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BUG: KCSAN: data-race in atime_needs_update / inode_update_timestamps

write to 0xffff8881155d1264 of 4 bytes by task 3629 on cpu 1:
 inode_set_mtime_to_ts include/linux/fs.h:1604 [inline]
 inode_update_timestamps+0x166/0x280 fs/inode.c:1962
 generic_update_time fs/inode.c:1997 [inline]
 inode_update_time fs/inode.c:2017 [inline]
 __file_update_time fs/inode.c:2206 [inline]
 file_update_time+0x229/0x2c0 fs/inode.c:2236
 fault_dirty_shared_page+0xde/0x340 mm/memory.c:3184
 do_shared_fault mm/memory.c:5149 [inline]
 do_fault mm/memory.c:5195 [inline]
 do_pte_missing mm/memory.c:3947 [inline]
 handle_pte_fault mm/memory.c:5521 [inline]
 __handle_mm_fault mm/memory.c:5664 [inline]
 handle_mm_fault+0x13f8/0x2a30 mm/memory.c:5832
 do_user_addr_fault arch/x86/mm/fault.c:1389 [inline]
 handle_page_fault arch/x86/mm/fault.c:1481 [inline]
 exc_page_fault+0x296/0x650 arch/x86/mm/fault.c:1539
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623
 rep_movs_alternative+0x4a/0x70 arch/x86/lib/copy_user_64.S:65
 copy_user_generic arch/x86/include/asm/uaccess_64.h:110 [inline]
 raw_copy_to_user arch/x86/include/asm/uaccess_64.h:131 [inline]
 copy_to_user_iter lib/iov_iter.c:25 [inline]
 iterate_ubuf include/linux/iov_iter.h:29 [inline]
 iterate_and_advance2 include/linux/iov_iter.h:245 [inline]
 iterate_and_advance include/linux/iov_iter.h:271 [inline]
 _copy_to_iter+0x137/0xb00 lib/iov_iter.c:185
 copy_to_iter include/linux/uio.h:196 [inline]
 get_random_bytes_user+0x112/0x260 drivers/char/random.c:464
 __do_sys_getrandom drivers/char/random.c:1406 [inline]
 __se_sys_getrandom drivers/char/random.c:1380 [inline]
 __x64_sys_getrandom+0xb5/0x190 drivers/char/random.c:1380
 x64_sys_call+0x2887/0x2d60 arch/x86/include/generated/asm/syscalls_64.h:319
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff8881155d1264 of 4 bytes by task 3634 on cpu 0:
 inode_get_mtime_nsec include/linux/fs.h:1590 [inline]
 inode_get_mtime include/linux/fs.h:1596 [inline]
 relatime_need_update fs/inode.c:1911 [inline]
 atime_needs_update+0x2aa/0x3e0 fs/inode.c:2057
 touch_atime+0x4a/0x350 fs/inode.c:2072
 file_accessed include/linux/fs.h:2486 [inline]
 shmem_file_splice_read+0x56a/0x5c0 mm/shmem.c:3211
 do_splice_read fs/splice.c:985 [inline]
 splice_direct_to_actor+0x26c/0x670 fs/splice.c:1089
 do_splice_direct_actor fs/splice.c:1207 [inline]
 do_splice_direct+0xd7/0x150 fs/splice.c:1233
 do_sendfile+0x3ab/0x950 fs/read_write.c:1295
 __do_sys_sendfile64 fs/read_write.c:1362 [inline]
 __se_sys_sendfile64 fs/read_write.c:1348 [inline]
 __x64_sys_sendfile64+0x110/0x150 fs/read_write.c:1348
 x64_sys_call+0xed5/0x2d60 arch/x86/include/generated/asm/syscalls_64.h:41
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00ee2b2d -> 0x0186c1ad

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 3634 Comm: syz.0.88 Not tainted 6.11.0-rc6-syzkaller-00019-g67784a74e258 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024
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