================================================================== BUG: KASAN: use-after-free in rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75 Read of size 8 at addr ffff88810eba9590 by task udevd/301 CPU: 0 PID: 301 Comm: udevd Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026 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:__mnt_want_write+0x5d/0x260 fs/namespace.c:332 Code: d8 48 c1 e8 03 48 89 45 c0 42 80 3c 28 00 74 08 48 89 df e8 c5 ce f0 ff 48 89 5d d0 49 8b 46 48 65 ff 40 04 f0 83 44 24 fc 00 <49> 8d 5e 10 49 89 df 49 c1 ef 03 43 0f b6 04 2f 84 c0 0f 85 8f 01 RSP: 0018:ffffc90007987bb0 EFLAGS: 00000286 RAX: 0000607e08c09e50 RBX: ffff8881057a2e68 RCX: ffffffff86e81800 RDX: 0000000000000000 RSI: 0000000080000000 RDI: ffffffff81ae586d RBP: ffffc90007987bf0 R08: ffffc90007987cef R09: ffffc90007987ca0 R10: dffffc0000000000 R11: fffff52000f30f9e R12: ffff88810029f2a8 R13: dffffc0000000000 R14: ffff8881057a2e20 R15: 0000000080000000 mnt_want_write+0xe2/0x270 fs/namespace.c:364 vfs_utimes+0x284/0x5b0 fs/utimes.c:35 do_utimes_path fs/utimes.c:97 [inline] do_utimes+0x1ad/0x2a0 fs/utimes.c:143 __do_sys_utimensat fs/utimes.c:162 [inline] __se_sys_utimensat fs/utimes.c:146 [inline] __x64_sys_utimensat+0x15b/0x240 fs/utimes.c:146 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x61/0xcb RIP: 0033:0x7ff4bd37fa1a Code: 77 06 c3 0f 1f 44 00 00 48 8b 15 d9 b3 0d 00 f7 d8 64 89 02 b8 ff ff ff ff c3 66 0f 1f 44 00 00 41 89 ca b8 18 01 00 00 0f 05 <48> 3d 00 f0 ff ff 77 06 c3 0f 1f 44 00 00 48 8b 15 a9 b3 0d 00 f7 RSP: 002b:00007ffd04753d68 EFLAGS: 00000246 ORIG_RAX: 0000000000000118 RAX: ffffffffffffffda RBX: 00007ffd04754740 RCX: 00007ff4bd37fa1a RDX: 0000000000000000 RSI: 00007ffd04754740 RDI: 00000000ffffff9c RBP: 00007ffd04754751 R08: 0000000000000030 R09: 000055e7e25ee450 R10: 0000000000000100 R11: 0000000000000246 R12: 00007ffd04754220 R13: 00007ffd04753e20 R14: 000055e7c9bd56d7 R15: 000055e7e282ef90 Allocated by task 840: 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 49: 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:172 exit_to_user_mode_prepare+0x76/0xa0 kernel/entry/common.c:199 syscall_exit_to_user_mode+0x1d/0x40 kernel/entry/common.c:274 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 ffff88810eba9400 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 400 bytes inside of 512-byte region [ffff88810eba9400, ffff88810eba9600) The buggy address belongs to the page: page:ffffea00043aea00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x10eba8 head:ffffea00043aea00 order:2 compound_mapcount:0 compound_pincount:0 flags: 0x4000000000010200(slab|head) raw: 4000000000010200 ffffea00043b7d00 0000000700000007 ffff888100043080 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 0x1d20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 283, ts 26064225663, free_ts 26029929920 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_track_caller+0x1e4/0x310 mm/slub.c:4541 __kmalloc_reserve net/core/skbuff.c:144 [inline] __alloc_skb+0xdc/0x520 net/core/skbuff.c:212 alloc_skb include/linux/skbuff.h:1126 [inline] netlink_alloc_large_skb net/netlink/af_netlink.c:1178 [inline] netlink_sendmsg+0x693/0xb70 net/netlink/af_netlink.c:1894 sock_sendmsg_nosec net/socket.c:652 [inline] __sock_sendmsg net/socket.c:664 [inline] __sys_sendto+0x467/0x620 net/socket.c:2007 __do_sys_sendto net/socket.c:2019 [inline] __se_sys_sendto net/socket.c:2015 [inline] __x64_sys_sendto+0xe5/0x100 net/socket.c:2015 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x61/0xcb 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 mm/page_alloc.c:3391 [inline] free_the_page mm/page_alloc.c:5443 [inline] __free_pages+0x146/0x390 mm/page_alloc.c:5454 __vunmap+0x801/0x980 mm/vmalloc.c:2307 __vfree mm/vmalloc.c:2356 [inline] vfree+0x61/0x90 mm/vmalloc.c:2387 htable_put+0x5fb/0x650 net/netfilter/xt_hashlimit.c:432 hashlimit_mt_destroy_v1+0x58/0x60 net/netfilter/xt_hashlimit.c:970 cleanup_match net/ipv4/netfilter/ip_tables.c:460 [inline] cleanup_entry+0x14d/0x330 net/ipv4/netfilter/ip_tables.c:645 translate_table+0x1d60/0x1f60 net/ipv4/netfilter/ip_tables.c:728 do_replace net/ipv4/netfilter/ip_tables.c:1136 [inline] do_ipt_set_ctl+0x957/0xd70 net/ipv4/netfilter/ip_tables.c:1633 nf_setsockopt+0x272/0x2a0 net/netfilter/nf_sockopt.c:101 ip_setsockopt+0x29f2/0x35b0 net/ipv4/ip_sockglue.c:1442 udp_setsockopt+0x8a/0xa0 net/ipv4/udp.c:2750 sock_common_setsockopt+0xa0/0xb0 net/core/sock.c:3327 __sys_setsockopt+0x2fa/0x480 net/socket.c:2147 __do_sys_setsockopt net/socket.c:2158 [inline] __se_sys_setsockopt net/socket.c:2155 [inline] __x64_sys_setsockopt+0xbf/0xd0 net/socket.c:2155 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46 Memory state around the buggy address: ffff88810eba9480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88810eba9500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff88810eba9580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff88810eba9600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff88810eba9680: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ================================================================== ---------------- Code disassembly (best guess): 0: d8 48 c1 fmuls -0x3f(%rax) 3: e8 03 48 89 45 call 0x4589480b 8: c0 42 80 3c rolb $0x3c,-0x80(%rdx) c: 28 00 sub %al,(%rax) e: 74 08 je 0x18 10: 48 89 df mov %rbx,%rdi 13: e8 c5 ce f0 ff call 0xfff0cedd 18: 48 89 5d d0 mov %rbx,-0x30(%rbp) 1c: 49 8b 46 48 mov 0x48(%r14),%rax 20: 65 ff 40 04 incl %gs:0x4(%rax) 24: f0 83 44 24 fc 00 lock addl $0x0,-0x4(%rsp) * 2a: 49 8d 5e 10 lea 0x10(%r14),%rbx <-- trapping instruction 2e: 49 89 df mov %rbx,%r15 31: 49 c1 ef 03 shr $0x3,%r15 35: 43 0f b6 04 2f movzbl (%r15,%r13,1),%eax 3a: 84 c0 test %al,%al 3c: 0f .byte 0xf 3d: 85 .byte 0x85 3e: 8f 01 pop (%rcx)