[Bug gdb/22995] New: crash when backtrace includes a removed shared object

["etesta at undo dot io" <sourceware-bugzilla at sourceware dot org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=22995

            Bug ID: 22995
           Summary: crash when backtrace includes a removed shared object
           Product: gdb
           Version: 8.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: gdb
          Assignee: unassigned at sourceware dot org
          Reporter: etesta at undo dot io
  Target Milestone: ---

Created attachment 10910
  --> https://sourceware.org/bugzilla/attachment.cgi?id=10910&action=edit
Reproducer for the issue.

I am using gdb-8.1 and I have a test (attached) that makes GDB crash under the
following scenario:

1) compile the test:

$ gcc -o test5085 test5085.c -ldl
$ gcc -c -fpic test5085_lib.c
$ gcc -shared -o test5085_64_lib.so test5085_lib.o

then load it in gdb:

$ gdb test5085

and...

Python Exception <type 'exceptions.ImportError'> No module named gdb:
/home/etesta/tmp/gdb81_build/gdb/gdb: warning:
Could not load the Python gdb module from `/usr/local/share/gdb/python'.
Limited Python support is available from the _gdb module.
Suggest passing --data-directory=/path/to/gdb/data-directory.

GNU gdb (GDB) 8.1
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There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-pc-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
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For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from ./test5085...(no debugging symbols found)...done.

(gdb) break dlsym

Breakpoint 1 at 0x4005e0

(gdb) r ./test5085_64_lib.so

Starting program: /home/etesta/tmp/test5085/test5085 ./test5085_64_lib.so

Breakpoint 1, Python Exception <type 'exceptions.NameError'> Installation
error: gdb.execute_unwinders function is missing:
0x00007ffff7bd4040 in dlsym () from /lib/x86_64-linux-gnu/libdl.so.2


AT THIS POINT REMOVE OR MOVE test5058_64_lib.so

(gdb) c

Continuing.

Program received signal SIGSEGV, Segmentation fault.
Python Exception <type 'exceptions.NameError'> Installation error:
gdb.execute_unwinders function is missing:
BFD: reopening ./test5085_64_lib.so: No such file or directory

BFD: reopening ./test5085_64_lib.so: No such file or directory

(gdb) bt

Segmentation fault (core dumped)

I did a bit of investigation and I noticed that with this issue was already
reported a while back and it was fixed with:

commit 938f0e2f6766e90a5ddc5df00e97a68873fd1252
Author: Andrew Burgess <aburgess@broadcom.com>
Date:   Wed Apr 2 17:02:51 2014 +0100

   Remove previous frame if an error occurs when computing frame id during
unwind.

but then broken by:

commit f245535cf583ae4ca13b10d47b3c7d3334593ece
Author: Pedro Alves <palves@redhat.com>
Date:   Mon Sep 5 18:41:38 2016 +0100

    Fix PR19927: Avoid unwinder recursion if sniffer uses calls parse_and_eval

I keep getting a build failure with the latest git commit on master, so I
didn't try with the latest code.

I am available should you need any more information.

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