loop4: detected capacity change from 0 to 512
FAT-fs (loop4): Volume was not properly unmounted. Some data may be corrupt. Please run fsck.
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BUG: KCSAN: data-race in copy_folio_from_iter_atomic / copy_folio_from_iter_atomic

read to 0xffff88812f3b4000 of 4096 bytes by task 60 on cpu 1:
 memcpy_from_iter lib/iov_iter.c:73 [inline]
 iterate_bvec include/linux/iov_iter.h:123 [inline]
 iterate_and_advance2 include/linux/iov_iter.h:306 [inline]
 iterate_and_advance include/linux/iov_iter.h:330 [inline]
 __copy_from_iter lib/iov_iter.c:249 [inline]
 copy_folio_from_iter_atomic+0x7fc/0x11b0 lib/iov_iter.c:479
 generic_perform_write+0x2c2/0x490 mm/filemap.c:4272
 shmem_file_write_iter+0xc5/0xf0 mm/shmem.c:3466
 lo_rw_aio+0x6a0/0x760 drivers/block/loop.c:-1
 do_req_filebacked drivers/block/loop.c:-1 [inline]
 loop_handle_cmd drivers/block/loop.c:1923 [inline]
 loop_process_work+0x52d/0xa60 drivers/block/loop.c:1958
 loop_workfn+0x31/0x40 drivers/block/loop.c:1982
 process_one_work kernel/workqueue.c:3263 [inline]
 process_scheduled_works+0x4ce/0x9d0 kernel/workqueue.c:3346
 worker_thread+0x582/0x770 kernel/workqueue.c:3427
 kthread+0x489/0x510 kernel/kthread.c:463
 ret_from_fork+0x122/0x1b0 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

write to 0xffff88812f3b4e40 of 448 bytes by task 7132 on cpu 0:
 instrument_copy_from_user_before include/linux/instrumented.h:130 [inline]
 copy_from_user_iter lib/iov_iter.c:54 [inline]
 iterate_ubuf include/linux/iov_iter.h:30 [inline]
 iterate_and_advance2 include/linux/iov_iter.h:302 [inline]
 iterate_and_advance include/linux/iov_iter.h:330 [inline]
 __copy_from_iter lib/iov_iter.c:249 [inline]
 copy_folio_from_iter_atomic+0x2d1/0x11b0 lib/iov_iter.c:479
 generic_perform_write+0x2c2/0x490 mm/filemap.c:4272
 __generic_file_write_iter+0xec/0x120 mm/filemap.c:4368
 generic_file_write_iter+0x8d/0x2f0 mm/filemap.c:4397
 new_sync_write fs/read_write.c:593 [inline]
 vfs_write+0x52a/0x960 fs/read_write.c:686
 ksys_write+0xda/0x1a0 fs/read_write.c:738
 __do_sys_write fs/read_write.c:749 [inline]
 __se_sys_write fs/read_write.c:746 [inline]
 __x64_sys_write+0x40/0x50 fs/read_write.c:746
 x64_sys_call+0x2802/0x3000 arch/x86/include/generated/asm/syscalls_64.h:2
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 7132 Comm: syz.4.1589 Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
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