==================================================================
BUG: KASAN: slab-use-after-free in instrument_atomic_read_write include/linux/instrumented.h:96 [inline]
BUG: KASAN: slab-use-after-free in atomic_fetch_add_relaxed include/linux/atomic/atomic-instrumented.h:252 [inline]
BUG: KASAN: slab-use-after-free in __refcount_add include/linux/refcount.h:193 [inline]
BUG: KASAN: slab-use-after-free in __refcount_inc include/linux/refcount.h:250 [inline]
BUG: KASAN: slab-use-after-free in refcount_inc include/linux/refcount.h:267 [inline]
BUG: KASAN: slab-use-after-free in kref_get include/linux/kref.h:45 [inline]
BUG: KASAN: slab-use-after-free in svc_get include/linux/sunrpc/svc.h:109 [inline]
BUG: KASAN: slab-use-after-free in nfsd_shutdown_threads+0x8d/0x1a0 fs/nfsd/nfssvc.c:645
Write of size 4 at addr ffff888024eb7050 by task syz-executor/19527

CPU: 1 PID: 19527 Comm: syz-executor Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:364 [inline]
 print_report+0xa8/0x210 mm/kasan/report.c:468
 kasan_report+0x117/0x150 mm/kasan/report.c:581
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x241/0x290 mm/kasan/generic.c:187
 instrument_atomic_read_write include/linux/instrumented.h:96 [inline]
 atomic_fetch_add_relaxed include/linux/atomic/atomic-instrumented.h:252 [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:109 [inline]
 nfsd_shutdown_threads+0x8d/0x1a0 fs/nfsd/nfssvc.c:645
 nfsd_umount+0x42/0xc0 fs/nfsd/nfsctl.c:1464
 deactivate_locked_super+0x97/0x100 fs/super.c:481
 cleanup_mnt+0x3d7/0x460 fs/namespace.c:1259
 task_work_run+0x1d4/0x260 kernel/task_work.c:245
 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
 exit_to_user_mode_loop+0xe6/0x110 kernel/entry/common.c:177
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
 do_syscall_64+0x61/0xb0 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fe961d9f317
Code: a2 c7 05 dc 43 25 00 00 00 00 00 eb 96 e8 e1 12 00 00 90 31 f6 e9 09 00 00 00 66 0f 1f 84 00 00 00 00 00 b8 a6 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 01 c3 48 c7 c2 e8 ff ff ff f7 d8 64 89 02 b8
RSP: 002b:00007ffd3696adf8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
RAX: 0000000000000000 RBX: 00007fe961e34474 RCX: 00007fe961d9f317
RDX: 0000000000000000 RSI: 0000000000000009 RDI: 00007ffd3696aeb0
RBP: 00007ffd3696aeb0 R08: 00007ffd3696beb0 R09: 00000000ffffffff
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffd3696bf40
R13: 00007fe961e34474 R14: 0000000000095eb9 R15: 00007ffd3696bf80
 </TASK>

