syzbot

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BUG: KCSAN: data-race in sock_enable_timestamp / udpv6_recvmsg

read to 0xffff8880a2c4dae0 of 8 bytes by task 8759 on cpu 1:
 sock_recv_ts_and_drops include/net/sock.h:2402 [inline]
 udpv6_recvmsg+0x4ff/0xeb0 net/ipv6/udp.c:337
 inet6_recvmsg+0xbb/0x240 net/ipv6/af_inet6.c:592
 sock_recvmsg_nosec+0x5c/0x70 net/socket.c:871
 ___sys_recvmsg+0x1a0/0x3e0 net/socket.c:2480
 do_recvmmsg+0x19a/0x5c0 net/socket.c:2601
 __sys_recvmmsg+0x1ef/0x200 net/socket.c:2680
 __do_sys_recvmmsg net/socket.c:2703 [inline]
 __se_sys_recvmmsg net/socket.c:2696 [inline]
 __x64_sys_recvmmsg+0x89/0xb0 net/socket.c:2696
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

write to 0xffff8880a2c4dae0 of 8 bytes by task 8770 on cpu 0:
 __set_bit include/asm-generic/bitops-instrumented.h:46 [inline]
 sock_set_flag include/net/sock.h:828 [inline]
 sock_enable_timestamp+0x7b/0xe0 net/core/sock.c:3050
 sock_gettstamp+0x5c/0x1f0 net/core/sock.c:3012
 sock_ioctl+0x28e/0x5e0 net/socket.c:1184
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:509 [inline]
 do_vfs_ioctl+0x991/0xc60 fs/ioctl.c:696
 ksys_ioctl+0xbd/0xe0 fs/ioctl.c:713
 __do_sys_ioctl fs/ioctl.c:720 [inline]
 __se_sys_ioctl fs/ioctl.c:718 [inline]
 __x64_sys_ioctl+0x4c/0x60 fs/ioctl.c:718
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 8770 Comm: syz-executor.5 Not tainted 5.4.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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