==================================================================
BUG: KCSAN: data-race in memcpy_and_pad / rcu_tasks_trace_pregp_step

write to 0xffff88810b84949c 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+0x7f6/0x8e0 kernel/rcu/tasks.h:622
 rcu_tasks_kthread+0xf7/0x110 kernel/rcu/tasks.h:658
 kthread+0x489/0x510 kernel/kthread.c:464
 ret_from_fork+0xda/0x150 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffff88810b849040 of 3200 bytes by task 11591 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+0x399/0x1f90 kernel/fork.c:1999
 kernel_clone+0x16c/0x5b0 kernel/fork.c:2599
 user_mode_thread+0x7d/0xb0 kernel/fork.c:2677
 call_usermodehelper_exec_sync kernel/umh.c:132 [inline]
 call_usermodehelper_exec_work+0x7a/0x160 kernel/umh.c:163
 process_one_work kernel/workqueue.c:3238 [inline]
 process_scheduled_works+0x4cb/0x9d0 kernel/workqueue.c:3321
 worker_thread+0x582/0x770 kernel/workqueue.c:3402
 kthread+0x489/0x510 kernel/kthread.c:464
 ret_from_fork+0xda/0x150 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 11591 Comm: kworker/u8:11 Not tainted 6.16.0-rc5-syzkaller-00038-g733923397fd9 #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Workqueue: events_unbound call_usermodehelper_exec_work
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EXT4-fs error (device loop0): ext4_mb_generate_buddy:1220: group 0, block bitmap and bg descriptor inconsistent: 25 vs 4278190105 free clusters
EXT4-fs (loop0): Delayed block allocation failed for inode 15 at logical offset 0 with max blocks 1 with error 28
EXT4-fs (loop0): This should not happen!! Data will be lost

EXT4-fs (loop0): Total free blocks count 0
EXT4-fs (loop0): Free/Dirty block details
EXT4-fs (loop0): free_blocks=68451041280
EXT4-fs (loop0): dirty_blocks=16416
EXT4-fs (loop0): Block reservation details
EXT4-fs (loop0): i_reserved_data_blocks=1026