================================================================== 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_shutdown_threads+0x90/0x204 fs/nfsd/nfssvc.c:640 Write of size 4 at addr ffff0000f1de5450 by task syz-executor/4329 CPU: 0 PID: 4329 Comm: syz-executor Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/14/2026 Call trace: dump_backtrace+0x1c4/0x1f0 arch/arm64/kernel/stacktrace.c:158 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:165 __dump_stack+0x30/0x40 lib/dump_stack.c:88 dump_stack_lvl+0xf4/0x15c lib/dump_stack.c:106 print_address_description+0x88/0x218 mm/kasan/report.c:316 print_report+0x50/0x68 mm/kasan/report.c:420 kasan_report+0xa8/0xfc mm/kasan/report.c:524 check_region_inline mm/kasan/generic.c:-1 [inline] kasan_check_range+0x258/0x290 mm/kasan/generic.c:189 __kasan_check_write+0x2c/0x3c mm/kasan/shadow.c:37 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_shutdown_threads+0x90/0x204 fs/nfsd/nfssvc.c:640 nfsd_umount+0x48/0xf8 fs/nfsd/nfsctl.c:1409 deactivate_locked_super+0xb4/0x128 fs/super.c:332 deactivate_super+0xe4/0x104 fs/super.c:363 cleanup_mnt+0x3a8/0x430 fs/namespace.c:1191 __cleanup_mnt+0x20/0x30 fs/namespace.c:1198 task_work_run+0x1f4/0x280 kernel/task_work.c:203 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline] do_notify_resume+0x20f8/0x2c84 arch/arm64/kernel/signal.c:1151 prepare_exit_to_user_mode arch/arm64/kernel/entry-common.c:137 [inline] exit_to_user_mode arch/arm64/kernel/entry-common.c:142 [inline] el0_svc+0x9c/0x12c arch/arm64/kernel/entry-common.c:638 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585 Allocated by task 7691: kasan_save_stack mm/kasan/common.c:46 [inline] kasan_set_track+0x4c/0x80 mm/kasan/common.c:53 kasan_save_alloc_info+0x24/0x30 mm/kasan/generic.c:505 ____kasan_kmalloc mm/kasan/common.c:375 [inline] __kasan_kmalloc+0xa0/0xb8 mm/kasan/common.c:384 kasan_kmalloc include/linux/kasan.h:211 [inline] kmalloc_trace+0x7c/0x94 mm/slab_common.c:1031 kmalloc include/linux/slab.h:563 [inline] kzalloc include/linux/slab.h:699 [inline] __svc_create+0x80/0x89c net/sunrpc/svc.c:491 svc_create_pooled+0x648/0x7d8 net/sunrpc/svc.c:579 nfsd_create_serv+0x284/0x6a4 fs/nfsd/nfssvc.c:667 __write_ports_addfd fs/nfsd/nfsctl.c:716 [inline] __write_ports fs/nfsd/nfsctl.c:791 [inline] write_ports+0x3b8/0x9f0 fs/nfsd/nfsctl.c:847 nfsctl_transaction_write+0x114/0x164 fs/nfsd/nfsctl.c:114 vfs_write+0x2a8/0x7c8 fs/read_write.c:582 ksys_write+0x12c/0x228 fs/read_write.c:637 __do_sys_write fs/read_write.c:649 [inline] __se_sys_write fs/read_write.c:646 [inline] __arm64_sys_write+0x7c/0x90 fs/read_write.c:646 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline] invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52 el0_svc_common+0x13c/0x258 arch/arm64/kernel/syscall.c:140 do_el0_svc+0x5c/0x134 arch/arm64/kernel/syscall.c:204 el0_svc+0x58/0x12c arch/arm64/kernel/entry-common.c:637 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585 Freed by task 7691: kasan_save_stack mm/kasan/common.c:46 [inline] kasan_set_track+0x4c/0x80 mm/kasan/common.c:53 kasan_save_free_info+0x38/0x5c