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BUG: KCSAN: data-race in _copy_to_iter / copy_folio_from_iter_atomic

write to 0xffff8881029211ff of 2 bytes by task 4903 on cpu 0:
 instrument_copy_from_user_before include/linux/instrumented.h:147 [inline]
 copy_from_user_iter lib/iov_iter.c:66 [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:261 [inline]
 copy_folio_from_iter_atomic+0x282/0x10a0 lib/iov_iter.c:491
 iomap_write_iter fs/iomap/buffered-io.c:1241 [inline]
 iomap_file_buffered_write+0x41e/0x940 fs/iomap/buffered-io.c:1309
 blkdev_buffered_write block/fops.c:710 [inline]
 blkdev_write_iter+0x391/0x490 block/fops.c:776
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x57d/0x990 fs/read_write.c:687
 ksys_pwrite64 fs/read_write.c:794 [inline]
 __do_sys_pwrite64 fs/read_write.c:802 [inline]
 __se_sys_pwrite64 fs/read_write.c:799 [inline]
 __x64_sys_pwrite64+0xfd/0x150 fs/read_write.c:799
 x64_sys_call+0xa2a/0x3020 arch/x86/include/generated/asm/syscalls_64.h:19
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888102921000 of 512 bytes by task 3290 on cpu 1:
 instrument_copy_to_user include/linux/instrumented.h:130 [inline]
 copy_to_user_iter lib/iov_iter.c:24 [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_to_iter+0x130/0xea0 lib/iov_iter.c:197
 copy_page_to_iter+0x174/0x210 lib/iov_iter.c:374
 copy_folio_to_iter include/linux/uio.h:204 [inline]
 filemap_read+0x3ed/0xa20 mm/filemap.c:2865
 blkdev_read_iter+0x21e/0x2d0 block/fops.c:830
 new_sync_read fs/read_write.c:493 [inline]
 vfs_read+0x699/0x7c0 fs/read_write.c:574
 ksys_read+0xdc/0x1a0 fs/read_write.c:716
 __do_sys_read fs/read_write.c:725 [inline]
 __se_sys_read fs/read_write.c:723 [inline]
 __x64_sys_read+0x40/0x50 fs/read_write.c:723
 x64_sys_call+0x2886/0x3020 arch/x86/include/generated/asm/syscalls_64.h:1
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3290 Comm: udevd Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
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