================================================================== BUG: KASAN: use-after-free in rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75 Read of size 8 at addr ffff88810d440590 by task syz.6.211/1173 CPU: 1 PID: 1173 Comm: syz.6.211 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:check_region_inline mm/kasan/generic.c:-1 [inline] RIP: 0010:kasan_check_range+0x11/0x2a0 mm/kasan/generic.c:189 Code: 5d c3 0f 0b b8 ea ff ff ff c3 0f 0b b8 ea ff ff ff c3 00 00 cc cc 00 00 cc b0 01 48 85 f6 0f 84 c0 01 00 00 55 48 89 e5 41 57 <41> 56 41 55 41 54 53 49 89 f8 49 01 f0 0f 82 1d 02 00 00 49 89 f8 RSP: 0018:ffffc90000b97738 EFLAGS: 00000202 RAX: 0000000000000001 RBX: ffffea0004d86a88 RCX: ffffffff818aceb9 RDX: 0000000000000001 RSI: 0000000000000004 RDI: ffffea0004d86af4 RBP: ffffc90000b97740 R08: ffffea0004d86ab7 R09: 1ffffd40009b0d56 R10: dffffc0000000000 R11: fffff940009b0d57 R12: 0000000000000006 R13: ffffea0004d86ac0 R14: dffffc0000000000 R15: 0000000000000000 __kasan_check_write+0x14/0x20 mm/kasan/shadow.c:37 instrument_atomic_read_write include/linux/instrumented.h:101 [inline] atomic_dec_and_test include/asm-generic/atomic-instrumented.h:748 [inline] page_ref_dec_and_test include/linux/page_ref.h:148 [inline] put_page_testzero include/linux/mm.h:773 [inline] release_pages+0x1e9/0xe90 mm/swap.c:1066 pagevec_lru_move_fn+0x193/0x210 mm/swap.c:235 __pagevec_lru_add mm/swap.c:1217 [inline] lru_cache_add+0x118/0x380 mm/swap.c:533 shmem_getpage_gfp+0x97d/0x20f0 mm/shmem.c:1957 shmem_getpage mm/shmem.c:161 [inline] shmem_write_begin+0xce/0x1b0 mm/shmem.c:2497 generic_perform_write+0x2ce/0x540 mm/filemap.c:3509 __generic_file_write_iter+0x24b/0x480 mm/filemap.c:3638 generic_file_write_iter+0xa9/0x1d0 mm/filemap.c:3670 call_write_iter include/linux/fs.h:2072 [inline] new_sync_write fs/read_write.c:518 [inline] vfs_write+0x770/0xd70 fs/read_write.c:605 ksys_write+0x14a/0x260 fs/read_write.c:658 __do_sys_write fs/read_write.c:670 [inline] __se_sys_write fs/read_write.c:667 [inline] __x64_sys_write+0x7b/0x90 fs/read_write.c:667 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x61/0xcb RIP: 0033:0x7f0b72977159 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:00007f0b713d0028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00007f0b72bfefa0 RCX: 00007f0b72977159 RDX: 00000000fffffdef RSI: 00002000000000c0 RDI: 0000000000000003 RBP: 00007f0b72a0e06b R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f0b72bff038 R14: 00007f0b72bfefa0 R15: 00007fffb19e8088 Allocated by task 1090: 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 300: 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 get_signal+0x1281/0x1300 kernel/signal.c:2579 arch_do_signal_or_restart+0xe7/0x11b0 arch/x86/kernel/signal.c:805 handle_signal_work kernel/entry/common.c:148 [inline] exit_to_user_mode_loop+0xa2/0xe0 kernel/entry/common.c:172 exit_to_user_mode_prepare+0x76/0xa0 kernel/entry/common.c:202 syscall_exit_to_user_mode+0x1d/0x40 kernel/entry/common.c:277 do_syscall_64+0x3d/0x40 arch/x86/entry/common.c:56 entry_SYSCALL_64_after_hwframe+0x61/0xcb The buggy address belongs to the object at ffff88810d440400 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 400 bytes inside of 512-byte region [ffff88810d440400, ffff88810d440600) The buggy address belongs to the page: page:ffffea0004351000 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x10d440 head:ffffea0004351000 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 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 83, ts 20844590448, free_ts 20780710653 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_track_caller+0x1e4/0x310 mm/slub.c:4541 __kmalloc_reserve net/core/skbuff.c:144 [inline] __alloc_skb+0xdc/0x520 net/core/skbuff.c:212 alloc_skb include/linux/skbuff.h:1126 [inline] alloc_skb_with_frags+0xa3/0x560 net/core/skbuff.c:6048 sock_alloc_send_pskb+0x87f/0x9a0 net/core/sock.c:2392 unix_dgram_sendmsg+0x6f3/0x18f0 net/unix/af_unix.c:1725 sock_sendmsg_nosec net/socket.c:652 [inline] __sock_sendmsg net/socket.c:664 [inline] __sys_sendto+0x467/0x620 net/socket.c:2007 __do_sys_sendto net/socket.c:2019 [inline] __se_sys_sendto net/socket.c:2015 [inline] __x64_sys_sendto+0xe5/0x100 net/socket.c:2015 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x61/0xcb 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_trace+0x155/0x2e0 mm/slub.c:2977 kmalloc include/linux/slab.h:555 [inline] syslog_print+0x127/0x720 kernel/printk/printk.c:1487 do_syslog+0x94c/0x9a0 kernel/printk/printk.c:1644 __do_sys_syslog kernel/printk/printk.c:1736 [inline] __se_sys_syslog kernel/printk/printk.c:1734 [inline] __x64_sys_syslog+0x7c/0x90 kernel/printk/printk.c:1734 Memory state around the buggy address: ffff88810d440480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88810d440500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff88810d440580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff88810d440600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff88810d440680: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ================================================================== ip6_tunnel: ip6tnl1 xmit: Local address not yet configured! ---------------- Code disassembly (best guess): 0: 5d pop %rbp 1: c3 ret 2: 0f 0b ud2 4: b8 ea ff ff ff mov $0xffffffea,%eax 9: c3 ret a: 0f 0b ud2 c: b8 ea ff ff ff mov $0xffffffea,%eax 11: c3 ret 12: 00 00 add %al,(%rax) 14: cc int3 15: cc int3 16: 00 00 add %al,(%rax) 18: cc int3 19: b0 01 mov $0x1,%al 1b: 48 85 f6 test %rsi,%rsi 1e: 0f 84 c0 01 00 00 je 0x1e4 24: 55 push %rbp 25: 48 89 e5 mov %rsp,%rbp 28: 41 57 push %r15 * 2a: 41 56 push %r14 <-- trapping instruction 2c: 41 55 push %r13 2e: 41 54 push %r12 30: 53 push %rbx 31: 49 89 f8 mov %rdi,%r8 34: 49 01 f0 add %rsi,%r8 37: 0f 82 1d 02 00 00 jb 0x25a 3d: 49 89 f8 mov %rdi,%r8