syzbot

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BUG: KCSAN: data-race in igmp_rcv / igmp_rcv

write to 0xffff8881187eea50 of 8 bytes by task 13667 on cpu 0:
 igmp_heard_query net/ipv4/igmp.c:1012 [inline]
 igmp_rcv+0x1279/0x14f0 net/ipv4/igmp.c:1103
 ip_protocol_deliver_rcu+0x420/0x780 net/ipv4/ip_input.c:205
 ip_local_deliver_finish+0x184/0x220 net/ipv4/ip_input.c:233
 NF_HOOK include/linux/netfilter.h:314 [inline]
 ip_local_deliver+0xe8/0x1c0 net/ipv4/ip_input.c:254
 dst_input include/net/dst.h:469 [inline]
 ip_rcv_finish+0x188/0x1a0 net/ipv4/ip_input.c:447
 NF_HOOK include/linux/netfilter.h:314 [inline]
 ip_rcv+0x62/0x140 net/ipv4/ip_input.c:567
 __netif_receive_skb_one_core net/core/dev.c:5887 [inline]
 __netif_receive_skb+0xff/0x270 net/core/dev.c:6000
 netif_receive_skb_internal net/core/dev.c:6086 [inline]
 netif_receive_skb+0x4b/0x2e0 net/core/dev.c:6145
 tun_rx_batched+0xfc/0x430 drivers/net/tun.c:1485
 tun_get_user+0x1e07/0x24d0 drivers/net/tun.c:1938
 tun_chr_write_iter+0x15e/0x210 drivers/net/tun.c:1984
 new_sync_write fs/read_write.c:591 [inline]
 vfs_write+0x49d/0x8d0 fs/read_write.c:684
 ksys_write+0xda/0x1a0 fs/read_write.c:736
 __do_sys_write fs/read_write.c:747 [inline]
 __se_sys_write fs/read_write.c:744 [inline]
 __x64_sys_write+0x40/0x50 fs/read_write.c:744
 x64_sys_call+0x2cdd/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:2
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd0/0x1a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

write to 0xffff8881187eea50 of 8 bytes by task 13668 on cpu 1:
 igmp_heard_query net/ipv4/igmp.c:1012 [inline]
 igmp_rcv+0x1279/0x14f0 net/ipv4/igmp.c:1103
 ip_protocol_deliver_rcu+0x420/0x780 net/ipv4/ip_input.c:205
 ip_local_deliver_finish+0x184/0x220 net/ipv4/ip_input.c:233
 NF_HOOK include/linux/netfilter.h:314 [inline]
 ip_local_deliver+0xe8/0x1c0 net/ipv4/ip_input.c:254
 dst_input include/net/dst.h:469 [inline]
 ip_rcv_finish+0x188/0x1a0 net/ipv4/ip_input.c:447
 NF_HOOK include/linux/netfilter.h:314 [inline]
 ip_rcv+0x62/0x140 net/ipv4/ip_input.c:567
 __netif_receive_skb_one_core net/core/dev.c:5887 [inline]
 __netif_receive_skb+0xff/0x270 net/core/dev.c:6000
 netif_receive_skb_internal net/core/dev.c:6086 [inline]
 netif_receive_skb+0x4b/0x2e0 net/core/dev.c:6145
 tun_rx_batched+0xfc/0x430 drivers/net/tun.c:1485
 tun_get_user+0x1e07/0x24d0 drivers/net/tun.c:1938
 tun_chr_write_iter+0x15e/0x210 drivers/net/tun.c:1984
 new_sync_write fs/read_write.c:591 [inline]
 vfs_write+0x49d/0x8d0 fs/read_write.c:684
 ksys_write+0xda/0x1a0 fs/read_write.c:736
 __do_sys_write fs/read_write.c:747 [inline]
 __se_sys_write fs/read_write.c:744 [inline]
 __x64_sys_write+0x40/0x50 fs/read_write.c:744
 x64_sys_call+0x2cdd/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:2
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd0/0x1a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000000000 -> 0x0000000000000001

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 13668 Comm: syz.0.3330 Not tainted 6.15.0-rc5-syzkaller-00022-g01f95500a162 #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025
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