================================================================== BUG: KASAN: use-after-free in rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75 Read of size 8 at addr ffff888110dae990 by task udevd/381 CPU: 1 PID: 381 Comm: udevd Tainted: G W 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: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:__sbitmap_queue_get+0xa0/0x220 lib/sbitmap.c:435 Code: ed 00 00 00 4d 89 ee e8 ae af 0b ff 49 8d 5f 34 49 89 dd 49 c1 ed 03 43 0f b6 44 35 00 84 c0 0f 85 42 01 00 00 41 0f b6 57 34 <4c> 89 ff 44 89 e6 e8 05 d8 ff ff 41 89 c7 bf ff ff ff ff 89 c6 e8 RSP: 0018:ffffc9000a39eb50 EFLAGS: 00000246 RAX: 0000000000000000 RBX: ffff8881096d5054 RCX: ffff888111354f00 RDX: 0000000000000000 RSI: 0000000000000080 RDI: 0000000000000034 RBP: ffffc9000a39eb90 R08: ffffc9000a39ecaf R09: ffffc9000a39eca0 R10: dffffc0000000000 R11: fffff52001473d96 R12: 0000000000000034 R13: 1ffff110212daa0a R14: dffffc0000000000 R15: ffff8881096d5020 __blk_mq_get_tag+0x18e/0x4c0 block/blk-mq-tag.c:86 blk_mq_get_tag+0x285/0xa80 block/blk-mq-tag.c:110 __blk_mq_alloc_request+0x3ce/0x4f0 block/blk-mq.c:390 blk_mq_submit_bio+0x388/0x1820 block/blk-mq.c:2249 __submit_bio_noacct_mq block/blk-core.c:1020 [inline] submit_bio_noacct+0xb6e/0xe50 block/blk-core.c:1053 submit_bio+0x342/0x710 block/blk-core.c:1123 mpage_bio_submit+0xfd/0x520 fs/mpage.c:102 mpage_readahead+0x463/0x560 fs/mpage.c:429 blkdev_readahead+0x1c/0x20 fs/block_dev.c:653 read_pages+0x17b/0xb50 mm/readahead.c:140 page_cache_ra_unbounded+0x638/0x790 mm/readahead.c:248 do_page_cache_ra mm/readahead.c:277 [inline] force_page_cache_ra+0x3a7/0x400 mm/readahead.c:308 page_cache_sync_ra+0x237/0x2a0 mm/readahead.c:582 page_cache_sync_readahead include/linux/pagemap.h:837 [inline] generic_file_buffered_read+0x570/0x26d0 mm/filemap.c:2250 generic_file_read_iter+0x10b/0x580 mm/filemap.c:2568 blkdev_read_iter+0x12f/0x160 fs/block_dev.c:1956 call_read_iter include/linux/fs.h:2060 [inline] new_sync_read fs/read_write.c:415 [inline] vfs_read+0x62a/0xa50 fs/read_write.c:496 ksys_read+0x14a/0x260 fs/read_write.c:634 __do_sys_read fs/read_write.c:644 [inline] __se_sys_read fs/read_write.c:642 [inline] __x64_sys_read+0x7b/0x90 fs/read_write.c:642 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x61/0xcb RIP: 0033:0x7f37a5332407 Code: 48 89 fa 4c 89 df e8 38 aa 00 00 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 1a 5b c3 0f 1f 84 00 00 00 00 00 48 8b 44 24 10 0f 05 <5b> c3 0f 1f 80 00 00 00 00 83 e2 39 83 fa 08 75 de e8 23 ff ff ff RSP: 002b:00007ffe285ef0b0 EFLAGS: 00000202 ORIG_RAX: 0000000000000000 RAX: ffffffffffffffda RBX: 00007f37a5244880 RCX: 00007f37a5332407 RDX: 0000000000000200 RSI: 00007f37a50a0000 RDI: 0000000000000009 RBP: 0000556dc2fd3790 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000000 R13: 0000000000000000 R14: 0000556dc2fe32a8 R15: 00007f37a5a8839c Allocated by task 1761: 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:1866 [inline] __sys_connect+0x3ce/0x450 net/socket.c:1883 __do_sys_connect net/socket.c:1893 [inline] __se_sys_connect net/socket.c:1890 [inline] __x64_sys_connect+0x7a/0x90 net/socket.c:1890 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x61/0xcb Freed by task 48: 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:1286 __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 exit_task_work include/linux/task_work.h:33 [inline] do_exit+0xa7c/0x24e0 kernel/exit.c:873 