================================================================== BUG: KASAN: use-after-free in rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75 Read of size 8 at addr ffff88812b4d1990 by task syz.7.1179/4454 CPU: 1 PID: 4454 Comm: syz.7.1179 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:__pvclock_read_cycles arch/x86/include/asm/pvclock.h:-1 [inline] RIP: 0010:pvclock_clocksource_read+0x1c2/0x660 arch/x86/kernel/pvclock.c:76 Code: 85 60 ff ff ff 42 0f b6 04 20 84 c0 0f 85 69 02 00 00 48 8b 85 68 ff ff ff 42 0f b6 04 20 84 c0 48 8b 55 98 0f 85 9f 02 00 00 <48> 8b 45 90 4c 8b 28 48 8b 85 70 ff ff ff 42 0f b6 04 20 84 c0 0f RSP: 0018:ffffc90000bd7a60 EFLAGS: 00000246 RAX: 0000000000000000 RBX: 0000000000000004 RCX: 00000000000000ff RDX: 1ffffffff0dcf408 RSI: 0000003af1c636c7 RDI: ffffffff86e7a040 RBP: ffffc90000bd7b30 R08: ffffffff86e7a048 R09: ffffffff86e7a058 R10: ffffffff86e7a05c R11: ffffffff86e7a043 R12: dffffc0000000000 R13: 0000000000000000 R14: 1ffffffff0dcf408 R15: 00000000e8ba357a kvm_clock_read arch/x86/kernel/kvmclock.c:80 [inline] kvm_sched_clock_read+0x18/0x40 arch/x86/kernel/kvmclock.c:92 paravirt_sched_clock arch/x86/include/asm/paravirt.h:22 [inline] sched_clock+0x3a/0x40 arch/x86/kernel/tsc.c:252 bpf_test_run+0x5a9/0x9c0 net/bpf/test_run.c:116 bpf_prog_test_run_skb+0xa10/0x1160 net/bpf/test_run.c:644 bpf_prog_test_run+0x34a/0x3c0 kernel/bpf/syscall.c:3156 __do_sys_bpf kernel/bpf/syscall.c:4453 [inline] __se_sys_bpf+0x501/0x740 kernel/bpf/syscall.c:4391 __x64_sys_bpf+0x7b/0x90 kernel/bpf/syscall.c:4391 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x61/0xcb RIP: 0033:0x7f88492e5159 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:00007f8847d3e028 EFLAGS: 00000246 ORIG_RAX: 0000000000000141 RAX: ffffffffffffffda RBX: 00007f884956cfa0 RCX: 00007f88492e5159 RDX: 0000000000000050 RSI: 0000200000000300 RDI: 000000000000000a RBP: 00007f884937c06b R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f884956d038 R14: 00007f884956cfa0 R15: 00007fff3f91de88 Allocated by task 4485: 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 409: 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] aca_free_rcu+0x89/0xe0 net/ipv6/anycast.c:249 rcu_do_batch+0x488/0xaf0 kernel/rcu/tree.c:2494 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 The buggy address belongs to the object at ffff88812b4d1800 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 400 bytes inside of 512-byte region [ffff88812b4d1800, ffff88812b4d1a00) The buggy address belongs to the page: page:ffffea0004ad3400 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x12b4d0 head:ffffea0004ad3400 order:2 compound_mapcount:0 compound_pincount:0 flags: 0x4000000000010200(slab|head) raw: 4000000000010200 ffffea0004a78c00 0000000400000004 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 0x1d2a20(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 301, ts 30446937167, free_ts 25043932789 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] ndisc_alloc_skb net/ipv6/ndisc.c:422 [inline] ndisc_send_ns+0x347/0xb10 net/ipv6/ndisc.c:631 addrconf_dad_work+0xa40/0x1480 net/ipv6/addrconf.c:4216 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 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_pcp_prepare mm/page_alloc.c:1421 [inline] free_unref_page_prepare+0x2b7/0x2d0 mm/page_alloc.c:3336 free_unref_page mm/page_alloc.c:3391 [inline] free_the_page mm/page_alloc.c:5443 [inline] __free_pages+0x146/0x390 mm/page_alloc.c:5454 __vunmap+0x801/0x980 mm/vmalloc.c:2307 __vfree mm/vmalloc.c:2356 [inline] vfree+0x61/0x90 mm/vmalloc.c:2387 kvfree+0x26/0x40 mm/util.c:645 translate_table+0x117d/0x1f60 net/ipv4/netfilter/ip_tables.c:735 do_replace net/ipv4/netfilter/ip_tables.c:1136 [inline] do_ipt_set_ctl+0x957/0xd70 net/ipv4/netfilter/ip_tables.c:1633 nf_setsockopt+0x272/0x2a0 net/netfilter/nf_sockopt.c:101 ip_setsockopt+0x29f2/0x35b0 net/ipv4/ip_sockglue.c:1442 udp_setsockopt+0x8a/0xa0 net/ipv4/udp.c:2750 sock_common_setsockopt+0xa0/0xb0 net/core/sock.c:3326 __sys_setsockopt+0x2fa/0x480 net/socket.c:2147 __do_sys_setsockopt net/socket.c:2158 [inline] __se_sys_setsockopt net/socket.c:2155 [inline] __x64_sys_setsockopt+0xbf/0xd0 net/socket.c:2155 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x61/0xcb Memory state around the buggy address: ffff88812b4d1880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88812b4d1900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff88812b4d1980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff88812b4d1a00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff88812b4d1a80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ================================================================== ---------------- Code disassembly (best guess), 4 bytes skipped: 0: ff 42 0f incl 0xf(%rdx) 3: b6 04 mov $0x4,%dh 5: 20 84 c0 0f 85 69 02 and %al,0x269850f(%rax,%rax,8) c: 00 00 add %al,(%rax) e: 48 8b 85 68 ff ff ff mov -0x98(%rbp),%rax 15: 42 0f b6 04 20 movzbl (%rax,%r12,1),%eax 1a: 84 c0 test %al,%al 1c: 48 8b 55 98 mov -0x68(%rbp),%rdx 20: 0f 85 9f 02 00 00 jne 0x2c5 * 26: 48 8b 45 90 mov -0x70(%rbp),%rax <-- trapping instruction 2a: 4c 8b 28 mov (%rax),%r13 2d: 48 8b 85 70 ff ff ff mov -0x90(%rbp),%rax 34: 42 0f b6 04 20 movzbl (%rax,%r12,1),%eax 39: 84 c0 test %al,%al 3b: 0f .byte 0xf