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BUG: KASAN: use-after-free in instrument_atomic_read_write include/linux/instrumented.h:102 [inline]
BUG: KASAN: use-after-free in atomic_fetch_add_relaxed include/linux/atomic/atomic-instrumented.h:116 [inline]
BUG: KASAN: use-after-free in __refcount_add include/linux/refcount.h:193 [inline]
BUG: KASAN: use-after-free in __refcount_inc include/linux/refcount.h:250 [inline]
BUG: KASAN: use-after-free in refcount_inc include/linux/refcount.h:267 [inline]
BUG: KASAN: use-after-free in kref_get include/linux/kref.h:45 [inline]
BUG: KASAN: use-after-free in svc_get include/linux/sunrpc/svc.h:108 [inline]
BUG: KASAN: use-after-free in nfsd_create_serv+0x11b/0x700 fs/nfsd/nfssvc.c:661
Write of size 4 at addr ffff88807b59b850 by task syz.4.100/4627

CPU: 1 PID: 4627 Comm: syz.4.100 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x188/0x24e lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:316 [inline]
 print_report+0xa8/0x210 mm/kasan/report.c:420
 kasan_report+0x10b/0x140 mm/kasan/report.c:524
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x235/0x290 mm/kasan/generic.c:189
 instrument_atomic_read_write include/linux/instrumented.h:102 [inline]
 atomic_fetch_add_relaxed include/linux/atomic/atomic-instrumented.h:116 [inline]
 __refcount_add include/linux/refcount.h:193 [inline]
 __refcount_inc include/linux/refcount.h:250 [inline]
 refcount_inc include/linux/refcount.h:267 [inline]
 kref_get include/linux/kref.h:45 [inline]
 svc_get include/linux/sunrpc/svc.h:108 [inline]
 nfsd_create_serv+0x11b/0x700 fs/nfsd/nfssvc.c:661
 nfsd_svc+0x17f/0xab0 fs/nfsd/nfssvc.c:796
 write_threads+0x2ea/0x350 fs/nfsd/nfsctl.c:424
 nfsctl_transaction_write+0x105/0x150 fs/nfsd/nfsctl.c:114
 vfs_write+0x2dc/0x9a0 fs/read_write.c:582
 ksys_write+0x14d/0x260 fs/read_write.c:637
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f404199e159
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f40428ca028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f4041c26090 RCX: 00007f404199e159
RDX: 0000000000000002 RSI: 0000200000000140 RDI: 0000000000000005
RBP: 00007f4041a3506b R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f4041c26128 R14: 00007f4041c26090 R15: 00007fff345ef2e8
 </TASK>

Allocated by task 4623:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:53
 ____kasan_kmalloc mm/kasan/common.c:375 [inline]
 __kasan_kmalloc+0x8e/0xa0 mm/kasan/common.c:384
 kmalloc include/linux/slab.h:563 [inline]
 kzalloc include/linux/slab.h:699 [inline]
 __svc_create+0x60/0x9d0 net/sunrpc/svc.c:491
 svc_create_pooled+0x71f/0x8c0 net/sunrpc/svc.c:579
 nfsd_create_serv+0x2f9/0x700 fs/nfsd/nfssvc.c:667
 __write_ports_addfd fs/nfsd/nfsctl.c:716 [inline]
 __write_ports fs/nfsd/nfsctl.c:791 [inline]
 write_ports+0x526/0xb80 fs/nfsd/nfsctl.c:847
 nfsctl_transaction_write+0x105/0x150 fs/nfsd/nfsctl.c:114
 vfs_write+0x2dc/0x9a0 fs/read_write.c:582
 ksys_write+0x14d/0x260 fs/read_write.c:637
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Freed by task 4623:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:53
 kasan_save_free_info+0x27/0x40 mm/kasan/generic.c:516
 ____kasan_slab_free+0x126/0x1f0 mm/kasan/common.c:237
 kasan_slab_free include/linux/kasan.h:177 [inline]
 slab_free_hook mm/slub.c:1729 [inline]
 slab_free_freelist_hook+0x133/0x1b0 mm/slub.c:1755
 slab_free mm/slub.c:3687 [inline]
 __kmem_cache_free+0xb6/0x200 mm/slub.c:3700
 kref_put include/linux/kref.h:65 [inline]
 svc_put include/linux/sunrpc/svc.h:123 [inline]
 __write_ports_addfd fs/nfsd/nfsctl.c:728 [inline]
 __write_ports fs/nfsd/nfsctl.c:791 [inline]
 write_ports+0x9ac/0xb80 fs/nfsd/nfsctl.c:847
 nfsctl_transaction_write+0x105/0x150 fs/nfsd/nfsctl.c:114
 vfs_write+0x2dc/0x9a0 fs/read_write.c:582
 ksys_write+0x14d/0x260 fs/read_write.c:637
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

