[Bug remote/31303] New: attach calls python hooks which can crash gdb

[Bug remote/31303] New: attach calls python hooks which can crash gdb

[grazfather at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=31303

            Bug ID: 31303
           Summary: attach calls python hooks which can crash gdb
           Product: gdb
           Version: 13.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: remote
          Assignee: unassigned at sourceware dot org
          Reporter: grazfather at gmail dot com
  Target Milestone: ---

Created attachment 15337
  --> https://sourceware.org/bugzilla/attachment.cgi?id=15337&action=edit
stacktrace

On GDB 13.2, when debugging a target using `target extended-remote` with a
continue hook setup which tries to get the selected frame, when I `attach 1`,
this hook is called and gdb crashes with a failed assertion.

../../gdb/thread.c:85: internal-error: inferior_thread: Assertion
`current_thread_ != nullptr' failed.
A problem internal to GDB has been detected,

This hook does not seem to be called when I attach to a local process (by pid).

Stack trace is attached.

I reproduce with a blackmagic probe connected to a tty.

.gdbinit:

source hook_continue.py
target extended-remote /dev/cu.usbmodel72AE15F41
monitor tpwr enable
monitor swdp_scan
attach 1

hook_continue.py:

def f(_):
    gdb.selected_frame()
                                                                               
                                                    gdb.events.cont.connect(f)

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[Bug remote/31303] attach calls python hooks which can crash gdb

[grazfather at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=31303

--- Comment #1 from grazfather at gmail dot com ---
I can reproduce with `gdbserver`

root@bc1eb47da197:~/gef# gdbserver --multi localhost:1234 &
[1] 1314
root@bc1eb47da197:~/gef# Listening on port 1234
root@bc1eb47da197:~/gef# /bin/cat &
[2] 1316
root@bc1eb47da197:~/gef# gdb -q --nx --ex "source hook_attach.py" --ex "tar ext
localhost:1234" --ex "attach 1316"
attaching
Remote debugging using localhost:1234
Remote debugging from host 127.0.0.1, port 35800
Attaching to process 1316
Attached; pid = 1316
called
/build/gdb-n1n9Yr/gdb-12.1/gdb/thread.c:85: internal-error: inferior_thread:
Assertion `current_thread_ != nullptr' failed.
A problem internal to GDB has been detected,

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[Bug remote/31303] attach calls python hooks which can crash gdb

[ssbssa at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=31303

Hannes Domani <ssbssa at sourceware dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |ssbssa at sourceware dot org

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[Bug remote/31303] attach calls python hooks which can crash gdb

[grazfather at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=31303

--- Comment #2 from grazfather at gmail dot com ---
Just confirmed that this issue still exists on GDB 15.2.

❯ gdb -q --nx --ex "source hook_attach.py" --ex "tar ext x:1234" --ex "attach
1608809"Remote debugging using x:1234
Attaching to process 1608809
../../gdb/thread.c:87: internal-error: inferior_thread: Assertion
`current_thread_ != nullptr' failed.
A problem internal to GDB has been detected,
further debugging may prove unreliable.
----- Backtrace -----
---------------------
../../gdb/thread.c:87: internal-error: inferior_thread: Assertion
`current_thread_ != nullptr' failed.
A problem internal to GDB has been detected,
further debugging may prove unreliable.
Quit this debugging session? (y or n) y

This is a bug, please report it.  For instructions, see:
<https://www.gnu.org/software/gdb/bugs/>.

../../gdb/thread.c:87: internal-error: inferior_thread: Assertion
`current_thread_ != nullptr' failed.
A problem internal to GDB has been detected,
further debugging may prove unreliable.
Create a core file of GDB? (y or n) n

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[Bug remote/31303] attach calls python hooks which can crash gdb

[patryk.sondej at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=31303

Patryk Sondej <patryk.sondej at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |patryk.sondej at gmail dot com

--- Comment #3 from Patryk Sondej <patryk.sondej at gmail dot com> ---
I can confirm gdb crash.., and there is same issue for "new_thread" event.

My repro:

```
echo "gdb.events.cont.connect(lambda *args: gdb.selected_frame())" >
hook_attach.py
echo "gdb.events.new_thread.connect(lambda *args: gdb.selected_frame())" >>
hook_attach.py

gdbserver --multi localhost:1234 &
gdb -q -nx -ex "source hook_attach.py" -ex "target extended localhost:1234" -ex
"attach 1"
```

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[Bug remote/31303] attach calls python hooks which can crash gdb

[sam at gentoo dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=31303

Sam James <sam at gentoo dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           See Also|                            |https://github.com/pwndbg/p
                   |                            |wndbg/pull/3232

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[Bug remote/31303] attach calls python hooks which can crash gdb

[sam at gentoo dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=31303

Sam James <sam at gentoo dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           See Also|                            |https://github.com/pwndbg/p
                   |                            |wndbg/issues/3231

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