================================================================== BUG: KASAN: use-after-free in rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75 Read of size 8 at addr ffff88810f977990 by task syz.2.4289/16231 CPU: 0 PID: 16231 Comm: syz.2.4289 Tainted: G W 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:kasan_check_range+0x1c8/0x2a0 mm/kasan/generic.c:-1 Code: 49 8d 5c 24 07 4d 85 e4 49 0f 49 dc 48 83 e3 f8 49 29 dc 74 0e 41 80 3b 00 75 6b 49 ff c3 49 ff cc 75 f2 5b 41 5c 41 5d 41 5e <41> 5f 5d c3 45 84 ff 0f 85 91 00 00 00 41 f7 c7 00 ff 00 00 0f 85 RSP: 0018:ffffc900010066e0 EFLAGS: 00000246 RAX: ffff888145470001 RBX: 0000000000001000 RCX: ffffffff81d8251d RDX: 0000000000000001 RSI: 0000000000001000 RDI: ffff888145470000 RBP: ffffc900010066e8 R08: ffff888145470fff R09: 1ffff11028a8e1ff R10: dffffc0000000000 R11: ffffed1028a8e200 R12: 0000000000000000 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 memset+0x23/0x40 mm/kasan/shadow.c:44 zero_user_segments include/linux/highmem.h:285 [inline] zero_user_segment include/linux/highmem.h:297 [inline] ext4_mpage_readpages+0x10ad/0x20a0 fs/ext4/readpage.c:379 ext4_readahead+0xe4/0x110 fs/ext4/inode.c:3354 read_pages+0x17b/0xb50 mm/readahead.c:140 page_cache_ra_unbounded+0x638/0x790 mm/readahead.c:248 do_page_cache_ra mm/readahead.c:277 [inline] ondemand_readahead+0x780/0xbc0 mm/readahead.c:559 page_cache_async_ra+0x29f/0x2d0 mm/readahead.c:617 page_cache_async_readahead include/linux/pagemap.h:860 [inline] do_async_mmap_readahead mm/filemap.c:2695 [inline] filemap_fault+0x9c8/0x2020 mm/filemap.c:2805 ext4_filemap_fault+0x8a/0xa0 fs/ext4/inode.c:6431 __do_fault mm/memory.c:4064 [inline] do_read_fault mm/memory.c:4408 [inline] do_fault mm/memory.c:4536 [inline] handle_pte_fault+0x2466/0x3910 mm/memory.c:4800 __handle_mm_fault mm/memory.c:4953 [inline] handle_mm_fault+0xf86/0x1720 mm/memory.c:5367 faultin_page mm/gup.c:902 [inline] __get_user_pages+0xbf8/0x1400 mm/gup.c:1121 __get_user_pages_locked mm/gup.c:1307 [inline] get_dump_page+0x153/0x5c0 mm/gup.c:1586 dump_user_range+0x3c/0x1a0 fs/coredump.c:904 elf_core_dump+0x27af/0x2c20 fs/binfmt_elf.c:2290 do_coredump+0x1be6/0x2910 fs/coredump.c:817 get_signal+0xf4c/0x1300 kernel/signal.c:2788 arch_do_signal_or_restart+0xe7/0x11b0 arch/x86/kernel/signal.c:805 handle_signal_work kernel/entry/common.c:145 [inline] exit_to_user_mode_loop+0xa2/0xe0 kernel/entry/common.c:169 exit_to_user_mode_prepare+0x76/0xa0 kernel/entry/common.c:199 irqentry_exit_to_user_mode+0x9/0x10 kernel/entry/common.c:287 irqentry_exit+0x12/0x60 kernel/entry/common.c:375 exc_page_fault+0x67/0xc0 arch/x86/mm/fault.c:1495 asm_exc_page_fault+0x1e/0x30 arch/x86/include/asm/idtentry.h:571 RIP: 0033:0x7f60a3d9ebd7 Code: e8 fe f9 ff ff 89 f2 48 8d 3d 8d 4f 1b 00 48 8d 35 0a 0b 1e 00 31 c0 e8 37 f8 ff ff 0f 1f 80 00 00 00 00 53 89 fb 48 83 ec 10 <64> 8b 04 25 a4 ff ff ff 85 c0 74 2a 89 fe 31 c0 bf 3c 00 00 00 e8 RSP: 002b:00007f60a2902120 EFLAGS: 00010202 RAX: 0000000000000000 RBX: 000000000000000b RCX: 00007f60a3ee9159 RDX: 00007f60a2902140 RSI: 00007f60a2902270 RDI: 000000000000000b RBP: 00007f60a3f8006b R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000 R13: 00007f60a4171128 R14: 00007f60a4171090 R15: 00007fff166afc88 Allocated by task 16285: 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 11959: 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 