syzbot

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BUG: KCSAN: data-race in shmem_fallocate / shmem_writeout

read-write to 0xffffc9000281fe28 of 8 bytes by task 21123 on cpu 0:
 shmem_writeout+0x2f1/0x920 mm/shmem.c:1667
 writeout mm/vmscan.c:648 [inline]
 pageout mm/vmscan.c:697 [inline]
 shrink_folio_list+0x1e89/0x2730 mm/vmscan.c:1416
 evict_folios+0x2a60/0x35c0 mm/vmscan.c:4708
 try_to_shrink_lruvec+0x606/0x980 mm/vmscan.c:4871
 lru_gen_shrink_lruvec mm/vmscan.c:5020 [inline]
 shrink_lruvec+0x24e/0x1b60 mm/vmscan.c:5774
 shrink_node_memcgs mm/vmscan.c:6010 [inline]
 shrink_node+0x67e/0x20c0 mm/vmscan.c:6051
 shrink_zones mm/vmscan.c:6290 [inline]
 do_try_to_free_pages+0x408/0xc80 mm/vmscan.c:6352
 try_to_free_mem_cgroup_pages+0x1f5/0x470 mm/vmscan.c:6673
 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:5266
 alloc_pages_mpol+0xb3/0x260 mm/mempolicy.c:2485
 alloc_frozen_pages_noprof mm/mempolicy.c:2556 [inline]
 alloc_pages_noprof+0x8f/0x130 mm/mempolicy.c:2576
 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:6696
 ip_set_alloc+0x24/0x30 net/netfilter/ipset/ip_set_core.c:261
 hash_netiface_create+0x282/0x740 net/netfilter/ipset/ip_set_hash_gen.h:1568
 ip_set_create+0x3cf/0x970 net/netfilter/ipset/ip_set_core.c:1109
 nfnetlink_rcv_msg+0x509/0x5d0 net/netfilter/nfnetlink.c:302
 netlink_rcv_skb+0x123/0x220 net/netlink/af_netlink.c:2550
 nfnetlink_rcv+0x167/0x1720 net/netfilter/nfnetlink.c:669
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x5c0/0x690 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x5c8/0x6f0 net/netlink/af_netlink.c:1894
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg net/socket.c:742 [inline]
 ____sys_sendmsg+0x5af/0x600 net/socket.c:2592
 ___sys_sendmsg+0x195/0x1e0 net/socket.c:2646
 __sys_sendmsg net/socket.c:2678 [inline]
 __do_sys_sendmsg net/socket.c:2683 [inline]
 __se_sys_sendmsg net/socket.c:2681 [inline]
 __x64_sys_sendmsg+0xd4/0x160 net/socket.c:2681
 x64_sys_call+0x194c/0x3020 arch/x86/include/generated/asm/syscalls_64.h:47
 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 0xffffc9000281fe28 of 8 bytes by task 21149 on cpu 1:
 shmem_fallocate+0x5c0/0x920 mm/shmem.c:3786
 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: 0x000000000000010d -> 0x000000000000011a

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 21149 Comm: syz.5.3338 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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