mm/kasan/generic.c:516 ____kasan_slab_free+0x148/0x1b0 mm/kasan/common.c:237 __kasan_slab_free+0x18/0x28 mm/kasan/common.c:245 kasan_slab_free include/linux/kasan.h:177 [inline] slab_free_hook mm/slub.c:1729 [inline] slab_free_freelist_hook+0x16c/0x1e8 mm/slub.c:1755 slab_free mm/slub.c:3687 [inline] __kmem_cache_free+0xbc/0x21c mm/slub.c:3700 kfree+0xd0/0x1a8 mm/slab_common.c:988 svc_destroy+0x144/0x184 net/sunrpc/svc.c:613 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+0x7dc/0x9f0 fs/nfsd/nfsctl.c:847 nfsctl_transaction_write+0x114/0x164 fs/nfsd/nfsctl.c:114 vfs_write+0x2a8/0x7c8 fs/read_write.c:582 ksys_write+0x12c/0x228 fs/read_write.c:637 __do_sys_write fs/read_write.c:649 [inline] __se_sys_write fs/read_write.c:646 [inline] __arm64_sys_write+0x7c/0x90 fs/read_write.c:646 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline] invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52 el0_svc_common+0x13c/0x258 arch/arm64/kernel/syscall.c:140 do_el0_svc+0x5c/0x134 arch/arm64/kernel/syscall.c:204 el0_svc+0x58/0x12c arch/arm64/kernel/entry-common.c:637 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585 Last potentially related work creation: kasan_save_stack+0x40/0x70 mm/kasan/common.c:46 __kasan_record_aux_stack+0xc0/0xdc mm/kasan/generic.c:486 kasan_record_aux_stack_noalloc+0x14/0x20 mm/kasan/generic.c:496 call_rcu+0x104/0x958 kernel/rcu/tree.c:2849 fib6_info_release include/net/ip6_fib.h:342 [inline] fixup_permanent_addr net/ipv6/addrconf.c:3554 [inline] addrconf_permanent_addr+0x2a4/0x870 net/ipv6/addrconf.c:3582 addrconf_notify+0x7b8/0xc98 net/ipv6/addrconf.c:3654 notifier_call_chain kernel/notifier.c:87 [inline] raw_notifier_call_chain+0xd8/0x168 kernel/notifier.c:455 call_netdevice_notifiers_info net/core/dev.c:2014 [inline] call_netdevice_notifiers_extack net/core/dev.c:2052 [inline] call_netdevice_notifiers net/core/dev.c:2066 [inline] __dev_notify_flags+0x260/0x490 net/core/dev.c:8716 dev_change_flags+0xd0/0x15c net/core/dev.c:8754 do_setlink+0x9d0/0x2158 net/core/rtnetlink.c:2845 __rtnl_newlink net/core/rtnetlink.c:3622 [inline] rtnl_newlink+0x142c/0x1af0 net/core/rtnetlink.c:3669 rtnetlink_rcv_msg+0x694/0xcc4 net/core/rtnetlink.c:6166 netlink_rcv_skb+0x220/0x3ec net/netlink/af_netlink.c:2516 rtnetlink_rcv+0x28/0x38 net/core/rtnetlink.c:6184 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline] netlink_unicast+0x5fc/0x80c net/netlink/af_netlink.c:1344 netlink_sendmsg+0x6f0/0x9d8 net/netlink/af_netlink.c:1877 sock_sendmsg_nosec net/socket.c:718 [inline] __sock_sendmsg net/socket.c:730 [inline] __sys_sendto+0x324/0x440 net/socket.c:2153 __do_sys_sendto net/socket.c:2165 [inline] __se_sys_sendto net/socket.c:2161 [inline] __arm64_sys_sendto+0xe4/0x104 net/socket.c:2161 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline] invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52 el0_svc_common+0x13c/0x258 arch/arm64/kernel/syscall.c:140 do_el0_svc+0x5c/0x134 arch/arm64/kernel/syscall.c:204 el0_svc+0x58/0x12c arch/arm64/kernel/entry-common.c:637 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585 The buggy