0 net/socket.c:2424
 __x64_sys_sendmsg+0x4a/0x70 net/socket.c:2424
 do_syscall_64+0xb6/0x160 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
=====================================================


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxxx

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches