================================================================== BUG: KASAN: use-after-free in rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75 Read of size 8 at addr ffff888111320990 by task ksoftirqd/0/13 CPU: 0 PID: 13 Comm: ksoftirqd/0 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026 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+0x47d/0xbf0 kernel/rcu/tree.c:2512 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 373: 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 10: 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:181 exit_to_user_mode_prepare+0x87/0xd0 kernel/entry/common.c:214 __syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline] syscall_exit_to_user_mode+0x1a/0x30 kernel/entry/common.c:307 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 ffff888111320800 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 400 bytes inside of 512-byte region [ffff888111320800, ffff888111320a00) The buggy address belongs to the page: page:ffffea000444c800 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x111320 head:ffffea000444c800 order:2 compound_mapcount:0 compound_pincount:0 flags: 0x4000000000010200(slab|head|zone=1) raw: 4000000000010200 0000000000000000 dead000000000122 ffff888100042f00 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 0x1d20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 369, ts 33832334151, free_ts 33575581367 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] kmem_cache_alloc_trace+0x146/0x270 mm/slub.c:3272 kmalloc include/linux/slab.h:619 [inline] kzalloc include/linux/slab.h:750 [inline] find_css_set+0x91d/0x1560 kernel/cgroup/cgroup.c:1251 cgroup_migrate_prepare_dst+0xc4/0xa00 kernel/cgroup/cgroup.c:2820 cgroup_attach_task+0x298/0x520 kernel/cgroup/cgroup.c:2926 __cgroup1_procs_write+0x314/0x520 kernel/cgroup/cgroup-v1.c:529 cgroup1_procs_write+0x2a/0x40 kernel/cgroup/cgroup-v1.c:543 cgroup_file_write+0x294/0x560 kernel/cgroup/cgroup.c:4011 kernfs_fop_write_iter+0x2bd/0x400 fs/kernfs/file.c:296 call_write_iter include/linux/fs.h:2212 [inline] new_sync_write fs/read_write.c:507 [inline] vfs_write+0x831/0xfd0 fs/read_write.c:594 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_slab+0xe5/0x1e0 mm/slub.c:2025 free_slab mm/slub.c:2040 [inline] discard_slab mm/slub.c:2046 [inline] __unfreeze_partials+0x15a/0x190 mm/slub.c:2532 put_cpu_partial+0xc6/0x120 mm/slub.c:2612 __slab_free+0x1d4/0x290 mm/slub.c:3395 do_slab_free mm/slub.c:3514 [inline] ___cache_free+0x104/0x120 mm/slub.c:3535 qlink_free+0x4d/0x90 mm/kasan/quarantine.c:157 qlist_free_all+0x5f/0xb0 mm/kasan/quarantine.c:176 kasan_quarantine_reduce+0x14a/0x170 mm/kasan/quarantine.c:283 __kasan_slab_alloc+0x2f/0xe0 mm/kasan/common.c:443 kasan_slab_alloc include/linux/kasan.h:217 [inline] slab_post_alloc_hook+0x4f/0x2b0 mm/slab.h:550 slab_alloc_node mm/slub.c:3245 [inline] slab_alloc mm/slub.c:3255 [inline] kmem_cache_alloc+0xf7/0x260 mm/slub.c:3260 kmem_cache_alloc_node include/linux/slab.h:492 [inline] __alloc_skb+0xe4/0x730 net/core/skbuff.c:416 alloc_skb include/linux/skbuff.h:1183 [inline] nlmsg_new include/net/netlink.h:953 [inline] rtmsg_ifinfo_build_skb+0x75/0x180 net/core/rtnetlink.c:3888 Memory state around the buggy address: ffff888111320880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff888111320900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff888111320980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff888111320a00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff888111320a80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc 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