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BUG: KCSAN: data-race in enqueue_timer / mod_timer

read to 0xffff888126382d30 of 8 bytes by task 7862 on cpu 0:
 __mod_timer kernel/time/timer.c:963 [inline]
 mod_timer+0x59/0x7a0 kernel/time/timer.c:1100
 sk_reset_timer+0x2d/0xd0 net/core/sock.c:2840
 inet_csk_reset_xmit_timer include/net/inet_connection_sock.h:234 [inline]
 tcp_reset_xmit_timer include/net/tcp.h:1296 [inline]
 tcp_rearm_rto net/ipv4/tcp_input.c:3011 [inline]
 tcp_rearm_rto+0x1e7/0x2a0 net/ipv4/tcp_input.c:2987
 tcp_event_new_data_sent+0x218/0x220 net/ipv4/tcp_output.c:77
 tcp_write_xmit+0xa97/0x3190 net/ipv4/tcp_output.c:2448
 __tcp_push_pending_frames+0x7b/0x1d0 net/ipv4/tcp_output.c:2617
 tcp_push+0x1f7/0x3e0 net/ipv4/tcp.c:726
 tcp_sendmsg_locked+0x1d71/0x2040 net/ipv4/tcp.c:1405
 tcp_sendmsg+0x39/0x60 net/ipv4/tcp.c:1436
 inet_sendmsg+0x6d/0x90 net/ipv4/af_inet.c:807
 sock_sendmsg_nosec net/socket.c:639 [inline]
 sock_sendmsg+0x9f/0xc0 net/socket.c:659
 sock_write_iter+0x16b/0x210 net/socket.c:991
 call_write_iter include/linux/fs.h:1902 [inline]
 new_sync_write+0x388/0x4a0 fs/read_write.c:483
 __vfs_write+0xb1/0xc0 fs/read_write.c:496
 vfs_write fs/read_write.c:558 [inline]
 vfs_write+0x18a/0x390 fs/read_write.c:542
 ksys_write+0x17b/0x1b0 fs/read_write.c:611
 __do_sys_write fs/read_write.c:623 [inline]
 __se_sys_write fs/read_write.c:620 [inline]
 __x64_sys_write+0x4c/0x60 fs/read_write.c:620
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

write to 0xffff888126382d30 of 8 bytes by task 7845 on cpu 1:
 hlist_add_head include/linux/list.h:787 [inline]
 enqueue_timer+0x6c/0x210 kernel/time/timer.c:540
 __mod_timer kernel/time/timer.c:1050 [inline]
 mod_timer+0x4b3/0x7a0 kernel/time/timer.c:1100
 sk_reset_timer+0x2d/0xd0 net/core/sock.c:2840
 inet_csk_reset_xmit_timer include/net/inet_connection_sock.h:234 [inline]
 tcp_reset_xmit_timer include/net/tcp.h:1296 [inline]
 tcp_rearm_rto net/ipv4/tcp_input.c:3011 [inline]
 tcp_rearm_rto+0x1e7/0x2a0 net/ipv4/tcp_input.c:2987
 tcp_event_new_data_sent+0x218/0x220 net/ipv4/tcp_output.c:77
 tcp_write_xmit+0xa97/0x3190 net/ipv4/tcp_output.c:2448
 __tcp_push_pending_frames+0x7b/0x1d0 net/ipv4/tcp_output.c:2617
 tcp_push+0x1f7/0x3e0 net/ipv4/tcp.c:726
 tcp_sendmsg_locked+0x1d71/0x2040 net/ipv4/tcp.c:1405
 tcp_sendmsg+0x39/0x60 net/ipv4/tcp.c:1436
 inet_sendmsg+0x6d/0x90 net/ipv4/af_inet.c:807
 sock_sendmsg_nosec net/socket.c:639 [inline]
 sock_sendmsg+0x9f/0xc0 net/socket.c:659
 sock_write_iter+0x16b/0x210 net/socket.c:991
 call_write_iter include/linux/fs.h:1902 [inline]
 new_sync_write+0x388/0x4a0 fs/read_write.c:483
 __vfs_write+0xb1/0xc0 fs/read_write.c:496
 vfs_write fs/read_write.c:558 [inline]
 vfs_write+0x18a/0x390 fs/read_write.c:542
 ksys_write+0x17b/0x1b0 fs/read_write.c:611
 __do_sys_write fs/read_write.c:623 [inline]
 __se_sys_write fs/read_write.c:620 [inline]
 __x64_sys_write+0x4c/0x60 fs/read_write.c:620
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 7845 Comm: sshd Not tainted 5.5.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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