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BUG: KCSAN: data-race in wb_timer_fn / wbt_inflight_cb

write to 0xffff8881289aab04 of 4 bytes by interrupt on cpu 0:
 calc_wb_limits block/blk-wbt.c:304 [inline]
 scale_up block/blk-wbt.c:313 [inline]
 wb_timer_fn+0x573/0xa40 block/blk-wbt.c:374
 blk_stat_timer_fn+0x3f4/0x410 block/blk-stat.c:99
 call_timer_fn+0x30/0x2a0 kernel/time/timer.c:1413
 expire_timers+0x116/0x290 kernel/time/timer.c:1458
 __run_timers+0x348/0x3e0 kernel/time/timer.c:1755
 run_timer_softirq+0x2e/0x60 kernel/time/timer.c:1768
 __do_softirq+0x198/0x360 kernel/softirq.c:298
 asm_call_on_stack+0xf/0x20 arch/x86/entry/entry_64.S:706
 __run_on_irqstack arch/x86/include/asm/irq_stack.h:22 [inline]
 run_on_irqstack_cond arch/x86/include/asm/irq_stack.h:48 [inline]
 do_softirq_own_stack+0x5d/0x80 arch/x86/kernel/irq_64.c:77
 invoke_softirq kernel/softirq.c:393 [inline]
 __irq_exit_rcu+0x115/0x120 kernel/softirq.c:423
 sysvec_apic_timer_interrupt+0xba/0xd0 arch/x86/kernel/apic/apic.c:1091
 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:581
 __tsan_read8+0x0/0x180 kernel/kcsan/core.c:604
 sctp_bind_addr_state+0x72/0x100 net/sctp/bind_addr.c:404
 sctp_copy_local_addr_list+0x166/0x220 net/sctp/protocol.c:162
 sctp_copy_one_addr+0x7d/0x3b0 net/sctp/bind_addr.c:457
 sctp_bind_addr_copy+0x8c/0x2b0 net/sctp/bind_addr.c:56
 sctp_assoc_set_bind_addr_from_ep+0xb7/0xc0 net/sctp/associola.c:1582
 sctp_sf_do_unexpected_init+0x33c/0x8e0 net/sctp/sm_statefuns.c:1543
 sctp_sf_do_5_2_1_siminit+0x38/0x50 net/sctp/sm_statefuns.c:1680
 sctp_do_sm+0x99/0x3120 net/sctp/sm_sideeffect.c:1153
 sctp_assoc_bh_rcv+0x2de/0x480 net/sctp/associola.c:1044
 sctp_inq_push+0x10f/0x120 net/sctp/inqueue.c:80
 sctp_backlog_rcv+0xf0/0x660 net/sctp/input.c:344
 sk_backlog_rcv include/net/sock.h:1011 [inline]
 __release_sock+0xf5/0x260 net/core/sock.c:2542
 release_sock+0x40/0x110 net/core/sock.c:3065
 sctp_wait_for_connect+0x1c3/0x300 net/sctp/socket.c:9065
 sctp_sendmsg_to_asoc+0x9d7/0xb60 net/sctp/socket.c:1867
 sctp_sendmsg+0x1286/0x1a90 net/sctp/socket.c:2013
 inet_sendmsg+0x5f/0x80 net/ipv4/af_inet.c:817
 sock_sendmsg_nosec net/socket.c:651 [inline]
 sock_sendmsg net/socket.c:671 [inline]
 __sys_sendto+0x2ae/0x380 net/socket.c:1992
 __do_sys_sendto net/socket.c:2004 [inline]
 __se_sys_sendto net/socket.c:2000 [inline]
 __x64_sys_sendto+0x74/0x90 net/socket.c:2000
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8881289aab04 of 4 bytes by task 15025 on cpu 1:
 rwb_enabled block/blk-wbt.c:80 [inline]
 get_limit block/blk-wbt.c:458 [inline]
 wbt_inflight_cb+0x3f/0x220 block/blk-wbt.c:495
 rq_qos_wait+0xac/0x220 block/blk-rq-qos.c:266
 __wbt_wait block/blk-wbt.c:518 [inline]
 wbt_wait+0x1bb/0x2b0 block/blk-wbt.c:583
 __rq_qos_throttle+0x39/0x70 block/blk-rq-qos.c:72
 rq_qos_throttle block/blk-rq-qos.h:182 [inline]
 blk_mq_submit_bio+0x244/0x1130 block/blk-mq.c:2168
 __submit_bio_noacct_mq block/blk-core.c:1179 [inline]
 submit_bio_noacct+0x772/0x950 block/blk-core.c:1212
 submit_bio+0x200/0x370 block/blk-core.c:1282
 ext4_io_submit+0xcd/0xf0 fs/ext4/page-io.c:382
 ext4_writepages+0x143a/0x1ef0 fs/ext4/inode.c:2801
 do_writepages+0x7b/0x150 mm/page-writeback.c:2352
 __filemap_fdatawrite_range+0x19b/0x1d0 mm/filemap.c:422
 filemap_write_and_wait_range+0x8b/0x2a0 mm/filemap.c:655
 iomap_dio_rw+0x371/0x980 fs/iomap/direct-io.c:478
 ext4_dio_read_iter fs/ext4/file.c:77 [inline]
 ext4_file_read_iter+0x3be/0x420 fs/ext4/file.c:129
 call_read_iter include/linux/fs.h:1876 [inline]
 generic_file_splice_read+0x22b/0x310 fs/splice.c:312
 do_splice_to fs/splice.c:870 [inline]
 splice_direct_to_actor+0x2a8/0x660 fs/splice.c:950
 do_splice_direct+0xf2/0x170 fs/splice.c:1059
 do_sendfile+0x56a/0xba0 fs/read_write.c:1540
 __do_sys_sendfile64 fs/read_write.c:1601 [inline]
 __se_sys_sendfile64 fs/read_write.c:1587 [inline]
 __x64_sys_sendfile64+0xf2/0x130 fs/read_write.c:1587
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 15025 Comm: syz-executor.5 Not tainted 5.9.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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