================================================================== BUG: KASAN: use-after-free in l2tp_session_create+0xa6d/0xc60 net/l2tp/l2tp_core.c:1757 Read of size 4 at addr ffff8801b7159368 by task syz-executor6/15352 CPU: 1 PID: 15352 Comm: syz-executor6 Not tainted 4.15.0+ #287 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0x194/0x257 lib/dump_stack.c:53 print_address_description+0x73/0x250 mm/kasan/report.c:252 kasan_report_error mm/kasan/report.c:351 [inline] kasan_report+0x25b/0x340 mm/kasan/report.c:409 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:429 l2tp_session_create+0xa6d/0xc60 net/l2tp/l2tp_core.c:1757 pppol2tp_connect+0xed7/0x1dd0 net/l2tp/l2tp_ppp.c:748 SYSC_connect+0x213/0x4a0 net/socket.c:1621 SyS_connect+0x24/0x30 net/socket.c:1602 entry_SYSCALL_64_fastpath+0x29/0xa0 RIP: 0033:0x453299 RSP: 002b:00007f836166bc58 EFLAGS: 00000212 ORIG_RAX: 000000000000002a RAX: ffffffffffffffda RBX: 000000000071bea0 RCX: 0000000000453299 RDX: 000000000000002e RSI: 00000000205fafd2 RDI: 0000000000000018 RBP: 00000000000005d5 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006f7c98 R13: 00000000ffffffff R14: 00007f836166c6d4 R15: 0000000000000000 Allocated by task 15352: save_stack+0x43/0xd0 mm/kasan/kasan.c:447 set_track mm/kasan/kasan.c:459 [inline] kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:551 kmem_cache_alloc_trace+0x136/0x750 mm/slab.c:3610 kmalloc include/linux/slab.h:499 [inline] kzalloc include/linux/slab.h:688 [inline] l2tp_tunnel_create+0x5e1/0x17f0 net/l2tp/l2tp_core.c:1554 pppol2tp_connect+0x14b7/0x1dd0 net/l2tp/l2tp_ppp.c:707 SYSC_connect+0x213/0x4a0 net/socket.c:1621 SyS_connect+0x24/0x30 net/socket.c:1602 entry_SYSCALL_64_fastpath+0x29/0xa0 Freed by task 4168: save_stack+0x43/0xd0 mm/kasan/kasan.c:447 set_track mm/kasan/kasan.c:459 [inline] kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524 __cache_free mm/slab.c:3488 [inline] kfree+0xd6/0x260 mm/slab.c:3803 __rcu_reclaim kernel/rcu/rcu.h:167 [inline] rcu_do_batch kernel/rcu/tree.c:2674 [inline] invoke_rcu_callbacks kernel/rcu/tree.c:2933 [inline] __rcu_process_callbacks kernel/rcu/tree.c:2900 [inline] rcu_process_callbacks+0xe94/0x17f0 kernel/rcu/tree.c:2917 __do_softirq+0x2d7/0xb85 kernel/softirq.c:285 The buggy address belongs to the object at ffff8801b7159280 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 232 bytes inside of 512-byte region [ffff8801b7159280, ffff8801b7159480) The buggy address belongs to the page: page:ffffea0006dc5640 count:1 mapcount:0 mapping:ffff8801b7159000 index:0x0 flags: 0x2fffc0000000100(slab) raw: 02fffc0000000100 ffff8801b7159000 0000000000000000 0000000100000006 raw: ffffea0006d38160 ffffea0006d36020 ffff8801db000940 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff8801b7159200: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff8801b7159280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff8801b7159300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff8801b7159380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8801b7159400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ==================================================================