=====================================================
BUG: KMSAN: uninit-value in __netif_receive_skb_core+0x3f45/0x6520 net/core/dev.c:5197
CPU: 0 PID: 23463 Comm: syz-executor.5 Not tainted 5.8.0-rc5-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+0x21c/0x280 lib/dump_stack.c:118
 kmsan_report+0xf7/0x1e0 mm/kmsan/kmsan_report.c:121
 __msan_warning+0x58/0xa0 mm/kmsan/kmsan_instr.c:215
 __netif_receive_skb_core+0x3f45/0x6520 net/core/dev.c:5197
 __netif_receive_skb_one_core net/core/dev.c:5279 [inline]
 __netif_receive_skb+0x164/0x670 net/core/dev.c:5395
 netif_receive_skb_internal+0x33c/0x3b0 net/core/dev.c:5497
 netif_receive_skb+0x1c1/0x360 net/core/dev.c:5556
 tun_rx_batched include/linux/skbuff.h:4327 [inline]
 tun_get_user+0x63f6/0x66e0 drivers/net/tun.c:1972
 tun_chr_write_iter+0x1f2/0x360 drivers/net/tun.c:2001
 call_write_iter include/linux/fs.h:1908 [inline]
 new_sync_write fs/read_write.c:503 [inline]
 vfs_write+0xf9a/0x17c0 fs/read_write.c:578
 ksys_write+0x275/0x500 fs/read_write.c:631
 __do_sys_write fs/read_write.c:643 [inline]
 __se_sys_write+0x92/0xb0 fs/read_write.c:640
 __x64_sys_write+0x4a/0x70 fs/read_write.c:640
 do_syscall_64+0xad/0x160 arch/x86/entry/common.c:386
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45d4d9
Code: Bad RIP value.
RSP: 002b:00007f7dcd6fec78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000039980 RCX: 000000000045d4d9
RDX: 000000000000fdef RSI: 0000000020000140 RDI: 0000000000000003
RBP: 000000000118d0c0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000118d08c
R13: 000000000169fb6f R14: 00007f7dcd6ff9c0 R15: 000000000118d08c

Uninit was stored to memory at:
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:144 [inline]
 kmsan_internal_chain_origin+0xad/0x130 mm/kmsan/kmsan.c:310
 __msan_chain_origin+0x50/0x90 mm/kmsan/kmsan_instr.c:165
 vlan_set_encap_proto include/linux/if_vlan.h:656 [inline]
 skb_vlan_untag+0x7e7/0xf70 net/core/skbuff.c:5431
 __netif_receive_skb_core+0xa4d/0x6520 net/core/dev.c:5119
 __netif_receive_skb_one_core net/core/dev.c:5279 [inline]
 __netif_receive_skb+0x164/0x670 net/core/dev.c:5395
 netif_receive_skb_internal+0x33c/0x3b0 net/core/dev.c:5497
 netif_receive_skb+0x1c1/0x360 net/core/dev.c:5556
 tun_rx_batched include/linux/skbuff.h:4327 [inline]
 tun_get_user+0x63f6/0x66e0 drivers/net/tun.c:1972
 tun_chr_write_iter+0x1f2/0x360 drivers/net/tun.c:2001
 call_write_iter include/linux/fs.h:1908 [inline]
 new_sync_write fs/read_write.c:503 [inline]
 vfs_write+0xf9a/0x17c0 fs/read_write.c:578
 ksys_write+0x275/0x500 fs/read_write.c:631
 __do_sys_write fs/read_write.c:643 [inline]
 __se_sys_write+0x92/0xb0 fs/read_write.c:640
 __x64_sys_write+0x4a/0x70 fs/read_write.c:640
 do_syscall_64+0xad/0x160 arch/x86/entry/common.c:386
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Uninit was created at:
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:144 [inline]
 kmsan_internal_poison_shadow+0x66/0xd0 mm/kmsan/kmsan.c:127
 kmsan_slab_alloc+0x8a/0xe0 mm/kmsan/kmsan_hooks.c:80
 slab_alloc_node mm/slub.c:2839 [inline]
 __kmalloc_node_track_caller+0xeab/0x12e0 mm/slub.c:4478
 __kmalloc_reserve net/core/skbuff.c:142 [inline]
 __alloc_skb+0x35f/0xb30 net/core/skbuff.c:210
 alloc_skb include/linux/skbuff.h:1083 [inline]
 alloc_skb_with_frags+0x1f2/0xc10 net/core/skbuff.c:5770
 sock_alloc_send_pskb+0xc83/0xe50 net/core/sock.c:2356
 tun_alloc_skb drivers/net/tun.c:1494 [inline]
 tun_get_user+0x1a32/0x66e0 drivers/net/tun.c:1811
 tun_chr_write_iter+0x1f2/0x360 drivers/net/tun.c:2001
 call_write_iter include/linux/fs.h:1908 [inline]
 new_sync_write fs/read_write.c:503 [inline]
 vfs_write+0xf9a/0x17c0 fs/read_write.c:578
 ksys_write+0x275/0x500 fs/read_write.c:631
 __do_sys_write fs/read_write.c:643 [inline]
 __se_sys_write+0x92/0xb0 fs/read_write.c:640
 __x64_sys_write+0x4a/0x70 fs/read_write.c:640
 do_syscall_64+0xad/0x160 arch/x86/entry/common.c:386
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
=====================================================