================================================================== BUG: KASAN: use-after-free in rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75 Read of size 8 at addr ffff88811e200590 by task syz-executor/290 CPU: 0 PID: 290 Comm: syz-executor Tainted: G W 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:88 dump_stack_lvl+0x110/0x170 lib/dump_stack.c:106 print_address_description+0x71/0x200 mm/kasan/report.c:316 print_report+0x4a/0x60 mm/kasan/report.c:420 kasan_report+0x122/0x150 mm/kasan/report.c:524 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report_generic.c:351 rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75 rcu_do_batch+0x40d/0xc30 kernel/rcu/tree.c:2283 rcu_core+0x486/0xf00 kernel/rcu/tree.c:2557 rcu_core_si+0x9/0x10 kernel/rcu/tree.c:2574 handle_softirqs+0x1dd/0x5f0 kernel/softirq.c:642 __do_softirq kernel/softirq.c:680 [inline] invoke_softirq kernel/softirq.c:497 [inline] __irq_exit_rcu+0x52/0xf0 kernel/softirq.c:729 irq_exit_rcu+0x9/0x10 kernel/softirq.c:741 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1118 [inline] sysvec_apic_timer_interrupt+0xa9/0xc0 arch/x86/kernel/apic/apic.c:1118 asm_sysvec_apic_timer_interrupt+0x1b/0x20 arch/x86/include/asm/idtentry.h:691 RIP: 0010:memory_is_nonzero mm/kasan/generic.c:101 [inline] RIP: 0010:memory_is_poisoned_n mm/kasan/generic.c:128 [inline] RIP: 0010:memory_is_poisoned mm/kasan/generic.c:159 [inline] RIP: 0010:check_region_inline mm/kasan/generic.c:180 [inline] RIP: 0010:kasan_check_range+0x6d/0x2a0 mm/kasan/generic.c:189 Code: 89 fe 49 c1 ee 03 49 ba 00 00 00 00 00 fc ff df 4f 8d 1c 16 4c 8d 44 3e ff 4d 89 c1 49 c1 e9 03 4b 8d 1c 29 49 89 dc 4d 29 dc <49> 83 fc 10 7f 29 4d 85 e4 0f 84 45 01 00 00 4c 89 cb 48 f7 d3 4c RSP: 0018:ffffc9000daff678 EFLAGS: 00000202 RAX: ffffffff81aafc01 RBX: fffff9400097b519 RCX: ffffffff81aafff3 RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffea0004bda8c0 RBP: ffffc9000daff6a0 R08: ffffea0004bda8c7 R09: 1ffffd400097b518 R10: dffffc0000000000 R11: fffff9400097b518 R12: 0000000000000001 R13: dffffc0000000001 R14: 1ffffd400097b518 R15: 00000000100400fb __kasan_check_read+0x11/0x20 mm/kasan/shadow.c:31 instrument_atomic_read include/linux/instrumented.h:72 [inline] _test_bit include/asm-generic/bitops/instrumented-non-atomic.h:141 [inline] PageSwapBacked include/linux/page-flags.h:509 [inline] mm_counter_file include/linux/mm.h:2476 [inline] mm_counter include/linux/mm.h:2485 [inline] copy_present_pte mm/memory.c:-1 [inline] copy_pte_range mm/memory.c:1111 [inline] copy_pmd_range mm/memory.c:1197 [inline] copy_pud_range mm/memory.c:1234 [inline] copy_p4d_range mm/memory.c:1258 [inline] copy_page_range+0x14e3/0x27f0 mm/memory.c:1356 dup_mmap kernel/fork.c:778 [inline] dup_mm kernel/fork.c:1672 [inline] copy_mm+0xf90/0x1ad0 kernel/fork.c:1724 copy_process+0x12d8/0x3500 kernel/fork.c:2487 kernel_clone+0x22f/0x7f0 kernel/fork.c:2903 __do_sys_clone kernel/fork.c:3046 [inline] __se_sys_clone kernel/fork.c:3030 [inline] __x64_sys_clone+0x193/0x200 kernel/fork.c:3030 x64_sys_call+0x990/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:57 do_syscall_x64 arch/x86/entry/common.c:46 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76 entry_SYSCALL_64_after_hwframe+0x68/0xd2 RIP: 