================================================================== BUG: KASAN: use-after-free in rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75 Read of size 8 at addr ffff8881393f9590 by task ksoftirqd/1/25 CPU: 1 PID: 25 Comm: ksoftirqd/1 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026 Call Trace: __dump_stack+0x21/0x30 lib/dump_stack.c:88 dump_stack_lvl+0x110/0x170 lib/dump_stack.c:106 print_address_description+0x7f/0x2c0 mm/kasan/report.c:248 __kasan_report mm/kasan/report.c:427 [inline] kasan_report+0x10f/0x150 mm/kasan/report.c:444 __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+0x412/0xbf0 kernel/rcu/tree.c:2510 rcu_core+0x4a3/0xef0 kernel/rcu/tree.c:2763 rcu_core_si+0x9/0x10 kernel/rcu/tree.c:2776 handle_softirqs+0x250/0x560 kernel/softirq.c:583 run_ksoftirqd+0x28/0x40 kernel/softirq.c:959 smpboot_thread_fn+0x446/0x880 kernel/smpboot.c:164 kthread+0x3f5/0x4f0 kernel/kthread.c:337 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287 Allocated by task 4375: 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:433 [inline] ____kasan_kmalloc mm/kasan/common.c:512 [inline] __kasan_kmalloc+0xd4/0x100 mm/kasan/common.c:521 kasan_kmalloc include/linux/kasan.h:227 [inline] __kmalloc+0x13d/0x2c0 mm/slub.c:4436 kmalloc include/linux/slab.h:624 [inline] kzalloc include/linux/slab.h:750 [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:1923 [inline] __sys_connect+0x3cb/0x450 net/socket.c:1940 __do_sys_connect net/socket.c:1950 [inline] __se_sys_connect net/socket.c:1947 [inline] __x64_sys_connect+0x7a/0x90 net/socket.c:1947 x64_sys_call+0x7c/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:43 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x66/0xd0 Freed by task 8: 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:365 __kasan_slab_free+0x11/0x20 mm/kasan/common.c:373 kasan_slab_free include/linux/kasan.h:193 [inline] slab_free_hook mm/slub.c:1728 [inline] slab_free_freelist_hook+0xc2/0x190 mm/slub.c:1754 slab_free mm/slub.c:3526 [inline] kfree+0xc4/0x270 mm/slub.c:4588 l2tp_session_free net/l2tp/l2tp_core.c:168 [inline] l2tp_session_put+0xaf/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+0x6c8/0xbb0 kernel/workqueue.c:2328 worker_thread+0xaa0/0x1250 kernel/workqueue.c:2475 kthread+0x3f5/0x4f0 kernel/kthread.c:337 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287 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_common kernel/rcu/tree.c:3011 [inline] call_rcu+0x10b/0xf60 kernel/rcu/tree.c:3129 pppol2tp_release+0x1e3/0x2b0 net/l2tp/l2tp_ppp.c:447 __sock_release net/socket.c:649 [inline] sock_close+0xb8/0x200 net/socket.c:1336 __fput+0x22b/0x900 fs/file_table.c:311 ____fput+0x15/0x20 fs/file_table.c:339 task_work_run+0x127/0x190 kernel/task_work.c:188 tracehook_notify_resume include/linux/tracehook.h:189 [inline] exit_to_user_mode_loop+0xd0/0xe0 kernel/entry/common.c:184 exit_to_user_mode_prepare+0x87/0xd0 kernel/entry/common.c:217 __syscall_exit_to_user_mode_work kernel/entry/common.c:299 [inline] syscall_exit_to_user_mode+0x1a/0x30 kernel/entry/common.c:310 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86 entry_SYSCALL_64_after_hwframe+0x66/0xd0 The buggy address belongs to the object at ffff8881393f9400 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 400 bytes inside of 512-byte region [ffff8881393f9400, ffff8881393f9600) The buggy address belongs to the page: page:ffffea0004e4fe00 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff8881393fb000 pfn:0x1393f8 head:ffffea0004e4fe00 