syzbot

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BUG: KCSAN: data-race in copy_fs / ksys_unshare

read-write to 0xffff88813f5aafc0 of 4 bytes by task 26897 on cpu 1:
 copy_fs+0xd1/0xf0 kernel/fork.c:1758
 copy_process+0xf93/0x2180 kernel/fork.c:2494
 kernel_clone+0x169/0x560 kernel/fork.c:2911
 __do_sys_clone kernel/fork.c:3054 [inline]
 __se_sys_clone kernel/fork.c:3038 [inline]
 __x64_sys_clone+0xe8/0x120 kernel/fork.c:3038
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

read to 0xffff88813f5aafc0 of 4 bytes by task 26924 on cpu 0:
 unshare_fs kernel/fork.c:3350 [inline]
 ksys_unshare+0x238/0x6d0 kernel/fork.c:3428
 __do_sys_unshare kernel/fork.c:3508 [inline]
 __se_sys_unshare kernel/fork.c:3506 [inline]
 __x64_sys_unshare+0x1f/0x30 kernel/fork.c:3506
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

value changed: 0x00000003 -> 0x00000004

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 26924 Comm: syz-executor.4 Tainted: G        W          6.4.0-syzkaller-11311-g24be4d0b46bb #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/27/2023
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