0033:0x7f4846bc8592 Code: 89 e7 e8 71 8b f7 ff 45 31 c0 31 d2 31 f6 64 48 8b 04 25 10 00 00 00 bf 11 00 20 01 4c 8d 90 d0 02 00 00 b8 38 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 66 89 c5 85 c0 75 3b 64 48 8b 04 25 10 00 00 RSP: 002b:00007ffc614a2470 EFLAGS: 00000246 ORIG_RAX: 0000000000000038 RAX: ffffffffffffffda RBX: 00007ffc614a2470 RCX: 00007f4846bc8592 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000001200011 RBP: 00007ffc614a25fc R08: 0000000000000000 R09: 0000000000000001 R10: 000055556486e7d0 R11: 0000000000000246 R12: 0000000000000000 R13: 00000000000927c0 R14: 0000000000008dbc R15: 00007ffc614a2650 Allocated by task 839: kasan_save_stack mm/kasan/common.c:46 [inline] kasan_set_track+0x4b/0x70 mm/kasan/common.c:53 kasan_save_alloc_info+0x1f/0x30 mm/kasan/generic.c:505 ____kasan_kmalloc mm/kasan/common.c:380 [inline] __kasan_kmalloc+0x95/0xb0 mm/kasan/common.c:389 kasan_kmalloc include/linux/kasan.h:212 [inline] __do_kmalloc_node mm/slab_common.c:938 [inline] __kmalloc+0xb4/0x1e0 mm/slab_common.c:951 kmalloc include/linux/slab.h:568 [inline] kzalloc include/linux/slab.h:699 [inline] l2tp_session_create+0x38/0xbd0 net/l2tp/l2tp_core.c:1614 pppol2tp_connect+0xbf5/0x1640 net/l2tp/l2tp_ppp.c:771 __sys_connect_file net/socket.c:2001 [inline] __sys_connect+0x3da/0x460 net/socket.c:2018 __do_sys_connect net/socket.c:2028 [inline] __se_sys_connect net/socket.c:2025 [inline] __x64_sys_connect+0x7a/0x90 net/socket.c:2025 x64_sys_call+0x88d/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:43 do_syscall_x64 arch/x86/entry/common.c:46 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76 entry_SYSCALL_64_after_hwframe+0x68/0xd2 Freed by task 308: kasan_save_stack mm/kasan/common.c:46 [inline] kasan_set_track+0x4b/0x70 mm/kasan/common.c:53 kasan_save_free_info+0x2b/0x40 mm/kasan/generic.c:516 ____kasan_slab_free+0x132/0x180 mm/kasan/common.c:242 __kasan_slab_free+0x11/0x20 mm/kasan/common.c:250 kasan_slab_free include/linux/kasan.h:178 [inline] slab_free_hook mm/slub.c:1750 [inline] slab_free_freelist_hook+0xc2/0x190 mm/slub.c:1776 slab_free mm/slub.c:3712 [inline] __kmem_cache_free+0xb7/0x1b0 mm/slub.c:3728 kfree+0x6f/0xf0 mm/slab_common.c:990 l2tp_session_free net/l2tp/l2tp_core.c:168 [inline] l2tp_session_put+0xaf/0x1a0 net/l2tp/l2tp_core.c:193 l2tp_session_delete+0x3df/0x4d0 net/l2tp/l2tp_core.c:1587 l2tp_tunnel_closeall net/l2tp/l2tp_core.c:1233 [inline] l2tp_tunnel_del_work+0x199/0x410 net/l2tp/l2tp_core.c:1271 process_one_work+0x717/0xc30 kernel/workqueue.c:2302 worker_thread+0xa4d/0x11d0 kernel/workqueue.c:2449 kthread+0x281/0x320 kernel/kthread.c:386 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295 Last potentially related work creation: kasan_save_stack+0x3a/0x60 mm/kasan/common.c:46 __kasan_record_aux_stack+0xb6/0xc0 mm/kasan/generic.c:486 kasan_record_aux_stack_noalloc+0xb/0x10 mm/kasan/generic.c:496 __call_rcu_common kernel/rcu/tree.c:2807 [inline] call_rcu+0xcf/0xf50 kernel/rcu/tree.c:2926 pppol2tp_release+0x1e3/0x2b0 net/l2tp/l2tp_ppp.c:446 __sock_release net/socket.c:652 [inline] sock_close+0xc9/0x220 net/socket.c:1390 __fput+0x1fd/0x8f0 fs/file_table.c:320 ____fput+0x15/0x20 fs/file_table.c:348 task_work_run+0x1e1/0x250 kernel/task_work.c:203 exit_task_work