[Bug gdb/26056] New: SIGSEGV in tui_async_resize_screen -> rl_resize_terminal on SIGWINCH with non-tty stdin/stdout

[Bug gdb/26056] New: SIGSEGV in tui_async_resize_screen -> rl_resize_terminal on SIGWINCH with non-tty stdin/stdout

[mpratt at google dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=26056

            Bug ID: 26056
           Summary: SIGSEGV in tui_async_resize_screen ->
                    rl_resize_terminal on SIGWINCH with non-tty
                    stdin/stdout
           Product: gdb
           Version: HEAD
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: gdb
          Assignee: unassigned at sourceware dot org
          Reporter: mpratt at google dot com
  Target Milestone: ---

When GDB is run with stdin == /dev/null and stdout/stderr == pipe [1] and
subsequently sent sent a SIGWINCH signal, it will crash with a SIGSEGV/SIGABRT
(depending on version).

At HEAD (specifically dcb5d41befce097d48875e744f57fe3209c61aab):

$ gdb/gdb -nx -batch -ex 'run' --args sleep 60 </dev/null 2>&1 | cat            
Python Exception <type 'exceptions.ImportError'> No module named gdb:  
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.
zsh: abort      gdb/gdb -nx -batch -ex 'run' --args sleep 60 < /dev/null 2>&1 | 
zsh: done       cat 

While running:
$ pkill -WINCH gdb

The crashing stack is:

(gdb) bt
#0  __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:50
#1  0x00007f3e39c4b55b in __GI_abort () at abort.c:79
#2  0x000055d51f121260 in handle_sigsegv (sig=11) at event-top.c:885
#3  <signal handler called>
#4  __GI___fileno (fp=0x0) at fileno.c:35
#5  0x000055d51f4964a0 in rl_resize_terminal () at terminal.c:368
#6  0x000055d51f44117b in tui_async_resize_screen (arg=<optimized out>) at
tui/tui-win.c:541
#7  0x000055d51f171a02 in invoke_async_signal_handlers () at async-event.c:206
#8  0x000055d51f5581ae in gdb_do_one_event () at event-loop.cc:172
#9  0x000055d51f41ef9c in wait_sync_command_done () at top.c:526
#10 0x000055d51f41f435 in maybe_wait_sync_command_done (was_sync=0) at
top.c:543
#11 execute_command (p=<optimized out>, p@entry=<error reading variable: value
has been optimized out>, from_tty=<error reading variable: value has been
optimized out>) at top.c:657
#12 0x000055d51f3042f0 in catch_command_errors (command=<optimized out>,
arg=<optimized out>, from_tty=<optimized out>) at main.c:457
#13 0x000055d51f3058d9 in captured_main_1 (context=<optimized out>) at
main.c:1219
#14 0x000055d51f30615b in captured_main (data=<optimized out>) at main.c:1269
#15 gdb_main (args=<optimized out>) at main.c:1269
#16 0x000055d51f13750c in main (argc=<optimized out>, argv=<optimized out>) at
gdb.c:32

With my system GDB (Debian 8.3.1-1):

$ gdb -nx -batch -ex 'run' --args sleep 60 </dev/null 2>&1 | cat    
zsh: segmentation fault  gdb -nx -batch -ex 'run' --args sleep 60 < /dev/null
2>&1 | 
zsh: done                cat

The crashing stack is the same, there is just no SIGSEGV handler that
translates the SIGSEGV to SIGABRT.

I've seen this crash on HEAD, 8.3, 8.2, 8.1, and 7.12.

This bug was discovered when investigating flaky GDB integration tests in the
Go project: https://github.com/golang/go/issues/39021. Those tests use the Go
os/exec.Command.CombinedOutput() stdlib function (same Go code:
https://github.com/golang/go/issues/39021#issuecomment-634919443). This
function runs the subprocess with stdin set to /dev/null and stdout and stderr
set to a pipe.

As I understand it, the immediate problem is that rl_resize_terminal is
expected to crash when rl_initialize has not been called. In some
non-interactive cases (not sure of the exact behavior), GDB doesn't call
rl_initialize because it is "unnecessary". Yet, it still installs the
tui_async_resize_screen SIGWINCH handler, which unconditionally calls
rl_resize_terminal.

In addition to a fix, I've been looking for a good workaround to convince GDB
not to crash.

[1] I believe a more common set of non-tty I/O will trigger this bug, but these
are the specific inputs I've used to reproduce the issue.