Allocated by task 20211:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:53
 ____kasan_kmalloc mm/kasan/common.c:375 [inline]
 __kasan_kmalloc+0x8f/0xa0 mm/kasan/common.c:384
 kmalloc include/linux/slab.h:600 [inline]
 kzalloc include/linux/slab.h:721 [inline]
 __svc_create+0x60/0xa20 net/sunrpc/svc.c:464
 svc_create_pooled+0x66a/0x7e0 net/sunrpc/svc.c:556
 nfsd_create_serv+0x29f/0x5c0 fs/nfsd/nfssvc.c:672
 __write_ports_addfd fs/nfsd/nfsctl.c:712 [inline]
 __write_ports fs/nfsd/nfsctl.c:788 [inline]
 write_ports+0x698/0xfa0 fs/nfsd/nfsctl.c:844
 nfsctl_transaction_write+0x10c/0x150 fs/nfsd/nfsctl.c:113
 vfs_write+0x299/0x9a0 fs/read_write.c:582
 ksys_write+0x151/0x260 fs/read_write.c:637
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Freed by task 20211:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:53
 kasan_save_free_info+0x28/0x40 mm/kasan/generic.c:522
 ____kasan_slab_free+0x126/0x1f0 mm/kasan/common.c:237
 kasan_slab_free include/linux/kasan.h:164 [inline]
 slab_free_hook mm/slub.c:1811 [inline]
 slab_free_freelist_hook+0x130/0x1a0 mm/slub.c:1837
 slab_free mm/slub.c:3830 [inline]
 __kmem_cache_free+0xba/0x1f0 mm/slub.c:3843
 kref_put include/linux/kref.h:65 [inline]
 svc_put include/linux/sunrpc/svc.h:124 [inline]
 __write_ports_addfd fs/nfsd/nfsctl.c:724 [inline]
 __write_ports fs/nfsd/nfsctl.c:788 [inline]
 write_ports+0xb1a/0xfa0 fs/nfsd/nfsctl.c:844
 nfsctl_transaction_write+0x10c/0x150 fs/nfsd/nfsctl.c:113
 vfs_write+0x299/0x9a0 fs/read_write.c:582
 ksys_write+0x151/0x260 fs/read_write.c:637
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Last potentially related work creation:
 kasan_save_stack+0x3e/0x60 mm/kasan/common.c:46
 __kasan_record_aux_stack+0xaf/0xc0 mm/kasan/generic.c:492
 kvfree_call_rcu+0xee/0x780 kernel/rcu/tree.c:3452
 __ipv6_dev_mc_dec+0x2e6/0x340 net/ipv6/mcast.c:988
 ipv6_mc_destroy_dev+0x336/0x590 net/ipv6/mcast.c:2837
 addrconf_ifdown+0x13b8/0x18a0 net/ipv6/addrconf.c:3998
 addrconf_notify+0x6c6/0x1010 net/ipv6/addrconf.c:-1
 notifier_call_chain+0x18f/0x380 kernel/notifier.c:93
 call_netdevice_notifiers_extack net/core/dev.c:2077 [inline]
 call_netdevice_notifiers net/core/dev.c:2091 [inline]
 unregister_netdevice_many_notify+0x1037/0x1910 net/core/dev.c:11124
 unregister_netdevice_many net/core/dev.c:11180 [inline]
 default_device_exit_batch+0x962/0xa00 net/core/dev.c:11746
 ops_exit_list net/core/net_namespace.c:178 [inline]
 cleanup_net+0x792/0xbb0 net/core/net_namespace.c:652
 process_one_work kernel/workqueue.c:2657 [inline]
 process_scheduled_works+0xa60/0x1600 kernel/workqueue.c:2734
 worker_thread+0xa5e/0xfe0 kernel/workqueue.c:2815
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293

Second to last potentially related work creation:
 kasan_save_stack+0x3e/0x60 mm/kasan/common.c:46
 __kasan_record_aux_stack+0xaf/0xc0 mm/kasan/generic.c:492
 __call_rcu_common kernel/rcu/tree.c:2721 [inline]
 call_rcu+0x153/0x900 kernel/rcu/tree.c:2837
 fib6_info_release include/net/ip6_fib.h:349 [inline]
 fib6_del_route net/ipv6/ip6_fib.c:2021 [inline]
 fib6_del+0x1163/0x1590 net/ipv6/ip6_fib.c:2054
 fib6_clean_node+0x290/0x540 net/ipv6/ip6_fib.c:2216
 fib6_walk_continue+0x67f/0x8d0 net/ipv6/ip6_fib.c:2138
 fib6_walk+0x149/0x270 net/ipv6/ip6_fib.c:2186
 fib6_clean_tree net/ipv6/ip6_fib.c:2266 [inline]
 __fib6_clean_all+0x27e/0x3e0 net/ipv6/ip6_fib.c:2282
 rt6_sync_down_dev net/ipv6/route.c:4953 [inline]
 rt6_disable_ip+0x12a/0x860 net/ipv6/route.c:4958
 addrconf_ifdown+0x160/0x18a0 net/ipv6/addrconf.c:3855
 addrconf_notify+0x6c6/0x1010 net/ipv6/addrconf.c:-1
 notifier_call_chain+0x18f/0x380 kernel/notifier.c:93
 call_netdevice_notifiers_extack net/core/dev.c:2077 [inline]
 call_netdevice_notifiers net/core/dev.c:2091 [inline]
 dev_close_many+0x2a6/0x410 net/core/dev.c:1632
 unregister_netdevice_many_notify+0x4bf/0x1910 net/core/dev.c:11097
 unregister_netdevice_many net/core/dev.c:11180 [inline]
 default_device_exit_batch+0x962/0xa00 net/core/dev.c:11746
 ops_exit_list net/core/net_namespace.c:178 [inline]
 cleanup_net+0x792/0xbb0 net/core/net_namespace.c:652
 process_one_work kernel/workqueue.c:2657 [inline]
 process_scheduled_works+0xa60/0x1600 kernel/workqueue.c:2734
 worker_thread+0xa5e/0xfe0 kernel/workqueue.c:2815
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293

