================================================================== BUG: KASAN: use-after-free in rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75 Read of size 8 at addr ffff88811ece3990 by task syz.4.680/2764 CPU: 1 PID: 2764 Comm: syz.4.680 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026 Call Trace: __dump_stack+0x21/0x24 lib/dump_stack.c:77 dump_stack_lvl+0x1a7/0x208 lib/dump_stack.c:118 print_address_description+0x7f/0x2c0 mm/kasan/report.c:248 __kasan_report mm/kasan/report.c:435 [inline] kasan_report+0x100/0x140 mm/kasan/report.c:452 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report_generic.c:309 rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75 rcu_do_batch+0x448/0xaf0 kernel/rcu/tree.c:2484 rcu_core+0x50a/0xca0 kernel/rcu/tree.c:2735 rcu_core_si+0x9/0x10 kernel/rcu/tree.c:2748 __do_softirq+0x255/0x563 kernel/softirq.c:309 asm_call_irq_on_stack+0xf/0x20 __run_on_irqstack arch/x86/include/asm/irq_stack.h:26 [inline] run_on_irqstack_cond arch/x86/include/asm/irq_stack.h:77 [inline] do_softirq_own_stack+0x60/0x80 arch/x86/kernel/irq_64.c:77 invoke_softirq kernel/softirq.c:405 [inline] __irq_exit_rcu+0x128/0x150 kernel/softirq.c:435 irq_exit_rcu+0x9/0x10 kernel/softirq.c:447 sysvec_apic_timer_interrupt+0xbf/0xe0 arch/x86/kernel/apic/apic.c:1106 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:635 RIP: 0010:preempt_count arch/x86/include/asm/preempt.h:26 [inline] RIP: 0010:check_kcov_mode kernel/kcov.c:163 [inline] RIP: 0010:__sanitizer_cov_trace_pc+0x10/0x60 kernel/kcov.c:197 Code: 89 fb e8 13 00 00 00 48 8b 3d ec ca 5e 05 48 89 de e8 c4 d6 39 00 5b 5d c3 00 55 48 89 e5 48 8b 45 08 65 48 8b 0d 90 c7 9d 7e <65> 8b 15 95 c7 9d 7e f7 c2 00 01 ff 00 74 11 f7 c2 00 01 00 00 74 RSP: 0018:ffffc90000fb7d78 EFLAGS: 00000202 RAX: ffffffff812ffb38 RBX: 000000010aba1230 RCX: ffff8881339e8000 RDX: 0000000000000002 RSI: 0000000000000008 RDI: 0000000000000000 RBP: ffffc90000fb7d78 R08: ffff8881339e8000 R09: 0000000000000002 R10: 0000000000000001 R11: 0000000000000002 R12: 0000000000000008 R13: dffffc0000000000 R14: ffff88823fff5420 R15: dffffc0000000000 pfn_valid include/linux/mmzone.h:1658 [inline] __virt_addr_valid+0x218/0x2b0 arch/x86/mm/physaddr.c:65 check_heap_object mm/usercopy.c:228 [inline] __check_object_size+0xa5/0x3b0 mm/usercopy.c:286 check_object_size include/linux/thread_info.h:132 [inline] check_copy_size include/linux/thread_info.h:165 [inline] copy_from_user include/linux/uaccess.h:191 [inline] memdup_user mm/util.c:180 [inline] strndup_user+0xa3/0x150 mm/util.c:235 copy_mount_string fs/namespace.c:3244 [inline] __do_sys_mount fs/namespace.c:3542 [inline] __se_sys_mount+0x9c/0x390 fs/namespace.c:3534 __x64_sys_mount+0xbf/0xd0 fs/namespace.c:3534 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x61/0xcb RIP: 0033:0x7f97229410d9 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:00007f972139a028 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5 RAX: ffffffffffffffda RBX: 00007f9722bc8fa0 RCX: 00007f97229410d9 RDX: 0000200000000180 