netlink: 3 bytes leftover after parsing attributes in process `syz-executor4'. netlink: 3 bytes leftover after parsing attributes in process `syz-executor4'. ================================================================== BUG: KASAN: use-after-free in l2tp_session_queue_purge+0xf4/0x100 net/l2tp/l2tp_core.c:830 Read of size 4 at addr ffff8801d4a06280 by task syz-executor0/8613 CPU: 1 PID: 8613 Comm: syz-executor0 Not tainted 4.4.151-g727cfac #87 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 0000000000000000 c1eed10879728d33 ffff8801bd39fcb8 ffffffff81e15eed ffffea0007528180 ffff8801d4a06280 0000000000000000 ffff8801d4a06280 0000000000000000 ffff8801bd39fcf0 ffffffff8151b390 ffff8801d4a06280 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 8593: [] 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 8593: [] 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 ffff8801d4a06280 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 0 bytes inside of 512-byte region [ffff8801d4a06280, ffff8801d4a06480) 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: 0 PID: 8587 Comm: syz-executor5 Not tainted 4.4.151-g727cfac #87 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 task: ffff8801bdb3c800 task.stack: ffff8800a4498000 RIP: 0010:[] [] try_to_wake_up+0x20b/0xf00 kernel/sched/core.c:2045 RSP: 0018:ffff8800a449fe18 EFLAGS: 00010006 RAX: dffffc0000000000 RBX: 000000000001f540 RCX: 0000000000000000 RDX: 00000000c5349160 RSI: 0000000000000000 RDI: 0000000629a48b00 RBP: ffff8800a449fe88 R08: ffffffff85340730 R09: 0000000000000001 R10: 0000000000000001 R11: ffff8801bdb3c800 R12: ffff8801d017e828 R13: ffff8801d017e000 R14: 00000000d4a06480 R15: ffff8801d017e008 FS: 0000000002a13940(0063) GS:ffff8801db200000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000000 CR3: 00000000b7182000 CR4: 00000000001606f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Stack: ffff8800a449fe58 ffffffff81e75a5b ffff8801bdb3c800 ffff8801d4a06480 ffff8800b2b54800 ffff880000000001 0000000000000001 0000000000000086 000000000001f540 ffff8801d017e000 0000000000000080 dffffc0000000000 Call Trace: [] 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: 04 02 84 c0 74 08 3c 03 0f 8e da 0a 00 00 48 b8 00 00 00 00 00 fc ff df 45 8b 76 10 4a 8d 3c f5 00 67 a1 84 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 bd 0a 00 00 4a 03 1c f5 00 67 a1 84 48 89 df RIP [] try_to_wake_up+0x20b/0xf00 kernel/sched/core.c:2045 RSP ---[ end trace 8cd2c2e3ba59b7de ]---