The buggy address belongs to the object at ffff888024eb7000
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 80 bytes inside of
 freed 512-byte region [ffff888024eb7000, ffff888024eb7200)

The buggy address belongs to the physical page:
page:ffffea000093ad00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x24eb4
head:ffffea000093ad00 order:2 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000840(slab|head|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000840 ffff888017c41c80 dead000000000100 dead000000000122
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 0x1d20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 8105, tgid 8105 (syz-executor), ts 240117576091, free_ts 138035851034
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x1c1/0x200 mm/page_alloc.c:1582
 prep_new_page mm/page_alloc.c:1589 [inline]
 get_page_from_freelist+0x2181/0x22a0 mm/page_alloc.c:3221
 __alloc_pages+0x1f0/0x460 mm/page_alloc.c:4501
 alloc_slab_page+0x5d/0x180 mm/slub.c:1881
 allocate_slab mm/slub.c:2028 [inline]
 new_slab+0x87/0x2d0 mm/slub.c:2081
 ___slab_alloc+0xc5c/0x12f0 mm/slub.c:3253
 __slab_alloc mm/slub.c:3339 [inline]
 __slab_alloc_node mm/slub.c:3392 [inline]
 slab_alloc_node mm/slub.c:3485 [inline]
 __kmem_cache_alloc_node+0x11f/0x250 mm/slub.c:3534
 __do_kmalloc_node mm/slab_common.c:1006 [inline]
 __kmalloc+0xa7/0x240 mm/slab_common.c:1020
 kmalloc include/linux/slab.h:604 [inline]
 kzalloc include/linux/slab.h:721 [inline]
 fib6_info_alloc+0x30/0xf0 net/ipv6/ip6_fib.c:155
 ip6_route_info_create+0x455/0x1260 net/ipv6/route.c:3805
 addrconf_f6i_alloc+0x1fa/0x440 net/ipv6/route.c:4633
 ipv6_add_addr+0x5a4/0x10d0 net/ipv6/addrconf.c:1129
 inet6_addr_add+0x563/0xb30 net/ipv6/addrconf.c:3061
 inet6_rtm_newaddr+0x6fd/0x9d0 net/ipv6/addrconf.c:5043
 rtnetlink_rcv_msg+0x843/0xf90 net/core/rtnetlink.c:6484
 netlink_rcv_skb+0x235/0x4c0 net/netlink/af_netlink.c:2550
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1182 [inline]
 free_unref_page_prepare+0x7d7/0x8f0 mm/page_alloc.c:2366
 free_unref_page+0x32/0x2e0 mm/page_alloc.c:2459
 discard_slab mm/slub.c:2127 [inline]
 __unfreeze_partials+0x1cf/0x210 mm/slub.c:2667
 put_cpu_partial+0x17c/0x250 mm/slub.c:2743
 __slab_free+0x319/0x400 mm/slub.c:3700
 qlink_free mm/kasan/quarantine.c:166 [inline]
 qlist_free_all+0x75/0xd0 mm/kasan/quarantine.c:185
 kasan_quarantine_reduce+0x143/0x160 mm/kasan/quarantine.c:292
 __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:306
 kasan_slab_alloc include/linux/kasan.h:188 [inline]
 slab_post_alloc_hook+0x6a/0x4d0 mm/slab.h:770
 slab_alloc_node mm/slub.c:3495 [inline]
 slab_alloc mm/slub.c:3503 [inline]
 __kmem_cache_alloc_lru mm/slub.c:3510 [inline]
 kmem_cache_alloc+0x17e/0x2c0 mm/slub.c:3519
 getname_flags+0xbb/0x500 fs/namei.c:140
 do_sys_openat2+0xda/0x1d0 fs/open.c:1416
 do_sys_open fs/open.c:1437 [inline]
 __do_sys_openat fs/open.c:1453 [inline]
 __se_sys_openat fs/open.c:1448 [inline]
 __x64_sys_openat+0x139/0x160 fs/open.c:1448
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Memory state around the buggy address:
 ffff888024eb6f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888024eb6f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888024eb7000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                 ^
 ffff888024eb7080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888024eb7100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================