Re: WARNING in tracepoint_probe_register_prio (2)

[Mathieu Desnoyers]

----- On Mar 12, 2018, at 9:59 PM, syzbot syzbot+9c0d616860575a73166a@xxxxxxxxxxxxxxxxxxxxxxxxx wrote:

> Hello,
> 
> syzbot hit the following crash on bpf-next commit
> 6d8cb045cde681e64a5ed80a2ab70be831a7f9b0 (Fri Mar 9 07:46:33 2018 +0000)
> bpf: comment why dots in filenames under BPF virtual FS are not allowed

Hi,

Here is a WARN_ON() splat in tracepoint.c, which I suspect is caused
by perf trying to register the same probe twice to the tracepoint API.
We got another splat on unregister too, which I will forward in a
separate email.

Thoughts ?

Thanks,

Mathieu


> 
> So far this crash happened 6 times on bpf-next, upstream.
> C reproducer is attached.
> syzkaller reproducer is attached.
> Raw console output is attached.
> compiler: gcc (GCC) 7.1.1 20170620
> .config is attached.
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+9c0d616860575a73166a@xxxxxxxxxxxxxxxxxxxxxxxxx
> It will help syzbot understand when the bug is fixed. See footer for
> details.
> If you forward the report, please keep this part and the footer.
> 
> RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000441dd9
> RDX: 00000000ffffffff RSI: 0000000000000000 RDI: 0000000020348f88
> RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000032
> R10: 0000000000000003 R11: 0000000000000246 R12: 0000000000000004
> R13: ffffffffffffffff R14: 0000000000000000 R15: 0000000000000000
> WARNING: CPU: 0 PID: 4185 at kernel/tracepoint.c:210 tracepoint_add_func
> kernel/tracepoint.c:210 [inline]
> WARNING: CPU: 0 PID: 4185 at kernel/tracepoint.c:210
> tracepoint_probe_register_prio+0x397/0x9a0 kernel/tracepoint.c:282
> Kernel panic - not syncing: panic_on_warn set ...
> 
> CPU: 0 PID: 4185 Comm: syzkaller994063 Not tainted 4.16.0-rc4+ #28
> 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+0x194/0x24d lib/dump_stack.c:53
>  panic+0x1e4/0x41c kernel/panic.c:183
>  __warn+0x1dc/0x200 kernel/panic.c:547
>  report_bug+0x211/0x2d0 lib/bug.c:184
>  fixup_bug.part.11+0x37/0x80 arch/x86/kernel/traps.c:178
>  fixup_bug arch/x86/kernel/traps.c:247 [inline]
>  do_error_trap+0x2d7/0x3e0 arch/x86/kernel/traps.c:296
>  do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:315
>  invalid_op+0x1b/0x40 arch/x86/entry/entry_64.S:986
> RIP: 0010:tracepoint_add_func kernel/tracepoint.c:210 [inline]
> RIP: 0010:tracepoint_probe_register_prio+0x397/0x9a0 kernel/tracepoint.c:282
> RSP: 0018:ffff8801bbc87468 EFLAGS: 00010293
> RAX: ffff8801b5a3c680 RBX: 00000000fffffff4 RCX: ffffffff81735e67
> RDX: 0000000000000000 RSI: ffffffff86f42a00 RDI: 0000000000000286
> RBP: ffff8801bbc87570 R08: 1ffff10037790de1 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
> R13: dffffc0000000000 R14: 0000000000000000 R15: ffff8801bbc87548
>  tracepoint_probe_register+0x2a/0x40 kernel/tracepoint.c:303
>  trace_event_reg+0x167/0x320 kernel/trace/trace_events.c:305
>  perf_trace_event_reg kernel/trace/trace_event_perf.c:122 [inline]
>  perf_trace_event_init kernel/trace/trace_event_perf.c:197 [inline]
>  perf_trace_init+0x4ef/0xab0 kernel/trace/trace_event_perf.c:221
>  perf_tp_event_init+0x7d/0xf0 kernel/events/core.c:7979
>  perf_try_init_event+0xc9/0x2a0 kernel/events/core.c:9240
>  perf_init_event kernel/events/core.c:9278 [inline]
>  perf_event_alloc+0x1cc6/0x2b00 kernel/events/core.c:9542
>  SYSC_perf_event_open+0x84e/0x2e00 kernel/events/core.c:9997
>  SyS_perf_event_open+0x39/0x50 kernel/events/core.c:9883
>  do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
>  entry_SYSCALL_64_after_hwframe+0x42/0xb7
> RIP: 0033:0x441dd9
> RSP: 002b:00007ffcca452388 EFLAGS: 00000246 ORIG_RAX: 000000000000012a
> RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000441dd9
> RDX: 00000000ffffffff RSI: 0000000000000000 RDI: 0000000020348f88
> RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000032
> R10: 0000000000000003 R11: 0000000000000246 R12: 0000000000000004
> R13: ffffffffffffffff R14: 0000000000000000 R15: 0000000000000000
> Dumping ftrace buffer:
>    (ftrace buffer empty)
> Kernel Offset: disabled
> Rebooting in 86400 seconds..
> 
> 
> ---
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-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com