kobject: 'loop0' (ffff880125cecf20): kobject_uevent_env kobject: 'loop0' (ffff880125cecf20): fill_kobj_path: path = '/devices/virtual/block/loop0' gretap0: Invalid MTU 47872 requested, hw max 1500 refcount_t: underflow; use-after-free. ------------[ cut here ]------------ WARNING: CPU: 1 PID: 6968 at lib/refcount.c:184 refcount_sub_and_test+0x11b/0x170 lib/refcount.c:184 Kernel panic - not syncing: panic_on_warn set ... CPU: 1 PID: 6968 Comm: syz-executor.0 Not tainted 4.12.0-rc7-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:16 [inline] dump_stack+0x145/0x1f1 lib/dump_stack.c:52 panic+0x1b6/0x358 kernel/panic.c:180 __warn+0x18d/0x1b0 kernel/panic.c:541 report_bug+0x1a4/0x250 lib/bug.c:183 fixup_bug.part.15+0x37/0x80 arch/x86/kernel/traps.c:190 fixup_bug arch/x86/kernel/traps.c:187 [inline] do_trap_no_signal arch/x86/kernel/traps.c:224 [inline] do_trap+0x77/0x340 arch/x86/kernel/traps.c:273 do_error_trap+0x120/0x390 arch/x86/kernel/traps.c:310 do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:323 invalid_op+0x1e/0x30 arch/x86/entry/entry_64.S:844 RIP: 0010:refcount_sub_and_test+0x11b/0x170 lib/refcount.c:184 RSP: 0018:ffff8801168feba8 EFLAGS: 00010286 RAX: 0000000000000026 RBX: 1ffff10022d1fd77 RCX: 0000000000000000 RDX: 0000000000000026 RSI: 1ffff100207b855e RDI: ffffed0022d1fd6b RBP: ffff8801168fec38 R08: 1ffff10022d1fd0f R09: 0000000000000000 R10: ffff8801168fe610 R11: 0000000000000000 R12: 1ffff10022d1fd7b R13: 0000000000000100 R14: ffff8801168fec18 R15: ffff88011d421080 sctp_wfree+0x185/0x5e0 net/sctp/socket.c:7745 skb_release_head_state+0xf3/0x1e0 net/core/skbuff.c:652 skb_release_all+0xd/0x50 net/core/skbuff.c:665 __kfree_skb net/core/skbuff.c:681 [inline] consume_skb+0x135/0x460 net/core/skbuff.c:748 sctp_chunk_destroy net/sctp/sm_make_chunk.c:1441 [inline] sctp_chunk_put+0x26c/0x3d0 net/sctp/sm_make_chunk.c:1468 sctp_datamsg_destroy net/sctp/chunk.c:129 [inline] sctp_datamsg_put+0x1f9/0x5a0 net/sctp/chunk.c:146 sctp_chunk_free+0x37/0x50 net/sctp/sm_make_chunk.c:1453 __sctp_outq_teardown+0x25c/0x1670 net/sctp/outqueue.c:228 sctp_outq_free+0x9/0x10 net/sctp/outqueue.c:284 sctp_association_free+0x2ab/0x8b0 net/sctp/associola.c:358 sctp_cmd_delete_tcb net/sctp/sm_sideeffect.c:917 [inline] sctp_cmd_interpreter net/sctp/sm_sideeffect.c:1333 [inline] sctp_side_effects net/sctp/sm_sideeffect.c:1198 [inline] sctp_do_sm+0x230d/0x6a10 net/sctp/sm_sideeffect.c:1170 sctp_primitive_ABORT+0x7c/0xc0 net/sctp/primitive.c:119 sctp_close+0x268/0x9a0 net/sctp/socket.c:1529 inet_release+0xd9/0x1c0 net/ipv4/af_inet.c:425 sock_release+0x83/0x1b0 net/socket.c:597 sock_close+0xd/0x20 net/socket.c:1113 __fput+0x307/0x900 fs/file_table.c:209 ____fput+0x9/0x10 fs/file_table.c:245 task_work_run+0x140/0x220 kernel/task_work.c:116 tracehook_notify_resume include/linux/tracehook.h:191 [inline] exit_to_usermode_loop+0x221/0x2a0 arch/x86/entry/common.c:161 prepare_exit_to_usermode arch/x86/entry/common.c:194 [inline] syscall_return_slowpath+0x344/0x3f0 arch/x86/entry/common.c:263 entry_SYSCALL_64_fastpath+0xc0/0xc2 RIP: 0033:0x4141d1 RSP: 002b:00007ffc1f90a950 EFLAGS: 00000293 ORIG_RAX: 0000000000000003 RAX: 0000000000000000 RBX: 0000000000000007 RCX: 00000000004141d1 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000006 RBP: 0000000000000001 R08: ffffffffffffffff R09: ffffffffffffffff R10: 00007ffc1f90aa30 R11: 0000000000000293 R12: 000000000075bf20 R13: 000000000000fcd7 R14: 0000000000761400 R15: 000000000075bf2c Kernel Offset: disabled Rebooting in 86400 seconds..