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BUG: KCSAN: data-race in igmp6_mcf_seq_show / ip6_mc_del1_src

write to 0xffff88810abff498 of 8 bytes by task 18103 on cpu 1:
 ip6_mc_del1_src+0xe9/0x270 net/ipv6/mcast.c:2288
 ip6_mc_del_src+0x278/0x430 net/ipv6/mcast.c:2342
 ip6_mc_msfilter+0x5b8/0x670 net/ipv6/mcast.c:564
 ipv6_set_mcast_msfilter+0x213/0x250 net/ipv6/ipv6_sockglue.c:229
 do_ipv6_setsockopt+0x1138/0x2250 net/ipv6/ipv6_sockglue.c:944
 ipv6_setsockopt+0x57/0x130 net/ipv6/ipv6_sockglue.c:993
 tcp_setsockopt+0x93/0xb0 net/ipv4/tcp.c:4030
 sock_common_setsockopt+0x64/0x80 net/core/sock.c:3814
 do_sock_setsockopt net/socket.c:2313 [inline]
 __sys_setsockopt+0x187/0x200 net/socket.c:2338
 __do_sys_setsockopt net/socket.c:2344 [inline]
 __se_sys_setsockopt net/socket.c:2341 [inline]
 __x64_sys_setsockopt+0x66/0x80 net/socket.c:2341
 x64_sys_call+0x282e/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:55
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88810abff498 of 8 bytes by task 18104 on cpu 0:
 igmp6_mcf_seq_show+0x92/0xf0 net/ipv6/mcast.c:3078
 traverse+0x155/0x3c0 fs/seq_file.c:111
 seq_read_iter+0x854/0x930 fs/seq_file.c:195
 seq_read+0x1ed/0x230 fs/seq_file.c:162
 pde_read fs/proc/inode.c:308 [inline]
 proc_reg_read+0x13f/0x1d0 fs/proc/inode.c:320
 do_loop_readv_writev fs/read_write.c:840 [inline]
 vfs_readv+0x3e2/0x660 fs/read_write.c:1013
 do_preadv fs/read_write.c:1125 [inline]
 __do_sys_preadv fs/read_write.c:1172 [inline]
 __se_sys_preadv fs/read_write.c:1167 [inline]
 __x64_sys_preadv+0xf4/0x1c0 fs/read_write.c:1167
 x64_sys_call+0x2680/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:296
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000000004 -> 0x0000000000000003

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 18104 Comm: syz.3.5565 Not tainted 6.13.0-rc1-syzkaller-00025-gfeffde684ac2 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
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