syzbot

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BUG: KCSAN: data-race in css_set_move_task / memcpy_and_pad

write to 0xffff888104a9bac8 of 8 bytes by task 10991 on cpu 0:
 __list_del include/linux/list.h:203 [inline]
 __list_del_entry include/linux/list.h:226 [inline]
 list_del_init include/linux/list.h:295 [inline]
 css_set_move_task+0x212/0x430 kernel/cgroup/cgroup.c:932
 do_cgroup_task_dead kernel/cgroup/cgroup.c:6998 [inline]
 cgroup_task_dead+0x6f/0x2b0 kernel/cgroup/cgroup.c:7062
 finish_task_switch+0x1b5/0x280 kernel/sched/core.c:5190
 context_switch kernel/sched/core.c:5298 [inline]
 __schedule+0x85a/0xd40 kernel/sched/core.c:6907
 preempt_schedule_common+0x11/0x30 kernel/sched/core.c:7091
 preempt_schedule_thunk+0x16/0x30 arch/x86/entry/thunk.S:12
 __up_read kernel/locking/rwsem.c:1365 [inline]
 up_read+0x62/0x70 kernel/locking/rwsem.c:1633
 i_mmap_unlock_read include/linux/fs.h:537 [inline]
 __rmap_walk_file+0x290/0x2b0 mm/rmap.c:3017
 try_to_unmap+0x1e3/0x210 mm/rmap.c:-1
 shrink_folio_list+0x11f7/0x2730 mm/vmscan.c:1366
 reclaim_folio_list+0x9f/0x220 mm/vmscan.c:2196
 reclaim_pages+0x21e/0x280 mm/vmscan.c:2233
 madvise_cold_or_pageout_pte_range+0xd6a/0xdc0 mm/madvise.c:561
 walk_pmd_range mm/pagewalk.c:130 [inline]
 walk_pud_range mm/pagewalk.c:224 [inline]
 walk_p4d_range mm/pagewalk.c:262 [inline]
 walk_pgd_range+0xa4a/0x14d0 mm/pagewalk.c:303
 __walk_page_range+0xdd/0x340 mm/pagewalk.c:411
 walk_page_range_vma_unsafe+0x2cd/0x320 mm/pagewalk.c:715
 walk_page_range_vma+0x56/0x70 mm/pagewalk.c:725
 madvise_vma_behavior+0x1d11/0x20c0 mm/madvise.c:-1
 madvise_walk_vmas mm/madvise.c:1719 [inline]
 madvise_do_behavior+0x5de/0xa10 mm/madvise.c:1935
 do_madvise+0x10e/0x190 mm/madvise.c:2028
 __do_sys_madvise mm/madvise.c:2037 [inline]
 __se_sys_madvise mm/madvise.c:2035 [inline]
 __x64_sys_madvise+0x63/0x80 mm/madvise.c:2035
 x64_sys_call+0x1eff/0x3020 arch/x86/include/generated/asm/syscalls_64.h:29
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888104a9b180 of 3264 bytes by task 11192 on cpu 1:
 memcpy_and_pad+0x48/0x80 lib/string_helpers.c:1008
 arch_dup_task_struct+0x2c/0x40 arch/x86/kernel/process.c:108
 dup_task_struct+0x6e/0x940 kernel/fork.c:920
 copy_process+0x37e/0x20c0 kernel/fork.c:2050
 kernel_clone+0x16b/0x5d0 kernel/fork.c:2654
 __do_sys_clone kernel/fork.c:2795 [inline]
 __se_sys_clone kernel/fork.c:2779 [inline]
 __x64_sys_clone+0x143/0x180 kernel/fork.c:2779
 x64_sys_call+0x1222/0x3020 arch/x86/include/generated/asm/syscalls_64.h:57
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x370 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: 11192 Comm: dhcpcd-run-hook Tainted: G        W           syzkaller #0 PREEMPT(full) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
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