do_group_exit+0x149/0x310 kernel/exit.c:987 get_signal+0xfb1/0x1300 kernel/signal.c:2793 arch_do_signal_or_restart+0xe7/0x11b0 arch/x86/kernel/signal.c:805 handle_signal_work kernel/entry/common.c:145 [inline] exit_to_user_mode_loop+0xa2/0xe0 kernel/entry/common.c:169 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 ffff888110dae800 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 400 bytes inside of 512-byte region [ffff888110dae800, ffff888110daea00) The buggy address belongs to the page: page:ffffea0004436b00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x110dac head:ffffea0004436b00 order:2 compound_mapcount:0 compound_pincount:0 flags: 0x4000000000010200(slab|head) raw: 4000000000010200 ffffea0004693700 0000000200000002 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 0x1d2a20(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 15, ts 25199678797, free_ts 25198243654 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] ndisc_alloc_skb net/ipv6/ndisc.c:422 [inline] ndisc_send_ns+0x347/0xb10 net/ipv6/ndisc.c:631 addrconf_dad_work+0xa40/0x1480 net/ipv6/addrconf.c:4210 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 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_pages_ok+0x80b/0x830 mm/page_alloc.c:1629 free_the_page mm/page_alloc.c:5445 [inline] __free_pages+0xd8/0x390 mm/page_alloc.c:5454 __free_slab+0xcf/0x190 mm/slub.c:1899 free_slab mm/slub.c:1914 [inline] discard_slab mm/slub.c:1920 [inline] unfreeze_partials+0x150/0x180 mm/slub.c:2415 put_cpu_partial+0xc1/0x180 mm/slub.c:2451 __slab_free+0x2c9/0x3a0 mm/slub.c:3100 do_slab_free mm/slub.c:3196 [inline] ___cache_free+0x10e/0x130 mm/slub.c:3215 qlink_free+0x50/0x90 mm/kasan/quarantine.c:157 qlist_free_all+0x5f/0xb0 mm/kasan/quarantine.c:176 kasan_quarantine_reduce+0x14a/0x160 mm/kasan/quarantine.c:283 __kasan_slab_alloc+0x2f/0xe0 mm/kasan/common.c:440 kasan_slab_alloc include/linux/kasan.h:244 [inline] slab_post_alloc_hook+0x5d/0x2f0 mm/slab.h:580 slab_alloc_node mm/slub.c:2952 [inline] slab_alloc mm/slub.c:2960 [inline] kmem_cache_alloc+0x15a/0x2d0 mm/slub.c:2965 kmem_cache_alloc_node include/linux/slab.h:426 [inline] __alloc_skb+0x9e/0x520 net/core/skbuff.c:200 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:1889 sock_sendmsg_nosec net/socket.c:652 [inline] __sock_sendmsg net/socket.c:664 [inline] __sys_sendto+0x467/0x620 net/socket.c:2006 Memory state around the buggy address: ffff888110dae880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff888110dae900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff888110dae980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff888110daea00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff888110daea80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ================================================================== ---------------- Code disassembly (best guess): 0: ed in (%dx),%eax 1: 00 00 add %al,(%rax) 3: 00 4d 89 add %cl,-0x77(%rbp) 6: ee out %al,(%dx) 7: e8 ae af 0b ff call 0xff0bafba c: 49 8d 5f 34 lea 0x34(%r15),%rbx 10: 49 89 dd mov %rbx,%r13 13: 49 c1 ed 03 shr $0x3,%r13 17: 43 0f b6 44 35 00 movzbl 0x0(%r13,%r14,1),%eax 1d: 84 c0 test %al,%al 1f: 0f 85 42 01 00 00 jne 0x167 25: 41 0f b6 57 34 movzbl 0x34(%r15),%edx * 2a: 4c 89 ff mov %r15,%rdi <-- trapping instruction 2d: 44 89 e6 mov %r12d,%esi 30: e8 05 d8 ff ff call 0xffffd83a 35: 41 89 c7 mov %eax,%r15d 38: bf ff ff ff ff mov $0xffffffff,%edi 3d: 89 c6 mov %eax,%esi 3f: e8 .byte 0xe8