RSI: 0000200000000000 RDI: 0000000000000000 RBP: 00007f97229d8024 R08: 0000200000000380 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f9722bc9038 R14: 00007f9722bc8fa0 R15: 00007fff584f2a38 Allocated by task 2760: kasan_save_stack mm/kasan/common.c:38 [inline] kasan_set_track mm/kasan/common.c:45 [inline] set_alloc_info mm/kasan/common.c:430 [inline] ____kasan_kmalloc mm/kasan/common.c:509 [inline] __kasan_kmalloc+0xd4/0x100 mm/kasan/common.c:518 kasan_kmalloc include/linux/kasan.h:254 [inline] __kmalloc+0x19f/0x330 mm/slub.c:4038 kmalloc include/linux/slab.h:560 [inline] kzalloc include/linux/slab.h:667 [inline] l2tp_session_create+0x39/0xb60 net/l2tp/l2tp_core.c:1616 pppol2tp_connect+0xbf5/0x1640 net/l2tp/l2tp_ppp.c:772 __sys_connect_file net/socket.c:1867 [inline] __sys_connect+0x3ce/0x450 net/socket.c:1884 __do_sys_connect net/socket.c:1894 [inline] __se_sys_connect net/socket.c:1891 [inline] __x64_sys_connect+0x7a/0x90 net/socket.c:1891 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x61/0xcb Freed by task 9: kasan_save_stack mm/kasan/common.c:38 [inline] kasan_set_track+0x4a/0x70 mm/kasan/common.c:45 kasan_set_free_info+0x23/0x40 mm/kasan/generic.c:370 ____kasan_slab_free+0x125/0x160 mm/kasan/common.c:362 __kasan_slab_free+0x11/0x20 mm/kasan/common.c:370 kasan_slab_free include/linux/kasan.h:220 [inline] slab_free_hook mm/slub.c:1600 [inline] slab_free_freelist_hook+0xc5/0x190 mm/slub.c:1626 slab_free mm/slub.c:3208 [inline] kfree+0xc0/0x270 mm/slub.c:4196 l2tp_session_free net/l2tp/l2tp_core.c:168 [inline] l2tp_session_put+0xb2/0x1a0 net/l2tp/l2tp_core.c:193 l2tp_session_delete+0x3a9/0x4a0 net/l2tp/l2tp_core.c:1589 l2tp_tunnel_closeall net/l2tp/l2tp_core.c:1235 [inline] l2tp_tunnel_del_work+0x180/0x3d0 net/l2tp/l2tp_core.c:1273 process_one_work+0x6fd/0xbc0 kernel/workqueue.c:2301 worker_thread+0xa8e/0x13c0 kernel/workqueue.c:2447 kthread+0x324/0x3b0 kernel/kthread.c:313 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298 Last potentially related work creation: kasan_save_stack+0x3a/0x60 mm/kasan/common.c:38 __kasan_record_aux_stack+0xd2/0x100 mm/kasan/generic.c:348 kasan_record_aux_stack_noalloc+0xb/0x10 mm/kasan/generic.c:358 __call_rcu kernel/rcu/tree.c:2980 [inline] call_rcu+0x11a/0x1090 kernel/rcu/tree.c:3054 pppol2tp_release+0x1e3/0x2b0 net/l2tp/l2tp_ppp.c:447 __sock_release net/socket.c:597 [inline] sock_close+0xb8/0x200 net/socket.c:1287 __fput+0x2dc/0x730 fs/file_table.c:281 ____fput+0x15/0x20 fs/file_table.c:314 task_work_run+0x127/0x190 kernel/task_work.c:189 tracehook_notify_resume include/linux/tracehook.h:188 [inline] exit_to_user_mode_loop+0xcb/0xe0 kernel/entry/common.c:172 exit_to_user_mode_prepare+0x76/0xa0 kernel/entry/common.c:199 syscall_exit_to_user_mode+0x1d/0x40 kernel/entry/common.c:274 do_syscall_64+0x3d/0x40 arch/x86/entry/common.c:56 entry_SYSCALL_64_after_hwframe+0x61/0xcb Second to last potentially related work creation: kasan_save_stack+0x3a/0x60 mm/kasan/common.c:38 __kasan_record_aux_stack+0xd2/0x100 mm/kasan/generic.c:348 