================================================================== BUG: KASAN: use-after-free in l2tp_session_queue_purge+0xf4/0x100 net/l2tp/l2tp_core.c:830 Read of size 4 at addr ffff8801be77f680 by task syz-executor4/13908 CPU: 0 PID: 13908 Comm: syz-executor4 Not tainted 4.4.152-ge5c5f1f #89 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 0000000000000000 a1058cb2a9b10259 ffff8801d4a37cb8 ffffffff81e15fed ffffea0006f9df80 ffff8801be77f680 0000000000000000 ffff8801be77f680 0000000000000000 ffff8801d4a37cf0 ffffffff8151b489 ffff8801be77f680 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 [] 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 Allocated by task 13908: [] 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 13929: [] 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 ffff8801be77f680 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 0 bytes inside of 512-byte region [ffff8801be77f680, ffff8801be77f880) The buggy address belongs to the page: kasan: CONFIG_KASAN_INLINE enabled kasan: GPF could be caused by NULL-ptr deref or user memory accessgeneral protection fault: 0000 [#1] PREEMPT SMP KASAN Dumping ftrace buffer: (ftrace buffer empty) Modules linked in: CPU: 1 PID: 13906 Comm: syz-executor6 Not tainted 4.4.152-ge5c5f1f #89 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 task: ffff8801bb77c800 task.stack: ffff8800a3f10000 RIP: 0010:[] [] lookup_object lib/debugobjects.c:120 [inline] RIP: 0010:[] [] debug_object_free+0xec/0x400 lib/debugobjects.c:559 RSP: 0018:ffff8800a3f17d70 EFLAGS: 00010003 RAX: 0000000000000296 RBX: 4f5f4755425f4d56 RCX: ffffffff81e7823a RDX: 09ebe8eaa84be9ad RSI: 0000000000000008 RDI: 4f5f4755425f4d6e RBP: ffff8800a3f17da8 R08: ffffffff8535ea00 R09: 0000000000000001 R10: 0000000000000001 R11: ffff8801bb77c800 R12: ffffffff85a6fc28 R13: ffff8800a3f17df8 R14: 0000000000000003 R15: dffffc0000000000 FS: 0000000001214940(0063) GS:ffff8801db300000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007ffe0c889fbc CR3: 00000000b2f37000 CR4: 00000000001606f0 Stack: 0000000000000296 ffffffff844c77a0 0000000000000000 0000000000100590 ffff8800a3f17df8 ffff8800a3f17e98 0000000000000001 ffff8800a3f17ec0 ffffffff812a3683 0000000000000000 000000000000c350 1ffff100147e2fbb Call Trace: Code: 78 02 00 00 48 8b 1b 41 be 01 00 00 00 48 85 db 74 44 49 bf 00 00 00 00 00 fc ff df 48 8d 7b 18 41 83 c6 01 48 89 fa 48 c1 ea 03 <42> 80 3c 3a 00 0f 85 0a 02 00 00 4c 3b 6b 18 74 49 48 89 da 48 RIP [] lookup_object lib/debugobjects.c:120 [inline] RIP [] debug_object_free+0xec/0x400 lib/debugobjects.c:559 RSP ---[ end trace 745e92732e86ec72 ]---