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BUG: KCSAN: data-race in complete_signal / start_this_handle

write to 0xffff88812cf6c02c of 4 bytes by task 9910 on cpu 1:
 memalloc_nofs_save include/linux/sched/mm.h:244 [inline]
 start_this_handle+0xf4c/0x1010 fs/jbd2/transaction.c:452
 jbd2__journal_start+0x1fc/0x3f0 fs/jbd2/transaction.c:503
 __ext4_journal_start_sb+0x159/0x310 fs/ext4/ext4_jbd2.c:105
 __ext4_journal_start fs/ext4/ext4_jbd2.h:320 [inline]
 ext4_dirty_inode+0x78/0xc0 fs/ext4/inode.c:5951
 __mark_inode_dirty+0x72/0x6b0 fs/fs-writeback.c:2262
 generic_update_time fs/inode.c:1763 [inline]
 update_time fs/inode.c:1776 [inline]
 file_update_time+0x3ac/0x3f0 fs/inode.c:1991
 ext4_page_mkwrite+0x146/0xf50 fs/ext4/inode.c:6075
 do_page_mkwrite mm/memory.c:2726 [inline]
 do_shared_fault+0x218/0x680 mm/memory.c:4005
 do_fault mm/memory.c:4073 [inline]
 handle_pte_fault mm/memory.c:4320 [inline]
 __handle_mm_fault mm/memory.c:4455 [inline]
 handle_mm_fault+0x12f0/0x18a0 mm/memory.c:4553
 do_user_addr_fault+0x60c/0xc00 arch/x86/mm/fault.c:1384
 handle_page_fault arch/x86/mm/fault.c:1469 [inline]
 exc_page_fault+0x94/0x2a0 arch/x86/mm/fault.c:1525
 asm_exc_page_fault+0x1e/0x30 arch/x86/include/asm/idtentry.h:580

read to 0xffff88812cf6c02c of 4 bytes by interrupt on cpu 0:
 wants_signal kernel/signal.c:978 [inline]
 complete_signal+0x7c/0x600 kernel/signal.c:1001
 send_sigqueue+0x268/0x430 kernel/signal.c:1881
 posix_timer_event kernel/time/posix-timers.c:354 [inline]
 posix_timer_fn+0xe8/0x210 kernel/time/posix-timers.c:380
 __run_hrtimer+0x163/0x460 kernel/time/hrtimer.c:1519
 __hrtimer_run_queues kernel/time/hrtimer.c:1583 [inline]
 hrtimer_interrupt+0x36e/0xa30 kernel/time/hrtimer.c:1645
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1089 [inline]
 __sysvec_apic_timer_interrupt+0x6f/0x200 arch/x86/kernel/apic/apic.c:1106
 asm_call_irq_on_stack+0xf/0x20
 __run_sysvec_on_irqstack arch/x86/include/asm/irq_stack.h:37 [inline]
 run_sysvec_on_irqstack_cond arch/x86/include/asm/irq_stack.h:89 [inline]
 sysvec_apic_timer_interrupt+0x52/0x90 arch/x86/kernel/apic/apic.c:1100
 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:635
 check_kcov_mode kernel/kcov.c:165 [inline]
 write_comp_data kernel/kcov.c:218 [inline]
 __sanitizer_cov_trace_const_cmp4+0x31/0xa0 kernel/kcov.c:284
 ext4_chksum fs/ext4/ext4.h:2322 [inline]
 ext4_group_desc_csum+0x1c3/0x4b0 fs/ext4/super.c:2796
 ext4_group_desc_csum_set+0xa8/0x140 fs/ext4/super.c:2842
 ext4_mb_mark_diskspace_used+0x779/0xc50 fs/ext4/mballoc.c:3249
 ext4_mb_new_blocks+0xa3d/0x1150 fs/ext4/mballoc.c:4993
 ext4_ext_map_blocks+0x146f/0x1fd0 fs/ext4/extents.c:4238
 ext4_map_blocks+0x726/0xff0 fs/ext4/inode.c:637
 mpage_map_one_extent+0x10d/0x3a0 fs/ext4/inode.c:2396
 mpage_map_and_submit_extent fs/ext4/inode.c:2449 [inline]
 ext4_writepages+0xa51/0x1e70 fs/ext4/inode.c:2801
 do_writepages+0x7b/0x150 mm/page-writeback.c:2352
 __filemap_fdatawrite_range+0x19d/0x1d0 mm/filemap.c:424
 file_write_and_wait_range+0x9f/0x120 mm/filemap.c:763
 ext4_sync_file+0x105/0x6e0 fs/ext4/fsync.c:151
 vfs_fsync_range+0x107/0x120 fs/sync.c:200
 generic_write_sync include/linux/fs.h:2737 [inline]
 ext4_buffered_write_iter+0x38f/0x3e0 fs/ext4/file.c:277
 ext4_file_write_iter+0x48a/0x10b0 fs/ext4/file.c:502
 call_write_iter include/linux/fs.h:1901 [inline]
 do_iter_readv_writev+0x2cb/0x360 fs/read_write.c:740
 do_iter_write+0x112/0x4c0 fs/read_write.c:866
 vfs_iter_write+0x4c/0x70 fs/read_write.c:907
 iter_file_splice_write+0x40a/0x750 fs/splice.c:689
 do_splice_from fs/splice.c:767 [inline]
 direct_splice_actor+0x80/0xa0 fs/splice.c:936
 splice_direct_to_actor+0x345/0x650 fs/splice.c:891
 do_splice_direct+0xf5/0x170 fs/splice.c:979
 do_sendfile+0x7a6/0xe20 fs/read_write.c:1260
 __do_sys_sendfile64 fs/read_write.c:1319 [inline]
 __se_sys_sendfile64 fs/read_write.c:1311 [inline]
 __x64_sys_sendfile64+0xa9/0x130 fs/read_write.c:1311
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 9899 Comm: syz-executor.0 Not tainted 5.11.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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