kasan_record_aux_stack_noalloc+0xb/0x10 mm/kasan/generic.c:358 __call_rcu kernel/rcu/tree.c:2980 [inline] call_rcu+0x11a/0x1090 kernel/rcu/tree.c:3054 fib6_info_release include/net/ip6_fib.h:346 [inline] fib6_del_route net/ipv6/ip6_fib.c:1996 [inline] fib6_del+0xbf0/0xf00 net/ipv6/ip6_fib.c:2029 fib6_clean_node+0x2a1/0x540 net/ipv6/ip6_fib.c:2191 fib6_walk_continue+0x54b/0x740 net/ipv6/ip6_fib.c:2113 fib6_walk+0x153/0x290 net/ipv6/ip6_fib.c:2161 fib6_clean_tree net/ipv6/ip6_fib.c:2241 [inline] __fib6_clean_all net/ipv6/ip6_fib.c:2257 [inline] fib6_clean_all+0x1a1/0x270 net/ipv6/ip6_fib.c:2268 rt6_sync_down_dev net/ipv6/route.c:4793 [inline] rt6_disable_ip+0x114/0x690 net/ipv6/route.c:4798 addrconf_ifdown+0x144/0x1890 net/ipv6/addrconf.c:3787 addrconf_notify+0x3bd/0xea0 net/ipv6/addrconf.c:-1 notifier_call_chain kernel/notifier.c:83 [inline] raw_notifier_call_chain+0x90/0x100 kernel/notifier.c:410 call_netdevice_notifiers_info net/core/dev.c:2052 [inline] call_netdevice_notifiers_extack net/core/dev.c:2064 [inline] call_netdevice_notifiers net/core/dev.c:2078 [inline] dev_close_many+0x328/0x4d0 net/core/dev.c:1653 unregister_netdevice_many+0x477/0x19f0 net/core/dev.c:10755 default_device_exit_batch+0x35e/0x3c0 net/core/dev.c:11298 ops_exit_list net/core/net_namespace.c:190 [inline] cleanup_net+0x5fe/0xb80 net/core/net_namespace.c:609 process_one_work+0x6fd/0xbc0 kernel/workqueue.c:2301 worker_thread+0xa8e/0x13c0 kernel/workqueue.c:2447 kthread+0x324/0x3b0 kernel/kthread.c:313 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298 The buggy address belongs to the object at ffff88811ece3800 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 400 bytes inside of 512-byte region [ffff88811ece3800, ffff88811ece3a00) The buggy address belongs to the page: page:ffffea00047b3800 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x11ece0 head:ffffea00047b3800 order:2 compound_mapcount:0 compound_pincount:0 flags: 0x4000000000010200(slab|head) raw: 4000000000010200 dead000000000100 dead000000000122 ffff888100043080 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 0x152a20(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_HARDWALL), pid 745, ts 34479481585, free_ts 34445671596 set_page_owner include/linux/page_owner.h:35 [inline] post_alloc_hook mm/page_alloc.c:2456 [inline] prep_new_page+0x176/0x190 mm/page_alloc.c:2462 get_page_from_freelist+0x225f/0x23f0 mm/page_alloc.c:4254 __alloc_pages_nodemask+0x29a/0x640 mm/page_alloc.c:5384 alloc_slab_page mm/slub.c:-1 [inline] allocate_slab mm/slub.c:1813 [inline] new_slab+0x84/0x3f0 mm/slub.c:1874 new_slab_objects mm/slub.c:2632 [inline] ___slab_alloc+0x2f8/0x4c0 mm/slub.c:2796 __slab_alloc+0x63/0xa0 mm/slub.c:2836 slab_alloc_node mm/slub.c:2918 [inline] slab_alloc mm/slub.c:2960 [inline] __kmalloc+0x1f9/0x330 mm/slub.c:4034 kmalloc include/linux/slab.h:560 [inline] kzalloc include/linux/slab.h:667 [inline] fib6_info_alloc+0x34/0xe0 net/ipv6/ip6_fib.c:154 ip6_route_info_create+0x4c7/0x1450 net/ipv6/route.c:3671 addrconf_f6i_alloc+0x19c/0x3f0 