================================================================== BUG: KASAN: use-after-free in rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75 Read of size 8 at addr ffff88811b436d90 by task syz.4.1198/5558 CPU: 1 PID: 5558 Comm: syz.4.1198 Tainted: G W syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/06/2026 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+0x3e2/0xaf0 kernel/rcu/tree.c:2483 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:selinux_file_permission+0x3fc/0x510 security/selinux/hooks.c:3628 Code: 1c 7b eb 0b e8 95 1e 4a ff 81 cb 00 02 00 00 48 8b 7d d0 4c 89 f6 89 da e8 d1 05 01 00 89 c3 89 d8 48 83 c4 38 5b 41 5c 41 5d <41> 5e 41 5f 5d c3 e8 69 1e 4a ff 45 31 f6 e9 2f fd ff ff e8 5c 1e RSP: 0018:ffffc90001067a48 EFLAGS: 00000296 RAX: 0000000000000000 RBX: 0000000000000004 RCX: 0000000000080000 RDX: ffffc9000b43a000 RSI: 000000000007ffff RDI: 0000000000080000 RBP: ffffc90001067a58 R08: 000000000000000e R09: ffffffff84a000c5 R10: 0000000000000001 R11: 000000009cf31cb9 R12: ffffffff85bf74f0 R13: dffffc0000000000 R14: 0000000000000001 R15: dffffc0000000000 security_file_permission+0x69/0xa0 security/security.c:1435 rw_verify_area+0x1c0/0x360 fs/read_write.c:400 do_splice_to fs/splice.c:782 [inline] splice_direct_to_actor+0x36f/0xb20 fs/splice.c:870 do_splice_direct+0x1c2/0x2d0 fs/splice.c:979 do_sendfile+0x8df/0x1040 fs/read_write.c:1257 __do_sys_sendfile64 fs/read_write.c:1318 [inline] __se_sys_sendfile64 fs/read_write.c:1304 [inline] __x64_sys_sendfile64+0x199/0x1f0 fs/read_write.c:1304 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x61/0xcb RIP: 0033:0x7f8b5be5db19 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:00007f8b5a894028 EFLAGS: 00000246 ORIG_RAX: 0000000000000028 RAX: ffffffffffffffda RBX: 00007f8b5c0e4090 RCX: 00007f8b5be5db19 RDX: 0000000000000000 RSI: 0000000000000008 RDI: 0000000000000009 RBP: 00007f8b5bef5b70 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000040003 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f8b5c0e4128 R14: 00007f8b5c0e4090 R15: 00007ffc5c1bd9e8 Allocated by task 5518: 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 9: 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 get_signal+0x1281/0x1300 kernel/signal.c:2579 arch_do_signal_or_restart+0xe7/0x11b0 arch/x86/kernel/signal.c:805 handle_signal_work kernel/entry/common.c:148 [inline] exit_to_user_mode_loop+0xa2/0xe0 kernel/entry/common.c:172 exit_to_user_mode_prepare+0x76/0xa0 kernel/entry/common.c:202 syscall_exit_to_user_mode+0x1d/0x40 kernel/entry/common.c:277 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 ffff88811b436c00 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 400 bytes inside of 512-byte region [ffff88811b436c00, ffff88811b436e00) The buggy address belongs to the page: page:ffffea00046d0d00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x11b434 head:ffffea00046d0d00 order:2 compound_mapcount:0 compound_pincount:0 flags: 0x4000000000010200(slab|head) raw: 4000000000010200 0000000000000000 0000000100000001 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 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 166, ts 4977965100, free_ts 0 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] kmem_cache_alloc_trace+0x1a8/0x2e0 mm/slub.c:2977 kmalloc include/linux/slab.h:555 [inline] kzalloc include/linux/slab.h:667 [inline] alloc_bprm+0x59/0x630 fs/exec.c:1509 do_execveat_common+0x1b1/0xab0 fs/exec.c:1911 do_execve fs/exec.c:2030 [inline] __do_sys_execve fs/exec.c:2106 [inline] __se_sys_execve fs/exec.c:2101 [inline] __x64_sys_execve+0x92/0xb0 fs/exec.c:2101 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x61/0xcb page_owner free stack trace missing Memory state around the buggy address: ffff88811b436c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88811b436d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff88811b436d80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff88811b436e00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff88811b436e80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ================================================================== ---------------- Code disassembly (best guess): 0: 1c 7b sbb $0x7b,%al 2: eb 0b jmp 0xf 4: e8 95 1e 4a ff call 0xff4a1e9e 9: 81 cb 00 02 00 00 or $0x200,%ebx f: 48 8b 7d d0 mov -0x30(%rbp),%rdi 13: 4c 89 f6 mov %r14,%rsi 16: 89 da mov %ebx,%edx 18: e8 d1 05 01 00 call 0x105ee 1d: 89 c3 mov %eax,%ebx 1f: 89 d8 mov %ebx,%eax 21: 48 83 c4 38 add $0x38,%rsp 25: 5b pop %rbx 26: 41 5c pop %r12 28: 41 5d pop %r13 * 2a: 41 5e pop %r14 <-- trapping instruction 2c: 41 5f pop %r15 2e: 5d pop %rbp 2f: c3 ret 30: e8 69 1e 4a ff call 0xff4a1e9e 35: 45 31 f6 xor %r14d,%r14d 38: e9 2f fd ff ff jmp 0xfffffd6c 3d: e8 .byte 0xe8 3e: 5c pop %rsp 3f: 1e (bad)