================================================================== BUG: KASAN: slab-use-after-free in __hlist_del include/linux/list.h:992 [inline] BUG: KASAN: slab-use-after-free in hlist_del_init_rcu include/linux/rculist.h:238 [inline] BUG: KASAN: slab-use-after-free in ipv6_del_acaddr_hash net/ipv6/anycast.c:254 [inline] BUG: KASAN: slab-use-after-free in __ipv6_dev_ac_dec+0x4c2/0x690 net/ipv6/anycast.c:419 Write of size 8 at addr ffff8880227da420 by task syz.0.4580/20671 CPU: 1 UID: 0 PID: 20671 Comm: syz.0.4580 Tainted: G L syzkaller #0 PREEMPT(full) Tainted: [L]=SOFTLOCKUP Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026 Call Trace: dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 print_address_description+0x55/0x1e0 mm/kasan/report.c:378 print_report+0x58/0x70 mm/kasan/report.c:482 kasan_report+0x117/0x150 mm/kasan/report.c:595 __hlist_del include/linux/list.h:992 [inline] hlist_del_init_rcu include/linux/rculist.h:238 [inline] ipv6_del_acaddr_hash net/ipv6/anycast.c:254 [inline] __ipv6_dev_ac_dec+0x4c2/0x690 net/ipv6/anycast.c:419 ipv6_dev_ac_dec net/ipv6/anycast.c:438 [inline] __ipv6_sock_ac_close+0x24e/0x430 net/ipv6/anycast.c:224 inet6_release+0x4f/0x70 net/ipv6/af_inet6.c:470 __sock_release net/socket.c:722 [inline] sock_close+0xc3/0x240 net/socket.c:1514 __fput+0x44f/0xa60 fs/file_table.c:510 task_work_run+0x1d9/0x270 kernel/task_work.c:233 exit_task_work include/linux/task_work.h:40 [inline] do_exit+0x70f/0x22c0 kernel/exit.c:975 do_group_exit+0x21b/0x2d0 kernel/exit.c:1117 get_signal+0x1284/0x1330 kernel/signal.c:3037 arch_do_signal_or_restart+0xbc/0x830 arch/x86/kernel/signal.c:337 __exit_to_user_mode_loop kernel/entry/common.c:64 [inline] exit_to_user_mode_loop+0x86/0x480 kernel/entry/common.c:98 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline] syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:238 [inline] syscall_exit_to_user_mode include/linux/entry-common.h:318 [inline] do_syscall_64+0x33e/0xf80 arch/x86/entry/syscall_64.c:100 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f234d79cdd9 Code: Unable to access opcode bytes at 0x7f234d79cdaf. RSP: 002b:00007f234e69b028 EFLAGS: 00000246 ORIG_RAX: 000000000000012b RAX: 0000000000010106 RBX: 00007f234da16090 RCX: 00007f234d79cdd9 RDX: 0000000000010106 RSI: 00002000000000c0 RDI: 0000000000000006 RBP: 00007f234d832d69 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000002 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f234da16128 R14: 00007f234da16090 R15: 00007f234db3fa48 Allocated by task 20672: kasan_save_stack mm/kasan/common.c:57 [inline] kasan_save_track+0x3e/0x80 mm/kasan/common.c:78 poison_kmalloc_redzone mm/kasan/common.c:398 [inline] __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:415 kasan_kmalloc include/linux/kasan.h:263 [inline] __kmalloc_cache_noprof+0x31c/0x660 mm/slub.c:5419 kmalloc_noprof include/linux/slab.h:950 [inline] kzalloc_noprof include/linux/slab.h:1188 [inline] aca_alloc net/ipv6/anycast.c:282 [inline] __ipv6_dev_ac_inc+0x37f/0xaf0 net/ipv6/anycast.c:360 ipv6_sock_ac_join+0x6a8/0x880 net/ipv6/anycast.c:153 do_ipv6_setsockopt+0x203a/0x3150 net/ipv6/ipv6_sockglue.c:893 ipv6_setsockopt+0x59/0x170 net/ipv6/ipv6_sockglue.c:965 do_sock_setsockopt+0x17c/0x1b0 net/socket.c:2381 __sys_setsockopt net/socket.c:2406 [inline] __do_sys_setsockopt net/socket.c:2412 [inline] __se_sys_setsockopt net/socket.c:2409 [inline] __x64_sys_setsockopt+0x13d/0x1b0 net/socket.c:2409 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f Freed by task 23: kasan_save_stack mm/kasan/common.c:57 [inline] kasan_save_track+0x3e/0x80 mm/kasan/common.c:78 kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:584 poison_slab_object mm/kasan/common.c:253 [inline] __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:285 kasan_slab_free include/linux/kasan.h:235 [inline] slab_free_hook mm/slub.c:2689 [inline] slab_free mm/slub.c:6250 [inline] kfree+0x1c5/0x640 mm/slub.c:6565 rcu_do_batch kernel/rcu/tree.c:2617 [inline] rcu_core+0x7cd/0x1070 kernel/rcu/tree.c:2869 handle_softirqs+0x22a/0x840 kernel/softirq.c:622 run_ksoftirqd+0x36/0x60 kernel/softirq.c:1076 smpboot_thread_fn+0x541/0xa50 kernel/smpboot.c:160 kthread+0x388/0x470 kernel/kthread.c:436 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 