==================================================================
BUG: KMSAN: uninit-value in _decode_session6+0x645/0x1650 net/ipv6/xfrm6_policy.c:149
CPU: 0 PID: 6810 Comm: syz-executor0 Not tainted 4.19.0-rc4+ #58
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+0x2f6/0x430 lib/dump_stack.c:113
 kmsan_report+0x183/0x2b0 mm/kmsan/kmsan.c:917
 __msan_warning+0x70/0xc0 mm/kmsan/kmsan_instr.c:500
 _decode_session6+0x645/0x1650 net/ipv6/xfrm6_policy.c:149
 __xfrm_decode_session+0x156/0x200 net/xfrm/xfrm_policy.c:2299
 xfrm_decode_session_reverse include/net/xfrm.h:1239 [inline]
 icmpv6_route_lookup net/ipv6/icmp.c:372 [inline]
 icmp6_send+0x2d01/0x3840 net/ipv6/icmp.c:551
 icmpv6_send+0xe5/0x110 net/ipv6/ip6_icmp.c:43
 ip6_fragment+0xc6a/0x5200 net/ipv6/ip6_output.c:861
 ip6_finish_output+0xacb/0xc70 net/ipv6/ip6_output.c:152
 NF_HOOK_COND include/linux/netfilter.h:276 [inline]
 ip6_output+0x572/0x6a0 net/ipv6/ip6_output.c:171
 dst_output include/net/dst.h:444 [inline]
 ip6_local_out+0x164/0x1d0 net/ipv6/output_core.c:176
 ip6_send_skb net/ipv6/ip6_output.c:1697 [inline]
 ip6_push_pending_frames+0x218/0x4d0 net/ipv6/ip6_output.c:1717
 rawv6_push_pending_frames net/ipv6/raw.c:616 [inline]
 rawv6_sendmsg+0x45f7/0x5680 net/ipv6/raw.c:933
 inet_sendmsg+0x4c5/0x7d0 net/ipv4/af_inet.c:798
 sock_sendmsg_nosec net/socket.c:621 [inline]
 sock_sendmsg net/socket.c:631 [inline]
 sock_write_iter+0x3b8/0x470 net/socket.c:900
 call_write_iter include/linux/fs.h:1808 [inline]
 new_sync_write fs/read_write.c:474 [inline]
 __vfs_write+0x7ae/0xa50 fs/read_write.c:487
 vfs_write+0x495/0x8e0 fs/read_write.c:549
 ksys_write fs/read_write.c:598 [inline]
 __do_sys_write fs/read_write.c:610 [inline]
 __se_sys_write+0x173/0x350 fs/read_write.c:607
 __x64_sys_write+0x4a/0x70 fs/read_write.c:607
 do_syscall_64+0xb8/0x100 arch/x86/entry/common.c:291
 entry_SYSCALL_64_after_hwframe+0x63/0xe7
RIP: 0033:0x457579
Code: 1d b4 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 eb b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f1dfd80bc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000457579
RDX: 000000000000058d RSI: 0000000020000900 RDI: 0000000000000004
RBP: 000000000072bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f1dfd80c6d4
R13: 00000000004c5516 R14: 00000000004d8e20 R15: 00000000ffffffff

Uninit was created at:
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:255 [inline]
 kmsan_internal_poison_shadow+0xb8/0x1b0 mm/kmsan/kmsan.c:180
 kmsan_kmalloc+0x98/0x100 mm/kmsan/kmsan_hooks.c:91
 kmsan_slab_alloc+0x10/0x20 mm/kmsan/kmsan_hooks.c:100
 slab_post_alloc_hook mm/slab.h:446 [inline]
 slab_alloc_node mm/slub.c:2718 [inline]
 __kmalloc_node_track_caller+0xb55/0x1380 mm/slub.c:4351
 __kmalloc_reserve net/core/skbuff.c:138 [inline]
 __alloc_skb+0x40d/0xe50 net/core/skbuff.c:206
 alloc_skb include/linux/skbuff.h:996 [inline]
 __ip6_append_data+0x3c5e/0x51a0 net/ipv6/ip6_output.c:1427
 ip6_append_data+0x3d8/0x670 net/ipv6/ip6_output.c:1589
 rawv6_sendmsg+0x2ac7/0x5680 net/ipv6/raw.c:926
 inet_sendmsg+0x4c5/0x7d0 net/ipv4/af_inet.c:798
 sock_sendmsg_nosec net/socket.c:621 [inline]
 sock_sendmsg net/socket.c:631 [inline]
 sock_write_iter+0x3b8/0x470 net/socket.c:900
 call_write_iter include/linux/fs.h:1808 [inline]
 new_sync_write fs/read_write.c:474 [inline]
 __vfs_write+0x7ae/0xa50 fs/read_write.c:487
 vfs_write+0x495/0x8e0 fs/read_write.c:549
 ksys_write fs/read_write.c:598 [inline]
 __do_sys_write fs/read_write.c:610 [inline]
 __se_sys_write+0x173/0x350 fs/read_write.c:607
 __x64_sys_write+0x4a/0x70 fs/read_write.c:607
 do_syscall_64+0xb8/0x100 arch/x86/entry/common.c:291
 entry_SYSCALL_64_after_hwframe+0x63/0xe7
==================================================================