address belongs to the object at ffff0000f1de5400 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 80 bytes inside of 512-byte region [ffff0000f1de5400, ffff0000f1de5600) The buggy address belongs to the physical page: page:0000000035f76503 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x131de4 head:0000000035f76503 order:2 compound_mapcount:0 compound_pincount:0 flags: 0x5ffc00000010200(slab|head|node=0|zone=2|lastcpupid=0x7ff) raw: 05ffc00000010200 0000000000000000 dead000000000001 ffff0000c0002600 raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff0000f1de5300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff0000f1de5380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffff0000f1de5400: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff0000f1de5480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff0000f1de5500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ================================================================== ------------[ cut here ]------------ refcount_t: addition on 0; use-after-free. WARNING: CPU: 1 PID: 4329 at lib/refcount.c:25 refcount_warn_saturate+0x134/0x1f8 lib/refcount.c:25 Modules linked in: CPU: 1 PID: 4329 Comm: syz-executor Tainted: G B syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/14/2026 pstate: 62400005 (nZCv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--) pc : refcount_warn_saturate+0x134/0x1f8 lib/refcount.c:25 lr : refcount_warn_saturate+0x134/0x1f8 lib/refcount.c:25 sp : ffff8000220b79b0 x29: ffff8000220b79b0 x28: ffff0000c085d980 x27: ffff0000c085d980 x26: dfff800000000000 x25: 0000000000000002 x24: 0000000000000002 x23: 0000000000000003 x22: 0000000000000000 x21: ffff0000f1de5400 x20: ffff0000f1de5450 x19: ffff800018dfb000 x18: 1fffe00033c1c97e x17: ffff80001641d000 x16: ffff800008043a58 x15: 0000000040000000 x14: 0000000000000001 x13: 1fffe00033c1f070 x12: 0000000000000000 x11: ff00800008048d3c x10: 0000000040000000 x9 : 66547609985af700 x8 : 66547609985af700 x7 : ffff800011d2c160 x6 : ffff80000825ab2c x5 : 0000000000000000 x4 : 0000000000000001 x3 : 0000000000000000 x2 : ffff8000220b7560 x1 : 0000000000000000 x0 : ffff80000825abc0 Call trace: refcount_warn_saturate+0x134/0x1f8 lib/refcount.c:25 __refcount_add include/linux/refcount.h:-1 [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_shutdown_threads+0x188/0x204 fs/nfsd/nfssvc.c:640 nfsd_umount+0x48/0xf8 fs/nfsd/nfsctl.c:1409 deactivate_locked_super+0xb4/0x128 fs/super.c:332 deactivate_super+0xe4/0x104 fs/super.c:363 cleanup_mnt+0x3a8/0x430 fs/namespace.c:1191 __cleanup_mnt+0x20/0x30 fs/namespace.c:1198 task_work_run+0x1f4/0x280 kernel/task_work.c:203 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline] do_notify_resume+0x20f8/0x2c84 arch/arm64/kernel/signal.c:1151 prepare_exit_to_user_mode arch/arm64/kernel/entry-common.c:137 [inline] exit_to_user_mode arch/arm64/kernel/entry-common.c:142 [inline] el0_svc+0x9c/0x12c arch/arm64/kernel/entry-common.c:638 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585 irq event stamp: 1747683 hardirqs last enabled at (1747683): [] raw_spin_rq_unlock_irq