order:2 compound_mapcount:0 compound_pincount:0 flags: 0x4000000000010200(slab|head|zone=1) raw: 4000000000010200 ffffea0004a6a200 0000000300000003 ffff888100042f00 raw: ffff8881393fb000 0000000080100005 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 0x1d20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 90, ts 103712789692, free_ts 103551586755 set_page_owner include/linux/page_owner.h:33 [inline] post_alloc_hook+0x192/0x1b0 mm/page_alloc.c:2607 prep_new_page+0x1c/0x110 mm/page_alloc.c:2613 get_page_from_freelist+0x2c3a/0x2cd0 mm/page_alloc.c:4487 __alloc_pages+0x1a2/0x460 mm/page_alloc.c:5824 alloc_slab_page mm/slub.c:-1 [inline] allocate_slab mm/slub.c:1937 [inline] new_slab+0xa0/0x4d0 mm/slub.c:2000 ___slab_alloc+0x3ac/0x840 mm/slub.c:3033 __slab_alloc+0x49/0x90 mm/slub.c:3120 slab_alloc_node mm/slub.c:3211 [inline] slab_alloc mm/slub.c:3255 [inline] __kmalloc_track_caller+0x169/0x2c0 mm/slub.c:4954 kmalloc_reserve net/core/skbuff.c:357 [inline] __alloc_skb+0x210/0x730 net/core/skbuff.c:428 alloc_skb include/linux/skbuff.h:1183 [inline] alloc_skb_with_frags+0xa8/0x620 net/core/skbuff.c:6223 sock_alloc_send_pskb+0x87f/0x9a0 net/core/sock.c:2541 unix_dgram_sendmsg+0x6f3/0x19b0 net/unix/af_unix.c:1816 sock_sendmsg_nosec net/socket.c:704 [inline] __sock_sendmsg net/socket.c:716 [inline] __sys_sendto+0x46d/0x620 net/socket.c:2063 __do_sys_sendto net/socket.c:2075 [inline] __se_sys_sendto net/socket.c:2071 [inline] __x64_sys_sendto+0xe5/0x100 net/socket.c:2071 x64_sys_call+0x178/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:45 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80 page last free stack trace: reset_page_owner include/linux/page_owner.h:26 [inline] free_pages_prepare mm/page_alloc.c:1474 [inline] free_pcp_prepare mm/page_alloc.c:1546 [inline] free_unref_page_prepare+0x5fa/0x600 mm/page_alloc.c:3536 free_unref_page+0xae/0x540 mm/page_alloc.c:3618 free_the_page mm/page_alloc.c:805 [inline] __free_pages+0x6c/0x100 mm/page_alloc.c:5900 free_pages+0x82/0x90 mm/page_alloc.c:5911 kasan_depopulate_vmalloc_pte+0x6b/0x90 mm/kasan/shadow.c:354 apply_to_pte_range mm/memory.c:2645 [inline] apply_to_pmd_range mm/memory.c:2689 [inline] apply_to_pud_range mm/memory.c:2725 [inline] apply_to_p4d_range mm/memory.c:2761 [inline] __apply_to_page_range+0x8ca/0xc70 mm/memory.c:2797 apply_to_existing_page_range+0x38/0x50 mm/memory.c:2830 kasan_release_vmalloc+0x97/0xb0 mm/kasan/shadow.c:464 __purge_vmap_area_lazy+0xa8d/0x1890 mm/vmalloc.c:1723 _vm_unmap_aliases+0x2f1/0x370 mm/vmalloc.c:2126 vm_unmap_aliases+0x19/0x20 mm/vmalloc.c:2149 change_page_attr_set_clr+0x317/0xc30 arch/x86/mm/pat/set_memory.c:1740 change_page_attr_clear arch/x86/mm/pat/set_memory.c:1797 [inline] set_memory_ro+0x89/0xd0 arch/x86/mm/pat/set_memory.c:1943 bpf_jit_binary_lock_ro include/linux/filter.h:919 [inline] bpf_int_jit_compile+0xbf12/0xc4c0 arch/x86/net/bpf_jit_comp.c:2478 bpf_prog_select_runtime+0x6ea/0x9e0 kernel/bpf/core.c:1947 bpf_migrate_filter net/core/filter.c:1307 [inline] bpf_prepare_filter+0x100e/0x11b0 net/core/filter.c:1355 Memory state around the buggy address: ffff8881393f9480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8881393f9500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff8881393f9580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff8881393f9600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff8881393f9680: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ==================================================================