Hello, syzbot found the following crash on: HEAD commit: bee46b30 Add linux-next specific files for 20200221 git tree: linux-next console output: https://syzkaller.appspot.com/x/log.txt?x=1244ea7ee00000 kernel config: https://syzkaller.appspot.com/x/.config?x=10693880b4976691 dashboard link: https://syzkaller.appspot.com/bug?extid=198362c76088d1515529 compiler: gcc (GCC) 9.0.0 20181231 (experimental) syz repro: https://syzkaller.appspot.com/x/repro.syz?x=160a03d9e00000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=10f8e1dde00000 Bisection is inconclusive: the bug happens on the oldest tested release. bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=13f03a7ee00000 final crash: https://syzkaller.appspot.com/x/report.txt?x=10083a7ee00000 console output: https://syzkaller.appspot.com/x/log.txt?x=17f03a7ee00000 IMPORTANT: if you fix the bug, please add the following tag to the commit: Reported-by: syzbot+198362c76088d1515529@xxxxxxxxxxxxxxxxxxxxxxxxx ------------[ cut here ]------------ refcount_t: underflow; use-after-free. WARNING: CPU: 1 PID: 2940 at lib/refcount.c:28 refcount_warn_saturate+0x1dc/0x1f0 lib/refcount.c:28 Kernel panic - not syncing: panic_on_warn set ... CPU: 1 PID: 2940 Comm: kworker/1:12 Not tainted 5.6.0-rc2-next-20200221-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: events do_enable_set Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x197/0x210 lib/dump_stack.c:118 panic+0x2e3/0x75c kernel/panic.c:221 __warn.cold+0x2f/0x3e kernel/panic.c:582 report_bug+0x289/0x300 lib/bug.c:195 fixup_bug arch/x86/kernel/traps.c:175 [inline] fixup_bug arch/x86/kernel/traps.c:170 [inline] do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:267 do_invalid_op+0x37/0x50 arch/x86/kernel/traps.c:286 invalid_op+0x23/0x30 arch/x86/entry/entry_64.S:1027 RIP: 0010:refcount_warn_saturate+0x1dc/0x1f0 lib/refcount.c:28 Code: e9 d8 fe ff ff 48 89 df e8 81 81 10 fe e9 85 fe ff ff e8 07 54 d1 fd 48 c7 c7 00 c8 91 88 c6 05 6b f6 fc 06 01 e8 23 74 a1 fd <0f> 0b e9 ac fe ff ff 0f 1f 00 66 2e 0f 1f 84 00 00 00 00 00 55 48 RSP: 0018:ffffc9000952fbd8 EFLAGS: 00010286 RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000 RDX: 0000000000000000 RSI: ffffffff815ee766 RDI: fffff520012a5f6d RBP: ffffc9000952fbe8 R08: ffff88809e82e600 R09: ffffed1015d26661 R10: ffffed1015d26660 R11: ffff8880ae933307 R12: 0000000000000003 R13: ffff888095b3f018 R14: dead000000000122 R15: ffffc9000952fc98 refcount_sub_and_test include/linux/refcount.h:261 [inline] refcount_dec_and_test include/linux/refcount.h:281 [inline] kref_put include/linux/kref.h:64 [inline] l2cap_chan_put+0x1d9/0x240 net/bluetooth/l2cap_core.c:501 do_enable_set+0x54b/0x960 net/bluetooth/6lowpan.c:1075 process_one_work+0xa05/0x17a0 kernel/workqueue.c:2266 worker_thread+0x98/0xe40 kernel/workqueue.c:2412 kthread+0x361/0x430 kernel/kthread.c:255 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352 Kernel Offset: disabled Rebooting in 86400 seconds.. --- This bug is generated by a bot. It may contain errors. See https://goo.gl/tpsmEJ for more information about syzbot. syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx. syzbot will keep track of this bug report. See: https://goo.gl/tpsmEJ#status for how to communicate with syzbot. For information about bisection process see: https://goo.gl/tpsmEJ#bisection syzbot can test patches for this bug, for details see: https://goo.gl/tpsmEJ#testing-patches