kernel/sched/sched.h:1374 [inline] hardirqs last enabled at (1747683): [] finish_lock_switch+0xb0/0x1c8 kernel/sched/core.c:5005 hardirqs last disabled at (1747682): [] __schedule+0x294/0x1a6c kernel/sched/core.c:6461 softirqs last enabled at (1747398): [] local_bh_enable+0x10/0x34 include/linux/bottom_half.h:32 softirqs last disabled at (1747396): [] local_bh_disable+0x10/0x34 include/linux/bottom_half.h:19 ---[ end trace 0000000000000000 ]--- Unable to handle kernel paging request at virtual address dfff800000000006 KASAN: null-ptr-deref in range [0x0000000000000030-0x0000000000000037] Mem abort info: ESR = 0x0000000096000006 EC = 0x25: DABT (current EL), IL = 32 bits SET = 0, FnV = 0 EA = 0, S1PTW = 0 FSC = 0x06: level 2 translation fault Data abort info: ISV = 0, ISS = 0x00000006 CM = 0, WnR = 0 [dfff800000000006] address between user and kernel address ranges Internal error: Oops: 0000000096000006 [#1] PREEMPT SMP Modules linked in: CPU: 0 PID: 4329 Comm: syz-executor Tainted: G B W syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/14/2026 pstate: 02400005 (nzcv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--) pc : svc_unregister+0x130/0x624 net/sunrpc/svc.c:1170 lr : svc_unregister+0x120/0x624 net/sunrpc/svc.c:1168 sp : ffff8000220b78d0 x29: ffff8000220b7900 x28: dfff800000000000 x27: ffff0000f1c970f8 x26: ffff0000d30a8000 x25: 0000000000000030 x24: 000000000000001c x23: ffff0000f1c970f4 x22: 1fffe0001e392e1e x21: ffff0000f1c970e0 x20: 1fffe0001e392e1f x19: 00000000000000e0 x18: 1fffe00033c1877e x17: ffff80001641d000 x16: ffff800011bcb318 x15: 0000000000000000 x14: 0000000011bc78f8 x13: 00000000f76ee403 x12: ffff800008021d48 x11: ff00800010f3db90 x10: 0000000000000000 x9 : ffff80001d6b7910 x8 : 0000000000000006 x7 : 0000000000000000 x6 : 000000000000003f x5 : 0000000000000040 x4 : 0000000000000001 x3 : ffff800010f3d9f0 x2 : 0000000000000000 x1 : 0000000000000008 x0 : 0000000000000000 Call trace: svc_unregister+0x130/0x624 net/sunrpc/svc.c:1170 svc_rpcb_cleanup+0x28/0x40 net/sunrpc/svc.c:434 nfsd_last_thread+0x114/0x2e4 fs/nfsd/nfssvc.c:560 nfsd_shutdown_threads+0xe4/0x204 fs/nfsd/nfssvc.c:643 nfsd_umount+0x48/0xf8 fs/nfsd/nfsctl.c:1409 deactivate_locked_super+0xb4/0x128 fs/super.c:332 deactivate_super+0xe4/0x104 fs/super.c:363 cleanup_mnt+0x3a8/0x430 fs/namespace.c:1191 __cleanup_mnt+0x20/0x30 fs/namespace.c:1198 task_work_run+0x1f4/0x280 kernel/task_work.c:203 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline] do_notify_resume+0x20f8/0x2c84 arch/arm64/kernel/signal.c:1151 prepare_exit_to_user_mode arch/arm64/kernel/entry-common.c:137 [inline] exit_to_user_mode arch/arm64/kernel/entry-common.c:142 [inline] el0_svc+0x9c/0x12c arch/arm64/kernel/entry-common.c:638 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585 Code: f8736b28 b4000148 91007119 d343ff28 (38fc6908) ---[ end trace 0000000000000000 ]--- ---------------- Code disassembly (best guess): 0: f8736b28 ldr x8, [x25, x19] 4: b4000148 cbz x8, 0x2c 8: 91007119 add x25, x8, #0x1c c: d343ff28 lsr x8, x25, #3 * 10: 38fc6908 ldrsb w8, [x8, x28] <-- trapping instruction