================================================================== BUG: KASAN: use-after-free in rcu_segcblist_enqueue+0x9c/0xb0 kernel/rcu/rcu_segcblist.c:346 Write of size 8 at addr ffff8881193ac990 by task syz.1.348/1171 CPU: 1 PID: 1171 Comm: syz.1.348 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026 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_store8_noabort+0x17/0x20 mm/kasan/report_generic.c:356 rcu_segcblist_enqueue+0x9c/0xb0 kernel/rcu/rcu_segcblist.c:346 __call_rcu_common kernel/rcu/tree.c:2827 [inline] call_rcu+0x918/0xf90 kernel/rcu/tree.c:2926 security_inode_free+0xc5/0xe0 security/security.c:1073 __destroy_inode+0x17a/0x530 fs/inode.c:289 destroy_inode fs/inode.c:312 [inline] evict+0x79b/0x8f0 fs/inode.c:723 iput_final fs/inode.c:1844 [inline] iput+0x620/0x670 fs/inode.c:1870 dentry_unlink_inode+0x33d/0x3f0 fs/dcache.c:405 __dentry_kill+0x460/0x670 fs/dcache.c:611 dentry_kill+0xc0/0x2a0 fs/dcache.c:-1 dput+0x42/0x80 fs/dcache.c:918 __fput+0x5be/0x8f0 fs/file_table.c:328 ____fput+0x15/0x20 fs/file_table.c:348 task_work_run+0x1e1/0x250 kernel/task_work.c:203 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline] exit_to_user_mode_loop+0x9b/0xb0 kernel/entry/common.c:177 exit_to_user_mode_prepare+0x87/0xd0 kernel/entry/common.c:210 __syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline] syscall_exit_to_user_mode+0x1a/0x30 kernel/entry/common.c:303 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:82 entry_SYSCALL_64_after_hwframe+0x68/0xd2 RIP: 0033:0x7fdd74f9ce59 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:00007ffc3c0a92d8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4 RAX: 0000000000000000 RBX: 00007ffc3c0a93c0 RCX: 00007fdd74f9ce59 RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003 RBP: 0000000000009d0f R08: 0000000000000001 R09: 0000000000000000 R10: 0000001b2db20000 R11: 0000000000000246 R12: 00007ffc3c0a9400 R13: 00007fdd75215fac R14: 0000000000009d42 R15: 00007fdd75215fa0 Allocated by task 1172: kasan_save_stack mm/kasan/common.c:46 [inline] kasan_set_track+0x4b/0x70 mm/kasan/common.c:53 kasan_save_alloc_info+0x25/0x30 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+0xb1/0x1e0 mm/slab_common.c:951 kmalloc include/linux/slab.h:568 [inline] kzalloc include/linux/slab.h:699 [inline] l2tp_session_create+0x38/0xbe0 net/l2tp/l2tp_core.c:1609 pppol2tp_connect+0xbef/0x1620 net/l2tp/l2tp_ppp.c:771 __sys_connect_file net/socket.c:2000 [inline] __sys_connect+0x3da/0x460 net/socket.c:2017 __do_sys_connect net/socket.c:2027 [inline] __se_sys_connect net/socket.c:2024 [inline] __x64_sys_connect+0x7a/0x90 net/socket.c:2024 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 358: kasan_save_stack mm/kasan/common.c:46 [inline] kasan_set_track+0x4b/0x70 mm/kasan/common.c:53 kasan_save_free_info+0x31/0x50 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+0x3f0/0x4e0 net/l2tp/l2tp_core.c:1582 l2tp_tunnel_closeall net/l2tp/l2tp_core.c:1228 [inline] l2tp_tunnel_del_work+0x1a1/0x410 net/l2tp/l2tp_core.c:1266 process_one_work+0x71f/0xc40 kernel/workqueue.c:2302 worker_thread+0xa29/0x11e0 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/0xf90 kernel/rcu/tree.c:2926 pppol2tp_release+0x208/0x2d0 net/l2tp/l2tp_ppp.c:446 __sock_release net/socket.c:652 [inline] sock_close+0xf1/0x290 net/socket.c:1389 __fput+0x1fc/0x8f0 fs/file_table.c:320 ____fput+0x15/0x20 fs/file_table.c:348 task_work_run+0x1e1/0x250 kernel/task_work.c:203 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline] exit_to_user_mode_loop+0x9b/0xb0 kernel/entry/common.c:177 exit_to_user_mode_prepare+0x87/0xd0 kernel/entry/common.c:210 __syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline] syscall_exit_to_user_mode+0x1a/0x30 kernel/entry/common.c:303 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:82 entry_SYSCALL_64_after_hwframe+0x68/0xd2 The buggy address belongs to the object at ffff8881193ac800 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 400 bytes inside of 512-byte region [ffff8881193ac800, ffff8881193aca00) The buggy address belongs to the physical page: page:ffffea000464eb00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1193ac head:ffffea000464eb00 order:2 compound_mapcount:0 compound_pincount:0 flags: 0x4000000000010200(slab|head|zone=1) raw: 4000000000010200 dead000000000100 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 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 108, tgid 108 (udevd), ts 4376115633, free_ts 0 set_page_owner include/linux/page_owner.h:33 [inline] post_alloc_hook+0x1f5/0x210 mm/page_alloc.c:2672 prep_new_page+0x1c/0x110 mm/page_alloc.c:2679 get_page_from_freelist+0x2d12/0x2d80 mm/page_alloc.c:4585 __alloc_pages+0x1fa/0x610 mm/page_alloc.c:5929 alloc_slab_page+0x6e/0xf0 include/linux/gfp.h:-1 allocate_slab mm/slub.c:1967 [inline] new_slab+0x98/0x3d0 mm/slub.c:2020 ___slab_alloc+0x6bd/0xb20 mm/slub.c:3177 __slab_alloc+0x5e/0xa0 mm/slub.c:3263 slab_alloc_node mm/slub.c:3348 [inline] __kmem_cache_alloc_node+0x203/0x2c0 mm/slub.c:3423 __do_kmalloc_node mm/slab_common.c:937 [inline] __kmalloc_node_track_caller+0xa0/0x1e0 mm/slab_common.c:958 kmalloc_reserve net/core/skbuff.c:449 [inline] __alloc_skb+0x236/0x4b0 net/core/skbuff.c:518 alloc_skb include/linux/skbuff.h:1322 [inline] alloc_skb_with_frags+0xa8/0x620 net/core/skbuff.c:6176 sock_alloc_send_pskb+0x87f/0x9a0 net/core/sock.c:2761 unix_dgram_sendmsg+0x539/0x16f0 net/unix/af_unix.c:1947 sock_sendmsg_nosec net/socket.c:716 [inline] __sock_sendmsg net/socket.c:728 [inline] sock_write_iter+0x2ee/0x3f0 net/socket.c:1133 call_write_iter include/linux/fs.h:2282 [inline] new_sync_write fs/read_write.c:491 [inline] vfs_write+0x603/0xce0 fs/read_write.c:584 page_owner free stack trace missing Memory state around the buggy address: ffff8881193ac880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8881193ac900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff8881193ac980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff8881193aca00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff8881193aca80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ==================================================================