Last potentially related work creation: kasan_save_stack+0x3e/0x60 mm/kasan/common.c:57 kasan_record_aux_stack+0xbd/0xd0 mm/kasan/generic.c:556 __call_rcu_common kernel/rcu/tree.c:3131 [inline] call_rcu+0xee/0x890 kernel/rcu/tree.c:3251 call_rcu_hurry include/linux/rcupdate.h:125 [inline] aca_put net/ipv6/anycast.c:274 [inline] __ipv6_dev_ac_inc+0x8e0/0xaf0 net/ipv6/anycast.c:384 ipv6_sock_ac_join+0x6a8/0x880 net/ipv6/anycast.c:153 do_ipv6_setsockopt+0x203a/0x3150 net/ipv6/ipv6_sockglue.c:893 ipv6_setsockopt+0x59/0x170 net/ipv6/ipv6_sockglue.c:965 do_sock_setsockopt+0x17c/0x1b0 net/socket.c:2381 __sys_setsockopt net/socket.c:2406 [inline] __do_sys_setsockopt net/socket.c:2412 [inline] __se_sys_setsockopt net/socket.c:2409 [inline] __x64_sys_setsockopt+0x13d/0x1b0 net/socket.c:2409 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f The buggy address belongs to the object at ffff8880227da400 which belongs to the cache kmalloc-96 of size 96 The buggy address is located 32 bytes inside of freed 96-byte region [ffff8880227da400, ffff8880227da460) The buggy address belongs to the physical page: page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x227da flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff) page_type: f5(slab) raw: 00fff00000000000 ffff88813fe19280 dead000000000100 dead000000000122 raw: 0000000000000000 0000000800200020 00000000f5000000 0000000000000000 page dumped because: kasan: bad access detected page_owner tracks the page as allocated page last allocated via order 0, migratetype Unmovable, gfp_mask 0xd2820(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 57, tgid 57 (kworker/u8:4), ts 95690583368, free_ts 95636416997 set_page_owner include/linux/page_owner.h:32 [inline] post_alloc_hook+0x231/0x280 mm/page_alloc.c:1858 prep_new_page mm/page_alloc.c:1866 [inline] get_page_from_freelist+0x24ba/0x2540 mm/page_alloc.c:3946 __alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5226 alloc_slab_page mm/slub.c:3278 [inline] allocate_slab+0x77/0x660 mm/slub.c:3467 new_slab mm/slub.c:3525 [inline] refill_objects+0x339/0x3d0 mm/slub.c:7255 refill_sheaf mm/slub.c:2816 [inline] __pcs_replace_empty_main+0x321/0x720 mm/slub.c:4651 alloc_from_pcs mm/slub.c:4749 [inline] slab_alloc_node mm/slub.c:4883 [inline] __kmalloc_cache_noprof+0x392/0x660 mm/slub.c:5414 kmalloc_noprof include/linux/slab.h:950 [inline] dst_cow_metrics_generic+0x56/0x1c0 net/core/dst.c:194 dst_metrics_write_ptr include/net/dst.h:136 [inline] dst_metric_set include/net/dst.h:197 [inline] icmp6_dst_alloc+0x265/0x440 net/ipv6/route.c:3350 mld_sendpack+0x6ba/0xe40 net/ipv6/mcast.c:1844 ipv6_mc_dad_complete+0x88/0x540 net/ipv6/mcast.c:2279 addrconf_dad_completed+0x8a7/0xe60 net/ipv6/addrconf.c:4352 addrconf_dad_work+0xc5e/0x14c0 net/ipv6/addrconf.c:-1 process_one_work kernel/workqueue.c:3302 [inline] process_scheduled_works+0xb5d/0x1860 kernel/workqueue.c:3385 worker_thread+0xa53/0xfc0 kernel/workqueue.c:3466 kthread+0x388/0x470 kernel/kthread.c:436 page last free pid 5647 tgid 5647 stack trace: reset_page_owner include/linux/page_owner.h:25 [inline] __free_pages_prepare mm/page_alloc.c:1402 [inline] __free_frozen_pages+0xbc7/0xd30 mm/page_alloc.c:2943 __tlb_remove_table_free mm/mmu_gather.c:228 [inline] tlb_remove_table_rcu+0x85/0x100 mm/mmu_gather.c:291 rcu_do_batch kernel/rcu/tree.c:2617 [inline] rcu_core+0x7cd/0x1070 kernel/rcu/tree.c:2869 handle_softirqs+0x22a/0x840 kernel/softirq.c:622 __do_softirq kernel/softirq.c:656 [inline] invoke_softirq kernel/softirq.c:496 [inline] __irq_exit_rcu+0xca/0x220 kernel/softirq.c:735 irq_exit_rcu+0x9/0x30 kernel/softirq.c:752 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1061 [inline] sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1061 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697 Memory state around the buggy address: ffff8880227da300: 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc ffff8880227da380: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc >ffff8880227da400: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc ^ ffff8880227da480: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc ffff8880227da500: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc ==================================================================