This is the mail archive of the
gdb-patches@sourceware.org
mailing list for the GDB project.
Re: [patch] segmentation fault at gdbserver
- From: Liang Cheng <liang dot cheng555 at gmail dot com>
- To: gdb-patches at sourceware dot org
- Cc: pedro at codesourcery dot com
- Date: Mon, 27 Jun 2011 12:18:11 -0500
- Subject: Re: [patch] segmentation fault at gdbserver
- References: <BANLkTim6=jeGyYoHBBy=jM5n0tFj2obnNA@mail.gmail.com>
Hi Pedro,
Can you please review this change?
thanks
Liang
2011-06-27 Liang Cheng <liang.cheng555@gmail.com>
* tracepoint.c (cmd_qtstatus): Check whether current_inferior is NULL.
--- tracepoint.c.orig 2011-05-12 07:09:18.000000000 -0500
+++ tracepoint.c 2011-06-22 14:05:13.553993630 -0500
@@ -3159,7 +3159,7 @@
trace_debug ("Returning trace status as %d, stop reason %s",
tracing, tracing_stop_reason);
- if (in_process_agent_loaded ())
+ if (in_process_agent_loaded () && current_inferior != NULL)
{
pause_all (1);
On Fri, Jun 24, 2011 at 5:15 PM, Liang Cheng <liang.cheng555@gmail.com> wrote:
> The repro step is:
> 1. compile and link the test app (which contains an infinite loop)
> against libinproctrace.so
> 2. run the app
> 3. start gdbserver in multiprocess mode (e.g. gdbserver --multi :5040)
> 3. attach the running process in gdb
> 4. detach
> 5. quit
>
> Note: I did not setup any tracepoints during the experiment.
> But at step 5, gdbserver will get segmentation fault. The
> segmentation fault is caused by de-referencing a null pointer
> variable: *current_inferior*. But this issue may be exposed as well
> even you have tracepoints setup.
>
> The two commands "detach" and "quit" at gdb side would issue
> *remote_get_trace_status* function call respectively in the
> form of "qTStatus". In the handle of gdbserver side for this
> event gdbserver/tracepoint.c::cmd_qtstatus calls
> upload_fast_traceframes() in case the libinproctrace.so is loaded.
> Upload_fast_traceframes() eventually references the *current_inferior*
> , which is null at the 2nd call of cmd_qtstatus.
>
> Current_inferior is set to NULL at gdbserver after receiving *detach*.
> (server.c:2751). So at the time of "quit", the pointer is already NULL.
>
> OK to apply the patch below?
>
> Thanks
> Liang
>
> --- tracepoint.c.orig ? 2011-05-12 07:09:18.000000000 -0500
> +++ tracepoint.c ? ? ? ?2011-06-22 14:05:13.553993630 -0500
> @@ -3159,7 +3159,7 @@
> ? trace_debug ("Returning trace status as %d, stop reason %s",
> ? ? ? ? ? ? ? tracing, tracing_stop_reason);
>
> - ?if (in_process_agent_loaded ())
> + ?if (in_process_agent_loaded () && current_inferior != NULL)
> ? ? {
> ? ? ? pause_all (1);
>