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[Bug gdb/26056] SIGSEGV in tui_async_resize_screen -> rl_resize_terminal on SIGWINCH with non-tty stdin/stdout

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=26056

Tom Tromey <tromey at sourceware dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |WAITING
   Last reconfirmed|                            |2020-08-09
     Ever confirmed|0                           |1
                 CC|                            |tromey at sourceware dot org

--- Comment #1 from Tom Tromey <tromey at sourceware dot org> ---
FWIW this seems to work ok with git gdb.
There have been many TUI changes since 8.3, including in
the readline initialization area.

Could you try git gdb and see if it works?

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[Bug gdb/26056] SIGSEGV in tui_async_resize_screen -> rl_resize_terminal on SIGWINCH with non-tty stdin/stdout

[mpratt at google dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=26056

--- Comment #2 from Michael Pratt <mpratt at google dot com> ---
I'm still seeing the same behavior at 3eb651743e06fb360687a26be87bc6b710fc7066
("Implement missing powerpc mtspr and mfspr extended insns").

$ gdb/gdb -nx -batch -ex 'run' --args sleep 60 </dev/null 2>&1 | cat
Python Exception <type 'exceptions.ImportError'> No module named gdb:
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. 
zsh: abort      gdb/gdb -nx -batch -ex 'run' --args sleep 60 < /dev/null 2>&1 |
zsh: done       cat   

$ pkill -WINCH gdb

Same crash location:

(top-gdb) bt
#0  __GI___fileno (fp=0x0) at fileno.c:35
#1  0x000055d06e689d40 in rl_resize_terminal () at terminal.c:368
#2  0x000055d06e634c0b in tui_async_resize_screen (arg=<optimized out>) at
tui/tui-win.c:541
#3  0x000055d06e358ee2 in invoke_async_signal_handlers () at async-event.c:206
#4  0x000055d06e751e4e in gdb_do_one_event () at event-loop.cc:172
#5  0x000055d06e6126cc in wait_sync_command_done () at top.c:526
#6  0x000055d06e612e32 in maybe_wait_sync_command_done (was_sync=0) at
top.c:543
#7  execute_command (p=<optimized out>, p@entry=<error reading variable: value
has been optimized out>, from_tty=<error reading variable: value has been
optimized out>) at top.c:670
#8  0x000055d06e4f3b50 in catch_command_errors (command=<optimized out>,
arg=<optimized out>, from_tty=<optimized out>) at main.c:457
#9  0x000055d06e4f5119 in captured_main_1 (context=<optimized out>) at
main.c:1218
#10 0x000055d06e4f59bb in captured_main (data=<optimized out>) at main.c:1268
#11 gdb_main (args=<optimized out>) at main.c:1268
#12 0x000055d06e31dd9c in main (argc=<optimized out>, argv=<optimized out>) at
gdb.c:32

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[Bug gdb/26056] SIGSEGV in tui_async_resize_screen -> rl_resize_terminal on SIGWINCH with non-tty stdin/stdout

[anudeephomes247 at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=26056

anudeep homes247 <anudeephomes247 at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |anudeephomes247 at gmail dot com

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[Bug gdb/26056] SIGSEGV in tui_async_resize_screen -> rl_resize_terminal on SIGWINCH with non-tty stdin/stdout

[mark at klomp dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=26056

Mark Wielaard <mark at klomp dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mark at klomp dot org

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[Bug gdb/26056] SIGSEGV in tui_async_resize_screen -> rl_resize_terminal on SIGWINCH with non-tty stdin/stdout

[tulzakasi at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=26056

godrejanandabagalur <tulzakasi at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |tulzakasi at gmail dot com

--- Comment #4 from godrejanandabagalur <tulzakasi at gmail dot com> ---
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[Bug gdb/26056] SIGSEGV in tui_async_resize_screen -> rl_resize_terminal on SIGWINCH with non-tty stdin/stdout

[ashish.lumar2902 at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=26056

Alex Sam <ashish.lumar2902 at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |ashish.lumar2902 at gmail dot com

--- Comment #5 from Alex Sam <ashish.lumar2902 at gmail dot com> ---
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[Bug gdb/26056] SIGSEGV in tui_async_resize_screen -> rl_resize_terminal on SIGWINCH with non-tty stdin/stdout

[lsix at lancelotsix dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=26056

Lancelot SIX <lsix at lancelotsix dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |lsix at lancelotsix dot com
             Status|WAITING                     |RESOLVED
         Resolution|---                         |FIXED

--- Comment #6 from Lancelot SIX <lsix at lancelotsix dot com> ---
Fixed in commit 72994b6028360eccb5d25b39d2e18b386d091426.

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