================================================================== BUG: KASAN: use-after-free in l2tp_session_queue_purge+0xf4/0x100 net/l2tp/l2tp_core.c:830 Read of size 4 at addr ffff8800b5e53680 by task syz-executor3/5935 CPU: 0 PID: 5935 Comm: syz-executor3 Not tainted 4.4.152-ge5c5f1f #89 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 TCP: request_sock_TCPv6: Possible SYN flooding on port 20002. Sending cookies. Check SNMP counters. 0000000000000000 c221f2064604424f ffff8800a451fa78 ffffffff81e15fed ffffea0002d79480 ffff8800b5e53680 0000000000000000 ffff8800b5e53680 0000000000000000 ffff8800a451fab0 ffffffff8151b489 ffff8800b5e53680 Call Trace: [] __dump_stack lib/dump_stack.c:15 [inline] [] dump_stack+0xc1/0x124 lib/dump_stack.c:51 [] print_address_description+0x6c/0x216 mm/kasan/report.c:252 [] kasan_report_error mm/kasan/report.c:351 [inline] [] kasan_report.cold.7+0x175/0x2f7 mm/kasan/report.c:408 [] __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:428 [] l2tp_session_queue_purge+0xf4/0x100 net/l2tp/l2tp_core.c:830 [] pppol2tp_release+0x1ff/0x310 net/l2tp/l2tp_ppp.c:509 [] __sock_release+0xd9/0x260 net/socket.c:592 [] sock_close+0x19/0x20 net/socket.c:1050 [] __fput+0x235/0x6f0 fs/file_table.c:208 [] ____fput+0x15/0x20 fs/file_table.c:244 [] task_work_run+0x10f/0x190 kernel/task_work.c:115 [] get_signal+0x1190/0x14b0 kernel/signal.c:2151 [] do_signal+0x8b/0x1d30 arch/x86/kernel/signal.c:712 [] exit_to_usermode_loop+0x11a/0x160 arch/x86/entry/common.c:249 [] prepare_exit_to_usermode arch/x86/entry/common.c:284 [inline] [] syscall_return_slowpath+0x1b5/0x1f0 arch/x86/entry/common.c:349 [] int_ret_from_sys_call+0x25/0xa3 Allocated by task 5912: [] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63 [] save_stack+0x43/0xd0 mm/kasan/kasan.c:512 [] set_track mm/kasan/kasan.c:524 [inline] [] kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:616 [] __kmalloc+0x124/0x310 mm/slub.c:3613 [] kmalloc include/linux/slab.h:481 [inline] [] kzalloc include/linux/slab.h:620 [inline] [] l2tp_session_create+0x39/0x1030 net/l2tp/l2tp_core.c:1748 [] pppol2tp_connect+0x10f0/0x1910 net/l2tp/l2tp_ppp.c:725 [] SYSC_connect+0x1b8/0x300 net/socket.c:1570 [] SyS_connect+0x24/0x30 net/socket.c:1551 [] entry_SYSCALL_64_fastpath+0x22/0x9e Freed by task 5955: [] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63 [] save_stack+0x43/0xd0 mm/kasan/kasan.c:512 [] set_track mm/kasan/kasan.c:524 [inline] [] kasan_slab_free+0x72/0xc0 mm/kasan/kasan.c:589 [] slab_free_hook mm/slub.c:1383 [inline] [] slab_free_freelist_hook mm/slub.c:1405 [inline] [] slab_free mm/slub.c:2859 [inline] [] kfree+0xf4/0x310 mm/slub.c:3749 [] l2tp_session_free+0x170/0x200 net/l2tp/l2tp_core.c:1676 [] l2tp_session_dec_refcount_1 net/l2tp/l2tp_core.h:293 [inline] [] l2tp_tunnel_closeall+0x2b9/0x350 net/l2tp/l2tp_core.c:1279 [] l2tp_udp_encap_destroy+0x8b/0xf0 net/l2tp/l2tp_core.c:1300 [] udpv6_destroy_sock+0xb1/0xd0 net/ipv6/udp.c:1421 [] sk_common_release+0x6d/0x300 net/core/sock.c:2680 [] udp_lib_close+0x15/0x20 include/net/udp.h:190 [] inet_release+0xff/0x1d0 net/ipv4/af_inet.c:435 [] inet6_release+0x50/0x70 net/ipv6/af_inet6.c:424 [] __sock_release+0xd9/0x260 net/socket.c:592 [] sock_close+0x19/0x20 net/socket.c:1050 [] __fput+0x235/0x6f0 fs/file_table.c:208 [] ____fput+0x15/0x20 fs/file_table.c:244 [] task_work_run+0x10f/0x190 kernel/task_work.c:115 [] tracehook_notify_resume include/linux/tracehook.h:191 [inline] [] exit_to_usermode_loop+0x13d/0x160 arch/x86/entry/common.c:253 [] prepare_exit_to_usermode arch/x86/entry/common.c:284 [inline] [] syscall_return_slowpath+0x1b5/0x1f0 arch/x86/entry/common.c:349 [] int_ret_from_sys_call+0x25/0xa3 The buggy address belongs to the object at ffff8800b5e53680 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 0 bytes inside of 512-byte region [ffff8800b5e53680, ffff8800b5e53880) The buggy address belongs to the page: BUG: unable to handle kernel paging request at fffffffd33cb2a80 IP: [] cpuacct_charge+0x155/0x380 kernel/sched/cpuacct.c:247 PGD 440f067 PUD 0 Oops: 0000 [#1] PREEMPT SMP KASAN Dumping ftrace buffer: (ftrace buffer empty) Modules linked in: CPU: 1 PID: 3653 Comm: syz-fuzzer Not tainted 4.4.152-ge5c5f1f #89 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 task: ffff8800b36d0000 task.stack: ffff8801cfff0000 RIP: 0010:[] [] cpuacct_charge+0x155/0x380 kernel/sched/cpuacct.c:247 RSP: 0018:ffff8801cfff7ca0 EFLAGS: 00010046 RAX: 1ffffffff089521f RBX: 00000000000185a8 RCX: ffffffff84a16680 RDX: fffffbffa6796550 RSI: fffffffd33cb2a80 RDI: ffffffff844a90f8 RBP: ffff8801cfff7ce0 R08: ffff8800b36d0978 R09: 0000000000000001 R10: 0000000000000001 R11: ffff8800b36d0000 R12: ffffffff844a9020 R13: dffffc0000000000 R14: 000000000e01a133 R15: ffffffffb5e53880 FS: 000000c420028e68(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: fffffffd33cb2a80 CR3: 00000000b3734000 CR4: 00000000001606f0 Stack: ffffffff81227c90 0000000000000046 0000000000000003 ffff8800a4b88060 ffff8800a4b88000 000000000e01a133 ffff8800a4b880b0 0000000000000000 ffff8801cfff7d28 ffffffff811dc309 0000000000000005 ffff8801db21f558 Call Trace: [] update_curr+0x2c9/0x6d0 kernel/sched/fair.c:882 [] enqueue_entity kernel/sched/fair.c:3512 [inline] [] enqueue_task_fair+0x2fa/0x2790 kernel/sched/fair.c:4695 [] enqueue_task kernel/sched/core.c:858 [inline] [] activate_task+0x14d/0x280 kernel/sched/core.c:874 [] ttwu_activate kernel/sched/core.c:1736 [inline] [] ttwu_do_activate.constprop.109+0xbf/0x1e0 kernel/sched/core.c:1789 [] ttwu_queue kernel/sched/core.c:1934 [inline] [] try_to_wake_up+0x660/0xf00 kernel/sched/core.c:2068 [] wake_up_state+0x10/0x20 kernel/sched/core.c:2148 [] signal_wake_up_state+0x44/0x70 kernel/signal.c:659 [] signal_wake_up include/linux/sched.h:3332 [inline] [] zap_other_threads+0x123/0x170 kernel/signal.c:1213 [] do_group_exit+0x26c/0x330 kernel/exit.c:880 [] SYSC_exit_group kernel/exit.c:896 [inline] [] SyS_exit_group+0x1d/0x20 kernel/exit.c:894 [] entry_SYSCALL_64_fastpath+0x22/0x9e Code: 49 8d bc 24 d8 00 00 00 48 89 f8 48 c1 e8 03 42 80 3c 28 00 0f 85 c4 01 00 00 49 8b 9c 24 d8 00 00 00 80 3a 00 0f 85 8f 01 00 00 <4a> 03 1c f9 48 89 d8 48 c1 e8 03 42 80 3c 28 00 0f 85 be 01 00 RIP [] cpuacct_charge+0x155/0x380 kernel/sched/cpuacct.c:247 RSP CR2: fffffffd33cb2a80 ---[ end trace 6926d836b48180ba ]---