inetdev_destroy net/ipv4/devinet.c:330 [inline] inetdev_event+0x825/0x1010 net/ipv4/devinet.c:1612 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] unregister_netdevice_many+0x100e/0x19f0 net/core/dev.c:10778 ip_tunnel_delete_nets+0x343/0x390 net/ipv4/ip_tunnel.c:1122 vti_exit_batch_net+0x22/0x30 net/ipv4/ip_vti.c:512 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 ffff88810f977800 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 400 bytes inside of 512-byte region [ffff88810f977800, ffff88810f977a00) The buggy address belongs to the page: page:ffffea00043e5d00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x10f974 head:ffffea00043e5d00 order:2 compound_mapcount:0 compound_pincount:0 flags: 0x4000000000010200(slab|head) raw: 4000000000010200 0000000000000000 0000000100000001 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 53, ts 26353209928, free_ts 26352274021 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] neigh_alloc net/core/neighbour.c:439 [inline] ___neigh_create+0x6ec/0x1a70 net/core/neighbour.c:592 __neigh_create+0x31/0x40 net/core/neighbour.c:680 ip6_finish_output2+0x8fe/0x1540 net/ipv6/ip6_output.c:129 __ip6_finish_output+0x5fd/0x790 net/ipv6/ip6_output.c:203 ip6_finish_output+0x33/0x1e0 net/ipv6/ip6_output.c:213 NF_HOOK_COND include/linux/netfilter.h:288 [inline] ip6_output+0x1fa/0x420 net/ipv6/ip6_output.c:236 dst_output include/net/dst.h:451 [inline] NF_HOOK include/linux/netfilter.h:299 [inline] ndisc_send_skb+0x721/0xbc0 net/ipv6/ndisc.c:513 ndisc_send_rs+0x711/0x960 net/ipv6/ndisc.c:707 addrconf_dad_completed+0x945/0xe30 net/ipv6/addrconf.c:4293 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_kmalloc_large+0x1a/0xb0 mm/kasan/common.c:529 kasan_kmalloc_large include/linux/kasan.h:264 [inline] kmalloc_order+0x112/0x160 mm/slab_common.c:849 kmalloc_order_trace+0x16/0x80 mm/slab_common.c:859 kmalloc_large include/linux/slab.h:484 [inline] __kmalloc+0x1e6/0x330 mm/slub.c:4027 __kmalloc_node include/linux/slab.h:421 [inline] kmalloc_node include/linux/slab.h:578 [inline] kvmalloc_node+0x88/0x130 mm/util.c:612 kvmalloc include/linux/mm.h:833 [inline] kvmalloc_array include/linux/mm.h:851 [inline] kvcalloc include/linux/mm.h:856 [inline] btf_add_type kernel/bpf/btf.c:1410 [inline] btf_check_all_metas+0x343/0x820 kernel/bpf/btf.c:3814 Memory state around the buggy address: ffff88810f977880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88810f977900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff88810f977980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff88810f977a00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff88810f977a80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ================================================================== ---------------- Code disassembly (best guess): 0: 49 8d 5c 24 07 lea 0x7(%r12),%rbx 5: 4d 85 e4 test %r12,%r12 8: 49 0f 49 dc cmovns %r12,%rbx c: 48 83 e3 f8 and $0xfffffffffffffff8,%rbx 10: 49 29 dc sub %rbx,%r12 13: 74 0e je 0x23 15: 41 80 3b 00 cmpb $0x0,(%r11) 19: 75 6b jne 0x86 1b: 49 ff c3 inc %r11 1e: 49 ff cc dec %r12 21: 75 f2 jne 0x15 23: 5b pop %rbx 24: 41 5c pop %r12 26: 41 5d pop %r13 28: 41 5e pop %r14 * 2a: 41 5f pop %r15 <-- trapping instruction 2c: 5d pop %rbp 2d: c3 ret 2e: 45 84 ff test %r15b,%r15b 31: 0f 85 91 00 00 00 jne 0xc8 37: 41 f7 c7 00 ff 00 00 test $0xff00,%r15d 3e: 0f .byte 0xf 3f: 85 .byte 0x85