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BUG: KCSAN: data-race in shmem_fallocate / shmem_writeout

read-write to 0xffffc90001dabe28 of 8 bytes by task 10462 on cpu 0:
 shmem_writeout+0x2f1/0x920 mm/shmem.c:1667
 writeout mm/vmscan.c:650 [inline]
 pageout mm/vmscan.c:699 [inline]
 shrink_folio_list+0x1f1f/0x2820 mm/vmscan.c:1425
 evict_folios+0x2a60/0x35c0 mm/vmscan.c:4718
 try_to_shrink_lruvec+0x81b/0xbf0 mm/vmscan.c:4881
 lru_gen_shrink_lruvec mm/vmscan.c:5030 [inline]
 shrink_lruvec+0x255/0x1c60 mm/vmscan.c:5784
 shrink_node_memcgs mm/vmscan.c:6020 [inline]
 shrink_node+0x67a/0x2130 mm/vmscan.c:6061
 shrink_zones mm/vmscan.c:6300 [inline]
 do_try_to_free_pages+0x408/0xc80 mm/vmscan.c:6362
 try_to_free_mem_cgroup_pages+0x1f5/0x470 mm/vmscan.c:6683
 try_charge_memcg+0x37e/0xa10 mm/memcontrol.c:2414
 obj_cgroup_charge_pages+0x23/0xc0 mm/memcontrol.c:2857
 __memcg_kmem_charge_page+0x9e/0x170 mm/memcontrol.c:2901
 __alloc_frozen_pages_noprof+0x18a/0x360 mm/page_alloc.c:5267
 alloc_pages_mpol+0xb3/0x260 mm/mempolicy.c:2490
 alloc_frozen_pages_noprof mm/mempolicy.c:2561 [inline]
 alloc_pages_noprof+0x8f/0x140 mm/mempolicy.c:2581
 vm_area_alloc_pages mm/vmalloc.c:3731 [inline]
 __vmalloc_area_node mm/vmalloc.c:3876 [inline]
 __vmalloc_node_range_noprof+0xa46/0x12b0 mm/vmalloc.c:4064
 __kvmalloc_node_noprof+0x3d4/0x650 mm/slub.c:6780
 futex_hash_allocate+0x190/0x9d0 kernel/futex/core.c:1812
 futex_hash_prctl+0xd8/0xf0 kernel/futex/core.c:1958
 __do_sys_prctl kernel/sys.c:2884 [inline]
 __se_sys_prctl+0xa3d/0x13f0 kernel/sys.c:2533
 __x64_sys_prctl+0x67/0x80 kernel/sys.c:2533
 x64_sys_call+0x2533/0x3020 arch/x86/include/generated/asm/syscalls_64.h:158
 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 0xffffc90001dabe28 of 8 bytes by task 10459 on cpu 1:
 shmem_fallocate+0x5c0/0x920 mm/shmem.c:3787
 vfs_fallocate+0x3b6/0x450 fs/open.c:340
 ksys_fallocate fs/open.c:364 [inline]
 __do_sys_fallocate fs/open.c:369 [inline]
 __se_sys_fallocate fs/open.c:367 [inline]
 __x64_sys_fallocate+0x7a/0xd0 fs/open.c:367
 x64_sys_call+0x298e/0x3020 arch/x86/include/generated/asm/syscalls_64.h:286
 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

value changed: 0x00000000000010f7 -> 0x0000000000001100

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 10459 Comm: syz.4.2052 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
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