syzbot

syzkaller1: entered promiscuous mode
syzkaller1: entered allmulticast mode
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BUG: KMSAN: uninit-value in __INET_ECN_decapsulate include/net/inet_ecn.h:253 [inline]
BUG: KMSAN: uninit-value in INET_ECN_decapsulate include/net/inet_ecn.h:275 [inline]
BUG: KMSAN: uninit-value in IP_ECN_decapsulate include/net/inet_ecn.h:302 [inline]
BUG: KMSAN: uninit-value in ip_tunnel_rcv+0x1311/0x34f0 net/ipv4/ip_tunnel.c:423
 __INET_ECN_decapsulate include/net/inet_ecn.h:253 [inline]
 INET_ECN_decapsulate include/net/inet_ecn.h:275 [inline]
 IP_ECN_decapsulate include/net/inet_ecn.h:302 [inline]
 ip_tunnel_rcv+0x1311/0x34f0 net/ipv4/ip_tunnel.c:423
 erspan_rcv net/ipv4/ip_gre.c:354 [inline]
 gre_rcv+0x1aad/0x2050 net/ipv4/ip_gre.c:458
 gre_rcv+0x285/0x380 net/ipv4/gre_demux.c:163
 ip_protocol_deliver_rcu+0xb29/0x13d0 net/ipv4/ip_input.c:205
 ip_local_deliver_finish+0x409/0x730 net/ipv4/ip_input.c:239
 NF_HOOK include/linux/netfilter.h:318 [inline]
 ip_local_deliver+0x228/0x4b0 net/ipv4/ip_input.c:260
 dst_input include/net/dst.h:471 [inline]
 ip_rcv_finish+0x4f7/0x5c0 net/ipv4/ip_input.c:454
 NF_HOOK include/linux/netfilter.h:318 [inline]
 ip_rcv+0xcb/0x380 net/ipv4/ip_input.c:574
 __netif_receive_skb_one_core net/core/dev.c:5991 [inline]
 __netif_receive_skb+0x312/0xac0 net/core/dev.c:6104
 netif_receive_skb_internal net/core/dev.c:6190 [inline]
 netif_receive_skb+0x57/0x630 net/core/dev.c:6249
 tun_rx_batched+0x1df/0x980 drivers/net/tun.c:1485
 tun_get_user+0x5028/0x6ca0 drivers/net/tun.c:1950
 tun_chr_write_iter+0x3e9/0x5c0 drivers/net/tun.c:1996
 new_sync_write fs/read_write.c:593 [inline]
 vfs_write+0xbe2/0x15d0 fs/read_write.c:686
 ksys_write fs/read_write.c:738 [inline]
 __do_sys_write fs/read_write.c:749 [inline]
 __se_sys_write fs/read_write.c:746 [inline]
 __x64_sys_write+0x1fb/0x4d0 fs/read_write.c:746
 x64_sys_call+0x3014/0x3e20 arch/x86/include/generated/asm/syscalls_64.h:2
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd9/0x210 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Uninit was created at:
 slab_post_alloc_hook mm/slub.c:4186 [inline]
 slab_alloc_node mm/slub.c:4229 [inline]
 kmem_cache_alloc_node_noprof+0x818/0xf00 mm/slub.c:4281
 kmalloc_reserve+0x13c/0x4b0 net/core/skbuff.c:578
 __alloc_skb+0x347/0x7d0 net/core/skbuff.c:669
 alloc_skb include/linux/skbuff.h:1336 [inline]
 alloc_skb_with_frags+0xc5/0xa60 net/core/skbuff.c:6665
 sock_alloc_send_pskb+0xad8/0xc70 net/core/sock.c:2980
 tun_alloc_skb drivers/net/tun.c:1461 [inline]
 tun_get_user+0x113f/0x6ca0 drivers/net/tun.c:1794
 tun_chr_write_iter+0x3e9/0x5c0 drivers/net/tun.c:1996
 new_sync_write fs/read_write.c:593 [inline]
 vfs_write+0xbe2/0x15d0 fs/read_write.c:686
 ksys_write fs/read_write.c:738 [inline]
 __do_sys_write fs/read_write.c:749 [inline]
 __se_sys_write fs/read_write.c:746 [inline]
 __x64_sys_write+0x1fb/0x4d0 fs/read_write.c:746
 x64_sys_call+0x3014/0x3e20 arch/x86/include/generated/asm/syscalls_64.h:2
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd9/0x210 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

CPU: 0 UID: 0 PID: 6057 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(none) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
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