include/linux/task_work.h:39 [inline] do_exit+0xb0d/0x29f0 kernel/exit.c:896 __do_sys_exit kernel/exit.c:1006 [inline] __se_sys_exit kernel/exit.c:1004 [inline] __cfi___ia32_sys_exit+0x0/0x10 kernel/exit.c:1004 x64_sys_call+0x67/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:61 do_syscall_x64 arch/x86/entry/common.c:46 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76 entry_SYSCALL_64_after_hwframe+0x68/0xd2 The buggy address belongs to the object at ffff88811e200400 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 400 bytes inside of 512-byte region [ffff88811e200400, ffff88811e200600) The buggy address belongs to the physical page: page:ffffea0004788000 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x11e200 head:ffffea0004788000 order:2 compound_mapcount:0 compound_pincount:0 flags: 0x4000000000010200(slab|head|zone=1) raw: 4000000000010200 ffffea0004772600 dead000000000003 ffff888100042f00 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 141, tgid 141 (dhcpcd), ts 7002049555, free_ts 0 set_page_owner include/linux/page_owner.h:33 [inline] post_alloc_hook+0x1f5/0x210 mm/page_alloc.c:2673 prep_new_page+0x1c/0x110 mm/page_alloc.c:2680 get_page_from_freelist+0x2ca9/0x2d20 mm/page_alloc.c:4587 __alloc_pages+0x1fa/0x610 mm/page_alloc.c:5931 alloc_slab_page+0x6e/0xf0 include/linux/gfp.h:-1 allocate_slab mm/slub.c:1967 [inline] new_slab+0x98/0x3e0 mm/slub.c:2020 ___slab_alloc+0x70f/0xb70 mm/slub.c:3177 __slab_alloc+0x5e/0xa0 mm/slub.c:3263 slab_alloc_node mm/slub.c:3348 [inline] __kmem_cache_alloc_node+0x204/0x2d0 mm/slub.c:3423 __do_kmalloc_node mm/slab_common.c:937 [inline] __kmalloc_node_track_caller+0xa1/0x1e0 mm/slab_common.c:958 kmalloc_reserve net/core/skbuff.c:449 [inline] __alloc_skb+0x226/0x4a0 net/core/skbuff.c:518 alloc_skb include/linux/skbuff.h:1322 [inline] alloc_skb_with_frags+0xa8/0x620 net/core/skbuff.c:6189 sock_alloc_send_pskb+0x87f/0x9a0 net/core/sock.c:2770 unix_dgram_sendmsg+0x5c1/0x1710 net/unix/af_unix.c:1959 unix_seqpacket_sendmsg+0x118/0x1e0 net/unix/af_unix.c:2420 sock_sendmsg_nosec net/socket.c:716 [inline] __sock_sendmsg net/socket.c:728 [inline] sock_write_iter+0x2ea/0x3f0 net/socket.c:1134 page_owner free stack trace missing Memory state around the buggy address: ffff88811e200480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88811e200500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff88811e200580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff88811e200600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff88811e200680: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ================================================================== ---------------- Code disassembly (best guess): 0: 89 fe mov %edi,%esi 2: 49 c1 ee 03 shr $0x3,%r14 6: 49 ba 00 00 00 00 00 movabs $0xdffffc0000000000,%r10 d: fc ff df 10: 4f 8d 1c 16 lea (%r14,%r10,1),%r11 14: 4c 8d 44 3e ff lea -0x1(%rsi,%rdi,1),%r8 19: 4d 89 c1 mov %r8,%r9 1c: 49 c1 e9 03 shr $0x3,%r9 20: 4b 8d 1c 29 lea (%r9,%r13,1),%rbx 24: 49 89 dc mov %rbx,%r12 27: 4d 29 dc sub %r11,%r12 * 2a: 49 83 fc 10 cmp $0x10,%r12 <-- trapping instruction 2e: 7f 29 jg 0x59 30: 4d 85 e4 test %r12,%r12 33: 0f 84 45 01 00 00 je 0x17e 39: 4c 89 cb mov %r9,%rbx 3c: 48 f7 d3 not %rbx 3f: 4c rex.WR