================================================================== BUG: KASAN: use-after-free in rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75 Read of size 8 at addr ffff88812f67e590 by task syz.3.87/719 CPU: 0 PID: 719 Comm: syz.3.87 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/07/2026 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:__set_page_owner_handle mm/page_owner.c:197 [inline] RIP: 0010:__set_page_owner+0xbd/0x2a0 mm/page_owner.c:220 Code: c7 c0 a0 97 64 86 48 c1 e8 03 48 89 45 b8 44 89 65 c8 48 8b 1d e4 85 c0 04 49 8d 7c 1f 08 48 89 f8 48 c1 e8 03 42 0f b6 04 28 <84> c0 0f 85 18 01 00 00 4c 01 fb 8b 45 c4 89 43 08 48 89 d8 48 c1 RSP: 0018:ffffc90000e56d98 EFLAGS: 00000a02 RAX: 0000000000000000 RBX: 0000000000000008 RCX: 0000000000000000 RDX: ffff88810d73d000 RSI: 0000000000000000 RDI: ffff8881042a5190 RBP: ffffc90000e56de8 R08: 0000000000000010 R09: ffffffff84a000c5 R10: 0000000000000002 R11: 000000009030c0c7 R12: 0000000000100cca R13: dffffc0000000000 R14: 0000000000000000 R15: ffff8881042a5180 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_pages include/linux/gfp.h:544 [inline] __alloc_pages_node include/linux/gfp.h:557 [inline] alloc_pages_node include/linux/gfp.h:571 [inline] alloc_pages include/linux/gfp.h:590 [inline] shmem_alloc_page+0x1fd/0x380 mm/shmem.c:1580 shmem_alloc_and_acct_page+0x3d3/0x840 mm/shmem.c:1605 shmem_getpage_gfp+0x785/0x20f0 mm/shmem.c:1918 shmem_fault+0x2b5/0x650 mm/shmem.c:2139 __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 populate_vma_page_range mm/gup.c:1454 [inline] __mm_populate+0x31c/0x420 mm/gup.c:1502 mm_populate include/linux/mm.h:2793 [inline] vm_mmap_pgoff+0x23b/0x350 mm/util.c:548 ksys_mmap_pgoff+0xfd/0x1e0 mm/mmap.c:1712 __do_sys_mmap arch/x86/kernel/sys_x86_64.c:95 [inline] __se_sys_mmap arch/x86/kernel/sys_x86_64.c:86 [inline] __x64_sys_mmap+0xfa/0x110 arch/x86/kernel/sys_x86_64.c:86 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x61/0xcb RIP: 0033:0x7f0e7613db19 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:00007f0e74b95028 EFLAGS: 00000246 ORIG_RAX: 0000000000000009 RAX: ffffffffffffffda RBX: 00007f0e763c3fa0 RCX: 00007f0e7613db19 RDX: b635773f06ebbeee RSI: 0000000000b36000 RDI: 0000200000000000 RBP: 00007f0e761d5b70 R08: ffffffffffffffff R09: 0000000000000000 R10: 0000000000008031 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f0e763c4038 R14: 00007f0e763c3fa0 R15: 00007ffcde0e3158 Allocated by task 715: 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:175 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 ffff88812f67e400 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 400 bytes inside of 512-byte region [ffff88812f67e400, ffff88812f67e600) The buggy address belongs to the page: page:ffffea0004bd9f00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x12f67c head:ffffea0004bd9f00 order:2 compound_mapcount:0 compound_pincount:0 flags: 0x4000000000010200(slab|head) raw: 4000000000010200 0000000000000000 0000000100000001 ffff888100043080 raw: 0000000000000000 0000000080100010 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 15, ts 22570777301, free_ts 21684745348 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_ns+0x879/0xb10 net/ipv6/ndisc.c:655 addrconf_dad_work+0xa40/0x1480 net/ipv6/addrconf.c:4224 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_list+0x129/0x9c0 mm/page_alloc.c:3443 release_pages+0xe41/0xe90 mm/swap.c:1103 __pagevec_release+0x71/0xe0 mm/swap.c:1123 pagevec_release include/linux/pagevec.h:88 [inline] shmem_undo_range+0x741/0x1740 mm/shmem.c:965 shmem_truncate_range mm/shmem.c:1069 [inline] shmem_evict_inode+0x1dc/0x970 mm/shmem.c:1169 evict+0x4a9/0x940 fs/inode.c:612 iput_final fs/inode.c:1736 [inline] iput+0x654/0x7e0 fs/inode.c:1762 dentry_unlink_inode+0x2d5/0x390 fs/dcache.c:378 __dentry_kill+0x45b/0x660 fs/dcache.c:583 dentry_kill+0xc0/0x2a0 fs/dcache.c:-1 dput+0x42/0x80 fs/dcache.c:883 __fput+0x4bd/0x730 fs/file_table.c:294 ____fput+0x15/0x20 fs/file_table.c:314 task_work_run+0x127/0x190 kernel/task_work.c:189 exit_task_work include/linux/task_work.h:33 [inline] do_exit+0xa7c/0x24e0 kernel/exit.c:879 Memory state around the buggy address: ffff88812f67e480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88812f67e500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff88812f67e580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff88812f67e600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff88812f67e680: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ================================================================== ---------------- Code disassembly (best guess): 0: c7 c0 a0 97 64 86 mov $0x866497a0,%eax 6: 48 c1 e8 03 shr $0x3,%rax a: 48 89 45 b8 mov %rax,-0x48(%rbp) e: 44 89 65 c8 mov %r12d,-0x38(%rbp) 12: 48 8b 1d e4 85 c0 04 mov 0x4c085e4(%rip),%rbx # 0x4c085fd 19: 49 8d 7c 1f 08 lea 0x8(%r15,%rbx,1),%rdi 1e: 48 89 f8 mov %rdi,%rax 21: 48 c1 e8 03 shr $0x3,%rax 25: 42 0f b6 04 28 movzbl (%rax,%r13,1),%eax * 2a: 84 c0 test %al,%al <-- trapping instruction 2c: 0f 85 18 01 00 00 jne 0x14a 32: 4c 01 fb add %r15,%rbx 35: 8b 45 c4 mov -0x3c(%rbp),%eax 38: 89 43 08 mov %eax,0x8(%rbx) 3b: 48 89 d8 mov %rbx,%rax 3e: 48 rex.W 3f: c1 .byte 0xc1