syzbot

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BUG: KCSAN: data-race in memcpy_and_pad / rcu_tasks_trace_pregp_step

write to 0xffff888127b2e5dc of 4 bytes by task 28 on cpu 1:
 rcu_tasks_trace_pertask_prep kernel/rcu/tasks.h:1784 [inline]
 rcu_tasks_trace_pregp_step+0x1ac/0x920 kernel/rcu/tasks.h:1828
 rcu_tasks_wait_gp+0x88/0x530 kernel/rcu/tasks.h:826
 rcu_tasks_one_gp+0x7f3/0x8e0 kernel/rcu/tasks.h:622
 rcu_tasks_kthread+0xf7/0x110 kernel/rcu/tasks.h:658
 kthread+0x486/0x510 kernel/kthread.c:464
 ret_from_fork+0xdd/0x150 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffff888127b2e180 of 3200 bytes by task 13381 on cpu 0:
 memcpy_and_pad+0x48/0x80 lib/string_helpers.c:1007
 arch_dup_task_struct+0x2c/0x40 arch/x86/kernel/process.c:98
 dup_task_struct+0x83/0x6a0 kernel/fork.c:873
 copy_process+0x399/0x1fe0 kernel/fork.c:1999
 kernel_clone+0x16c/0x5b0 kernel/fork.c:2599
 __do_sys_clone3 kernel/fork.c:2903 [inline]
 __se_sys_clone3+0x1c2/0x200 kernel/fork.c:2882
 __x64_sys_clone3+0x31/0x40 kernel/fork.c:2882
 x64_sys_call+0x10c9/0x2fb0 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: 0 UID: 0 PID: 13381 Comm: syz.2.2853 Not tainted 6.16.0-rc2-syzkaller-00231-g75f5f23f8787 #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
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