The buggy address belongs to the object at ffff88807b59b800
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 80 bytes inside of
 512-byte region [ffff88807b59b800, ffff88807b59ba00)

The buggy address belongs to the physical page:
page:ffffea0001ed6600 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x7b598
head:ffffea0001ed6600 order:2 compound_mapcount:0 compound_pincount:0
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000010200 ffffea0000a0ab00 dead000000000002 ffff888017441c80
raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 2, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 3639, tgid 3639 (udevd), ts 35973301978, free_ts 32140352358
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x173/0x1a0 mm/page_alloc.c:2560
 prep_new_page mm/page_alloc.c:2567 [inline]
 get_page_from_freelist+0x206b/0x2180 mm/page_alloc.c:4358
 __alloc_pages+0x1ec/0x4f0 mm/page_alloc.c:5658
 alloc_slab_page+0x5d/0x180 mm/slub.c:1799
 allocate_slab mm/slub.c:1944 [inline]
 new_slab+0x87/0x2d0 mm/slub.c:1997
 ___slab_alloc+0xbc5/0x1240 mm/slub.c:3154
 __slab_alloc mm/slub.c:3240 [inline]
 slab_alloc_node mm/slub.c:3325 [inline]
 __kmem_cache_alloc_node+0x126/0x270 mm/slub.c:3398
 __do_kmalloc_node mm/slab_common.c:935 [inline]
 __kmalloc_node_track_caller+0xa0/0x240 mm/slab_common.c:956
 kmalloc_reserve net/core/skbuff.c:446 [inline]
 __alloc_skb+0x226/0x7d0 net/core/skbuff.c:515
 alloc_skb include/linux/skbuff.h:1303 [inline]
 netlink_alloc_large_skb net/netlink/af_netlink.c:1182 [inline]
 netlink_sendmsg+0x654/0xbd0 net/netlink/af_netlink.c:1852
 sock_sendmsg_nosec net/socket.c:718 [inline]
 __sock_sendmsg net/socket.c:730 [inline]
 ____sys_sendmsg+0x5ed/0x9a0 net/socket.c:2519
 ___sys_sendmsg+0x2a2/0x360 net/socket.c:2573
 __sys_sendmsg net/socket.c:2602 [inline]
 __do_sys_sendmsg net/socket.c:2611 [inline]
 __se_sys_sendmsg+0x1c3/0x2b0 net/socket.c:2609
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1487 [inline]
 free_pcp_prepare mm/page_alloc.c:1537 [inline]
 free_unref_page_prepare+0x8e5/0x9e0 mm/page_alloc.c:3414
 free_unref_page+0x2e/0x3f0 mm/page_alloc.c:3509
 free_contig_range+0x9d/0x150 mm/page_alloc.c:9498
 destroy_args+0xef/0xa0e mm/debug_vm_pgtable.c:1031
 debug_vm_pgtable+0x33c/0x38e mm/debug_vm_pgtable.c:1359
 do_one_initcall+0x257/0x800 init/main.c:1271
 do_initcall_level+0x13d/0x1ed init/main.c:1344
 do_initcalls+0x4b/0x8a init/main.c:1360
 kernel_init_freeable+0x401/0x5ab init/main.c:1599
 kernel_init+0x19/0x1b0 init/main.c:1487
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

Memory state around the buggy address:
 ffff88807b59b700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88807b59b780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88807b59b800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                 ^
 ffff88807b59b880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88807b59b900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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