================================================================== BUG: KASAN: use-after-free in nfsd_svc+0x818/0x948 fs/nfsd/nfssvc.c:813 Read of size 4 at addr ffff0000f4d4e854 by task syz.0.1967/9739 CPU: 1 PID: 9739 Comm: syz.0.1967 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 __asan_report_load4_noabort+0x2c/0x38 mm/kasan/report_generic.c:350 nfsd_svc+0x818/0x948 fs/nfsd/nfssvc.c:813 write_threads+0x2b4/0x310 fs/nfsd/nfsctl.c:424 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+0x58/0x128 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 Allocated by task 9739: 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 nfsd_svc+0x168/0x948 fs/nfsd/nfssvc.c:796 write_threads+0x2b4/0x310 fs/nfsd/nfsctl.c:424 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+0x58/0x128 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 9739: 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] nfsd_svc+0x63c/0x948 fs/nfsd/nfssvc.c:811 write_threads+0x2b4/0x310 fs/nfsd/nfsctl.c:424 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+0x58/0x128 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] nsim_rt6_release drivers/net/netdevsim/fib.c:515 [inline] nsim_fib6_event_fini+0x100/0x208 drivers/net/netdevsim/fib.c:841 nsim_fib_event drivers/net/netdevsim/fib.c:891 [inline] nsim_fib_event_work+0x2ec/0x2708 drivers/net/netdevsim/fib.c:1494 process_one_work+0x7e4/0x13bc kernel/workqueue.c:2292 process_scheduled_works kernel/workqueue.c:2355 [inline] worker_thread+0xafc/0xfe8 kernel/workqueue.c:2441 kthread+0x254/0x2e0 kernel/kthread.c:376 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:850 The buggy address belongs to the object at ffff0000f4d4e800 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 84 bytes inside of 512-byte region [ffff0000f4d4e800, ffff0000f4d4ea00) The buggy address belongs to the physical page: page:000000006e537dce refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x134d4c head:000000006e537dce 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: ffff0000f4d4e700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff0000f4d4e780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffff0000f4d4e800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff0000f4d4e880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff0000f4d4e900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ================================================================== Unable to handle kernel paging request at virtual address dfff800000000000 KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] 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 [dfff800000000000] address between user and kernel address ranges Internal error: Oops: 0000000096000006 [#1] PREEMPT SMP Modules linked in: CPU: 0 PID: 9739 Comm: syz.0.1967 Tainted: G B 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+0x110/0x624 net/sunrpc/svc.c:1168 lr : svc_unregister+0x104/0x624 net/sunrpc/svc.c:1168 sp : ffff800021b07820 x29: ffff800021b07850 x28: dfff800000000000 x27: ffff0000c42ce018 x26: ffff0000d6610000 x25: 0000000000000000 x24: 0000000000000000 x23: ffff0000c42ce014 x22: 1fffe00018859c02 x21: ffff0000c42ce000 x20: 1fffe00018859c03 x19: 0000000000000000 x18: 1fffe00033e6997e x17: ffff8000153bd000 x16: ffff800008043b30 x15: ffff00019f34cbfc x14: 0000000000000001 x13: 1fffe0001a95d380 x12: 0000000000080000 x11: ff00800010f2ca94 x10: 0000000000000002 x9 : ffff80001c635b50 x8 : 0000000000000000 x7 : 0000000000000000 x6 : ffff800010f70810 x5 : 0000000000000000 x4 : 0000000000000001 x3 : ffff800010f2cad0 x2 : 0000000000000000 x1 : 0000000000000008 x0 : 0000000000000000 Call trace: svc_unregister+0x110/0x624 net/sunrpc/svc.c:1168 svc_rpcb_cleanup+0x28/0x40 net/sunrpc/svc.c:434 nfsd_last_thread+0x114/0x2e4 fs/nfsd/nfssvc.c:560 nfsd_svc+0x698/0x948 fs/nfsd/nfssvc.c:814 write_threads+0x2b4/0x310 fs/nfsd/nfsctl.c:424 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+0x58/0x128 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 Code: 97c321b8 f9400379 8b190268 d343fd08 (387c6908) ---[ end trace 0000000000000000 ]--- ---------------- Code disassembly (best guess): 0: 97c321b8 bl 0xffffffffff0c86e0 4: f9400379 ldr x25, [x27] 8: 8b190268 add x8, x19, x25 c: d343fd08 lsr x8, x8, #3 * 10: 387c6908 ldrb w8, [x8, x28] <-- trapping instruction