net/ipv6/route.c:4470 fixup_permanent_addr net/ipv6/addrconf.c:3503 [inline] addrconf_permanent_addr+0x237/0x940 net/ipv6/addrconf.c:3542 addrconf_notify+0x752/0xea0 net/ipv6/addrconf.c:3610 notifier_call_chain kernel/notifier.c:83 [inline] raw_notifier_call_chain+0x90/0x100 kernel/notifier.c:410 call_netdevice_notifiers_info net/core/dev.c:2052 [inline] call_netdevice_notifiers_extack net/core/dev.c:2064 [inline] call_netdevice_notifiers net/core/dev.c:2078 [inline] __dev_notify_flags+0x2f4/0x5b0 net/core/dev.c:8583 dev_change_flags+0xe3/0x1a0 net/core/dev.c:8621 do_setlink+0xb19/0x29a0 net/core/rtnetlink.c:2744 page last free stack trace: reset_page_owner include/linux/page_owner.h:28 [inline] free_pages_prepare mm/page_alloc.c:1349 [inline] __free_pages_ok+0x80b/0x830 mm/page_alloc.c:1629 free_the_page mm/page_alloc.c:5445 [inline] __free_pages+0xd8/0x390 mm/page_alloc.c:5454 __free_slab+0xcf/0x190 mm/slub.c:1899 free_slab mm/slub.c:1914 [inline] discard_slab mm/slub.c:1920 [inline] unfreeze_partials+0x150/0x180 mm/slub.c:2415 put_cpu_partial+0xc1/0x180 mm/slub.c:2451 __slab_free+0x2c9/0x3a0 mm/slub.c:3100 do_slab_free mm/slub.c:3196 [inline] ___cache_free+0x10e/0x130 mm/slub.c:3215 qlink_free+0x50/0x90 mm/kasan/quarantine.c:157 qlist_free_all+0x5f/0xb0 mm/kasan/quarantine.c:176 kasan_quarantine_reduce+0x14a/0x160 mm/kasan/quarantine.c:283 __kasan_slab_alloc+0x2f/0xe0 mm/kasan/common.c:440 kasan_slab_alloc include/linux/kasan.h:244 [inline] slab_post_alloc_hook+0x5d/0x2f0 mm/slab.h:580 slab_alloc_node mm/slub.c:2952 [inline] slab_alloc mm/slub.c:2960 [inline] kmem_cache_alloc+0x15a/0x2d0 mm/slub.c:2965 getname_flags+0xba/0x510 fs/namei.c:141 getname fs/namei.c:212 [inline] __do_sys_rename fs/namei.c:4678 [inline] __se_sys_rename fs/namei.c:4676 [inline] __x64_sys_rename+0x5f/0x90 fs/namei.c:4676 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46 Memory state around the buggy address: ffff88811ece3880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88811ece3900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff88811ece3980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff88811ece3a00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff88811ece3a80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ================================================================== ip6_tunnel: ip6tnl2 xmit: Local address not yet configured! ---------------- Code disassembly (best guess): 0: 89 fb mov %edi,%ebx 2: e8 13 00 00 00 call 0x1a 7: 48 8b 3d ec ca 5e 05 mov 0x55ecaec(%rip),%rdi # 0x55ecafa e: 48 89 de mov %rbx,%rsi 11: e8 c4 d6 39 00 call 0x39d6da 16: 5b pop %rbx 17: 5d pop %rbp 18: c3 ret 19: 00 55 48 add %dl,0x48(%rbp) 1c: 89 e5 mov %esp,%ebp 1e: 48 8b 45 08 mov 0x8(%rbp),%rax 22: 65 48 8b 0d 90 c7 9d mov %gs:0x7e9dc790(%rip),%rcx # 0x7e9dc7ba 29: 7e * 2a: 65 8b 15 95 c7 9d 7e mov %gs:0x7e9dc795(%rip),%edx # 0x7e9dc7c6 <-- trapping instruction 31: f7 c2 00 01 ff 00 test $0xff0100,%edx 37: 74 11 je 0x4a 39: f7 c2 00 01 00 00 test $0x100,%edx 3f: 74 .byte 0x74