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BUG: KCSAN: data-race in bio_endio / blk_throtl_bio

read to 0xffff8880a428e814 of 2 bytes by interrupt on cpu 1:
 bio_remaining_done block/bio.c:1757 [inline]
 bio_endio+0x3e/0x4f0 block/bio.c:1787
 req_bio_endio block/blk-core.c:242 [inline]
 blk_update_request+0x427/0x7b0 block/blk-core.c:1462
 scsi_end_request+0x6b/0x3e0 drivers/scsi/scsi_lib.c:579
 scsi_io_completion+0x11d/0xc80 drivers/scsi/scsi_lib.c:963
 scsi_finish_command+0x280/0x380 drivers/scsi/scsi.c:228
 scsi_softirq_done+0x259/0x280 drivers/scsi/scsi_lib.c:1477
 blk_done_softirq+0x1eb/0x250 block/blk-softirq.c:37
 __do_softirq+0x115/0x33f kernel/softirq.c:292
 invoke_softirq kernel/softirq.c:373 [inline]
 irq_exit+0xbb/0xe0 kernel/softirq.c:413
 exiting_irq arch/x86/include/asm/apic.h:536 [inline]
 do_IRQ+0x81/0x130 arch/x86/kernel/irq.c:263
 ret_from_intr+0x0/0x19
 arch_local_irq_restore arch/x86/include/asm/paravirt.h:756 [inline]
 kcsan_setup_watchpoint+0x1d4/0x460 kernel/kcsan/core.c:436
 check_access kernel/kcsan/core.c:466 [inline]
 __tsan_write4 kernel/kcsan/core.c:595 [inline]
 __tsan_unaligned_write4+0xc4/0x100 kernel/kcsan/core.c:595
 __rcu_read_unlock+0x90/0x3c0 kernel/rcu/tree_plugin.h:380
 rcu_read_unlock include/linux/rcupdate.h:652 [inline]
 mem_cgroup_sk_alloc+0x112/0x150 mm/memcontrol.c:6853
 sk_alloc+0x202/0x540 net/core/sock.c:1678
 tun_chr_open+0x72/0x330 drivers/net/tun.c:3412
 misc_open+0x26a/0x2d0 drivers/char/misc.c:141
 chrdev_open+0x150/0x380 fs/char_dev.c:414
 do_dentry_open+0x301/0x970 fs/open.c:797
 vfs_open+0x62/0x80 fs/open.c:914
 do_last fs/namei.c:3408 [inline]
 path_openat+0xf73/0x36e0 fs/namei.c:3525
 do_filp_open+0x11e/0x1b0 fs/namei.c:3555
 do_sys_open+0x3b3/0x4f0 fs/open.c:1097
 __do_sys_openat fs/open.c:1124 [inline]
 __se_sys_openat fs/open.c:1118 [inline]
 __x64_sys_openat+0x62/0x80 fs/open.c:1118
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

write to 0xffff8880a428e814 of 2 bytes by task 30404 on cpu 0:
 bio_set_flag include/linux/bio.h:239 [inline]
 blk_throtl_bio+0x113/0x1830 block/blk-throttle.c:2217
 blkcg_bio_issue_check include/linux/blk-cgroup.h:745 [inline]
 generic_make_request_checks+0x6ef/0x1130 block/blk-core.c:962
 generic_make_request+0x3e/0x740 block/blk-core.c:1018
 __blk_queue_split+0x767/0xb40 block/blk-merge.c:332
 blk_mq_make_request+0x104/0xf60 block/blk-mq.c:1959
 generic_make_request block/blk-core.c:1064 [inline]
 generic_make_request+0x196/0x740 block/blk-core.c:1006
 submit_bio+0x96/0x3c0 block/blk-core.c:1190
 dio_bio_submit fs/direct-io.c:481 [inline]
 do_blockdev_direct_IO+0x64e1/0x78c0 fs/direct-io.c:1353
 __blockdev_direct_IO+0x86/0xa0 fs/direct-io.c:1412
 ext4_direct_IO_write fs/ext4/inode.c:3742 [inline]
 ext4_direct_IO+0x76c/0xfb0 fs/ext4/inode.c:3871
 generic_file_direct_write+0x14d/0x2e0 mm/filemap.c:3208
 __generic_file_write_iter+0x17e/0x380 mm/filemap.c:3391
 ext4_file_write_iter+0x1bd/0xa00 fs/ext4/file.c:268
 call_write_iter include/linux/fs.h:1895 [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+0xd5/0x1b0 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/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 30404 Comm: syz-executor.2 Not tainted 5.4.0-rc7+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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