syzbot

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BUG: KCSAN: data-race in memcpy_and_pad / release_task

write to 0xffff88817e1a84c8 of 8 bytes by task 24530 on cpu 0:
 __list_del include/linux/list.h:203 [inline]
 __list_del_entry include/linux/list.h:226 [inline]
 list_del_rcu include/linux/rculist.h:178 [inline]
 __unhash_process kernel/exit.c:149 [inline]
 __exit_signal kernel/exit.c:212 [inline]
 release_task+0x6f9/0xb60 kernel/exit.c:267
 wait_task_zombie kernel/exit.c:1269 [inline]
 wait_consider_task+0x114a/0x1660 kernel/exit.c:1496
 do_wait_thread kernel/exit.c:1559 [inline]
 __do_wait+0xfa/0x510 kernel/exit.c:1677
 do_wait+0xb7/0x250 kernel/exit.c:1711
 kernel_wait4+0x16b/0x1e0 kernel/exit.c:1870
 __do_sys_wait4 kernel/exit.c:1898 [inline]
 __se_sys_wait4 kernel/exit.c:1894 [inline]
 __x64_sys_wait4+0x91/0x120 kernel/exit.c:1894
 x64_sys_call+0x2a6a/0x3000 arch/x86/include/generated/asm/syscalls_64.h:62
 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

read to 0xffff88817e1a8000 of 3264 bytes by task 31644 on cpu 1:
 memcpy_and_pad+0x48/0x80 lib/string_helpers.c:1007
 arch_dup_task_struct+0x2c/0x40 arch/x86/kernel/process.c:108
 dup_task_struct+0x83/0x6b0 kernel/fork.c:877
 copy_process+0x399/0x2000 kernel/fork.c:2012
 kernel_clone+0x16c/0x5c0 kernel/fork.c:2609
 __do_sys_clone3 kernel/fork.c:2911 [inline]
 __se_sys_clone3+0x1c2/0x200 kernel/fork.c:2890
 __x64_sys_clone3+0x31/0x40 kernel/fork.c:2890
 x64_sys_call+0x1fc9/0x3000 arch/x86/include/generated/asm/syscalls_64.h:436
 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: 1 UID: 0 PID: 31644 Comm: syz.3.9885 Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
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