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BUG: KMSAN: uninit-value in ip_tunnel_rcv+0x13fb/0x3a40
 ip_tunnel_rcv+0x13fb/0x3a40
 __ipgre_rcv+0xaf0/0xe50
 gre_rcv+0x4ca/0x1e50
 gre_rcv+0x323/0x420
 ip_protocol_deliver_rcu+0x643/0xe30
 ip_local_deliver_finish+0x36c/0x500
 ip_local_deliver+0x34c/0x590
 ip_rcv+0x5b2/0x840
 __netif_receive_skb+0x1f1/0x640
 netif_receive_skb_internal+0x1b7/0x3d0
 netif_receive_skb+0x4d/0x360
 tun_rx_batched+0xa93/0xd00
 tun_get_user+0x4344/0x4e90
 tun_chr_write_iter+0x459/0x610
 vfs_write+0x10ab/0x1d40
 ksys_write+0x28f/0x510
 __x64_sys_write+0xdb/0x120
 do_syscall_64+0x3d/0xb0
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Uninit was created at:
 __alloc_pages+0x8ae/0x1040
 alloc_pages+0x98c/0xca0
 skb_page_frag_refill+0x35f/0x8f0
 tun_build_skb+0x244/0x19c0
 tun_get_user+0x1055/0x4e90
 tun_chr_write_iter+0x459/0x610
 vfs_write+0x10ab/0x1d40
 ksys_write+0x28f/0x510
 __x64_sys_write+0xdb/0x120
 do_syscall_64+0x3d/0xb0
 entry_SYSCALL_64_after_hwframe+0x44/0xae

CPU: 1 PID: 3508 Comm: syz-executor343 Not tainted 5.18.0-syzkaller-16253-g2f3064574275 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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