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BUG: KCSAN: data-race in _extract_crng / crng_reseed

write to 0xffffffff841ab058 of 8 bytes by task 1817 on cpu 1:
 crng_reseed+0x404/0x6a0 drivers/char/random.c:965
 _extract_crng+0xcc/0x2d0 drivers/char/random.c:996
 crng_reseed+0x69/0x6a0 drivers/char/random.c:952
 _extract_crng+0xcc/0x2d0 drivers/char/random.c:996
 extract_crng drivers/char/random.c:1016 [inline]
 get_random_u64+0xf8/0x1f0 drivers/char/random.c:2178
 get_random_long include/linux/random.h:61 [inline]
 get_random_canary include/linux/random.h:83 [inline]
 dup_task_struct+0x3db/0x630 kernel/fork.c:923
 copy_process+0x3ff/0x2f70 kernel/fork.c:1952
 kernel_clone+0x14b/0x680 kernel/fork.c:2509
 __do_sys_clone kernel/fork.c:2626 [inline]
 __se_sys_clone kernel/fork.c:2610 [inline]
 __x64_sys_clone+0xb4/0xe0 kernel/fork.c:2610
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffffffff841ab058 of 8 bytes by task 1818 on cpu 0:
 _extract_crng+0x47/0x2d0 drivers/char/random.c:994
 crng_reseed+0x69/0x6a0 drivers/char/random.c:952
 _extract_crng+0xcc/0x2d0 drivers/char/random.c:996
 extract_crng drivers/char/random.c:1016 [inline]
 get_random_u64+0xf8/0x1f0 drivers/char/random.c:2178
 get_random_long include/linux/random.h:61 [inline]
 get_random_canary include/linux/random.h:83 [inline]
 dup_task_struct+0x3db/0x630 kernel/fork.c:923
 copy_process+0x3ff/0x2f70 kernel/fork.c:1952
 kernel_clone+0x14b/0x680 kernel/fork.c:2509
 __do_sys_clone kernel/fork.c:2626 [inline]
 __se_sys_clone kernel/fork.c:2610 [inline]
 __x64_sys_clone+0xb4/0xe0 kernel/fork.c:2610
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x0000000100000074 -> 0x0000000100007656

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 1818 Comm: syz-executor.3 Not tainted 5.14.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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