================================================================== BUG: KASAN: use-after-free in rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75 Read of size 8 at addr ffff888116127990 by task udevd/304 CPU: 0 PID: 304 Comm: udevd Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026 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:write_comp_data kernel/kcov.c:218 [inline] RIP: 0010:__sanitizer_cov_trace_switch+0x64/0xe0 kernel/kcov.c:320 Code: 41 57 41 56 41 54 53 48 8d 4c 09 01 48 8b 55 08 65 4c 8b 05 6e c6 9d 7e 45 31 c9 eb 08 49 ff c1 4c 39 c8 74 77 4e 8b 54 ce 10 <65> 44 8b 1d 60 c6 9d 7e 41 f7 c3 00 01 ff 00 74 13 41 f7 c3 00 01 RSP: 0018:ffffc900079c76f0 EFLAGS: 00000206 RAX: 0000000000000005 RBX: 0000000000000073 RCX: 0000000000000001 RDX: ffffffff825ba4dd RSI: ffffffff86771d60 RDI: 0000000000000073 RBP: ffffc900079c7710 R08: ffff88812630bb40 R09: 0000000000000002 R10: 000000000000006c R11: 0000000000000000 R12: ffffffff854c7b09 R13: 0000000000000073 R14: 0000000000000073 R15: 0000000000000073 format_decode+0x6ed/0x1520 lib/vsprintf.c:2484 vsnprintf+0xea/0x1990 lib/vsprintf.c:2641 add_uevent_var+0x1d5/0x450 lib/kobject_uevent.c:680 dev_uevent+0x17d/0x520 drivers/base/core.c:2214 uevent_show+0x1b2/0x340 drivers/base/core.c:2302 dev_attr_show+0x56/0xd0 drivers/base/core.c:2002 sysfs_kf_seq_show+0x266/0x3d0 fs/sysfs/file.c:61 kernfs_seq_show+0x119/0x160 fs/kernfs/file.c:168 seq_read_iter+0x472/0xce0 fs/seq_file.c:230 kernfs_fop_read_iter+0x146/0x460 fs/kernfs/file.c:241 call_read_iter include/linux/fs.h:2060 [inline] new_sync_read fs/read_write.c:415 [inline] vfs_read+0x62a/0xa50 fs/read_write.c:496 ksys_read+0x14a/0x260 fs/read_write.c:634 __do_sys_read fs/read_write.c:644 [inline] __se_sys_read fs/read_write.c:642 [inline] __x64_sys_read+0x7b/0x90 fs/read_write.c:642 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x61/0xcb RIP: 0033:0x7f2fcdb86407 Code: 48 89 fa 4c 89 df e8 38 aa 00 00 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 1a 5b c3 0f 1f 84 00 00 00 00 00 48 8b 44 24 10 0f 05 <5b> c3 0f 1f 80 00 00 00 00 83 e2 39 83 fa 08 75 de e8 23 ff ff ff RSP: 002b:00007ffe266c9dc0 EFLAGS: 00000202 ORIG_RAX: 0000000000000000 RAX: ffffffffffffffda RBX: 00007f2fcda98880 RCX: 00007f2fcdb86407 RDX: 0000000000001000 RSI: 000055f480a079a0 RDI: 0000000000000009 RBP: 00007f2fcdcceff0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000202 R12: 000000000000000a R13: 00007f2fcdcceea0 R14: 0000000000000000 R15: 000055f480997b50 Allocated by task 14064: 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:1866 [inline] __sys_connect+0x3ce/0x450 net/socket.c:1883 __do_sys_connect net/socket.c:1893 [inline] __se_sys_connect net/socket.c:1890 [inline] __x64_sys_connect+0x7a/0x90 net/socket.c:1890 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x61/0xcb Freed by task 356: 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:1286 __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 kvfree_call_rcu+0x117/0x670 kernel/rcu/tree.c:3539 inet6_ifa_finish_destroy+0x129/0x1b0 net/ipv6/addrconf.c:1001 in6_ifa_put include/net/addrconf.h:459 [inline] addrconf_ifdown+0x121c/0x1890 net/ipv6/addrconf.c:3924 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:2054 [inline] call_netdevice_notifiers_extack net/core/dev.c:2066 [inline] call_netdevice_notifiers net/core/dev.c:2080 [inline] dev_close_many+0x328/0x4d0 net/core/dev.c:1655 unregister_netdevice_many+0x477/0x19f0 net/core/dev.c:10757 default_device_exit_batch+0x35e/0x3c0 net/core/dev.c:11300 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 ffff888116127800 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 400 bytes inside of 512-byte region [ffff888116127800, ffff888116127a00) The buggy address belongs to the page: page:ffffea0004584900 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff888116126800 pfn:0x116124 head:ffffea0004584900 order:2 compound_mapcount:0 compound_pincount:0 flags: 0x4000000000010200(slab|head) raw: 4000000000010200 ffffea00042f6400 0000000200000002 ffff888100043080 raw: ffff888116126800 000000008010000d 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 99, ts 5840010872, free_ts 0 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:6006 sock_alloc_send_pskb+0x87f/0x9a0 net/core/sock.c:2393 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] sock_write_iter+0x2a6/0x3a0 net/socket.c:1018 call_write_iter include/linux/fs.h:2066 [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 page_owner free stack trace missing Memory state around the buggy address: ffff888116127880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff888116127900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff888116127980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff888116127a00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff888116127a80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ================================================================== ---------------- Code disassembly (best guess): 0: 41 57 push %r15 2: 41 56 push %r14 4: 41 54 push %r12 6: 53 push %rbx 7: 48 8d 4c 09 01 lea 0x1(%rcx,%rcx,1),%rcx c: 48 8b 55 08 mov 0x8(%rbp),%rdx 10: 65 4c 8b 05 6e c6 9d mov %gs:0x7e9dc66e(%rip),%r8 # 0x7e9dc686 17: 7e 18: 45 31 c9 xor %r9d,%r9d 1b: eb 08 jmp 0x25 1d: 49 ff c1 inc %r9 20: 4c 39 c8 cmp %r9,%rax 23: 74 77 je 0x9c 25: 4e 8b 54 ce 10 mov 0x10(%rsi,%r9,8),%r10 * 2a: 65 44 8b 1d 60 c6 9d mov %gs:0x7e9dc660(%rip),%r11d # 0x7e9dc692 <-- trapping instruction 31: 7e 32: 41 f7 c3 00 01 ff 00 test $0xff0100,%r11d 39: 74 13 je 0x4e 3b: 41 rex.B 3c: f7 .byte 0xf7 3d: c3 ret 3e: 00 01 add %al,(%rcx)