================================================================== BUG: KASAN: use-after-free in l2tp_session_create+0x1439/0x1600 net/l2tp/l2tp_core.c:1854 Read of size 4 at addr ffff8880a9a9cc98 by task syz-executor.1/23633 CPU: 1 PID: 23633 Comm: syz-executor.1 Not tainted 4.14.138 #34 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+0x138/0x19c lib/dump_stack.c:53 print_address_description.cold+0x7c/0x1dc mm/kasan/report.c:252 kasan_report_error mm/kasan/report.c:351 [inline] kasan_report mm/kasan/report.c:409 [inline] kasan_report.cold+0xa9/0x2af mm/kasan/report.c:393 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:429 l2tp_session_create+0x1439/0x1600 net/l2tp/l2tp_core.c:1854 pppol2tp_connect+0x11bf/0x18b0 net/l2tp/l2tp_ppp.c:721 SYSC_connect+0x1f6/0x2d0 net/socket.c:1655 SyS_connect+0x24/0x30 net/socket.c:1636 do_syscall_64+0x1e8/0x640 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x42/0xb7 RIP: 0033:0x459829 RSP: 002b:00007f7eab127c78 EFLAGS: 00000246 ORIG_RAX: 000000000000002a RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000459829 RDX: 000000000000002e RSI: 0000000020000540 RDI: 0000000000000005 RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007f7eab1286d4 R13: 00000000004bfd8b R14: 00000000004d1b88 R15: 00000000ffffffff Allocated by task 23633: save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59 save_stack+0x45/0xd0 mm/kasan/kasan.c:447 set_track mm/kasan/kasan.c:459 [inline] kasan_kmalloc mm/kasan/kasan.c:551 [inline] kasan_kmalloc+0xce/0xf0 mm/kasan/kasan.c:529 __do_kmalloc mm/slab.c:3720 [inline] __kmalloc+0x15d/0x7a0 mm/slab.c:3729 kmalloc include/linux/slab.h:493 [inline] kzalloc include/linux/slab.h:661 [inline] l2tp_session_create+0x38/0x1600 net/l2tp/l2tp_core.c:1791 pppol2tp_connect+0x11bf/0x18b0 net/l2tp/l2tp_ppp.c:721 SYSC_connect+0x1f6/0x2d0 net/socket.c:1655 SyS_connect+0x24/0x30 net/socket.c:1636 do_syscall_64+0x1e8/0x640 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x42/0xb7 Freed by task 23635: save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59 save_stack+0x45/0xd0 mm/kasan/kasan.c:447 set_track mm/kasan/kasan.c:459 [inline] kasan_slab_free+0x75/0xc0 mm/kasan/kasan.c:524 __cache_free mm/slab.c:3496 [inline] kfree+0xcc/0x270 mm/slab.c:3815 l2tp_session_free+0x176/0x210 net/l2tp/l2tp_core.c:1714 l2tp_session_dec_refcount_1 net/l2tp/l2tp_core.h:300 [inline] l2tp_tunnel_closeall+0x2ca/0x380 net/l2tp/l2tp_core.c:1345 l2tp_udp_encap_destroy+0x99/0x100 net/l2tp/l2tp_core.c:1366 udpv6_destroy_sock+0xb3/0xd0 net/ipv6/udp.c:1444 sk_common_release+0x6b/0x310 net/core/sock.c:2984 udp_lib_close+0x16/0x20 include/net/udp.h:203 inet_release+0xec/0x1c0 net/ipv4/af_inet.c:425 inet6_release+0x53/0x80 net/ipv6/af_inet6.c:450 __sock_release+0xce/0x2b0 net/socket.c:602 sock_close+0x1b/0x30 net/socket.c:1139 __fput+0x275/0x7a0 fs/file_table.c:210 ____fput+0x16/0x20 fs/file_table.c:244 task_work_run+0x114/0x190 kernel/task_work.c:113 tracehook_notify_resume include/linux/tracehook.h:191 [inline] exit_to_usermode_loop+0x1da/0x220 arch/x86/entry/common.c:164 prepare_exit_to_usermode arch/x86/entry/common.c:199 [inline] syscall_return_slowpath arch/x86/entry/common.c:270 [inline] do_syscall_64+0x4bc/0x640 arch/x86/entry/common.c:297 entry_SYSCALL_64_after_hwframe+0x42/0xb7 The buggy address belongs to the object at ffff8880a9a9cc80 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 24 bytes inside of 512-byte region [ffff8880a9a9cc80, ffff8880a9a9ce80) The buggy address belongs to the page: page:ffffea0002a6a700 count:1 mapcount:0 mapping:ffff8880a9a9c000 index:0xffff8880a9a9c500 flags: 0x1fffc0000000100(slab) raw: 01fffc0000000100 ffff8880a9a9c000 ffff8880a9a9c500 0000000100000005 raw: ffffea0001718020 ffffea0002559ca0 ffff8880aa800940 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff8880a9a9cb80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8880a9a9cc00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffff8880a9a9cc80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff8880a9a9cd00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8880a9a9cd80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ================================================================== net_ratelimit: 23 callbacks suppressed protocol 88fb is buggy, dev hsr_slave_0 protocol 88fb is buggy, dev hsr_slave_1 protocol 88fb is buggy, dev hsr_slave_0 protocol 88fb is buggy, dev hsr_slave_1 protocol 88fb is buggy, dev hsr_slave_0 protocol 88fb is buggy, dev hsr_slave_1