Re: bash-4-2 issue

[Grisha Levit]

On Mon, Jan 8, 2024 at 7:04 AM Sam Kappen via Bug reports for the GNU
Bourne Again SHell <bug-bash@gnu.org> wrote:
> We see that bash throws the "Operation not permitted" error when doing
> chained pipe operation
> along with a debug trap.
>
> We set a debug trap here "my_debug" to save the terminal commands entered.
> The GNU bash, version used is  4.2.
>
> root@freescale-p2020ds:~/dir#  ls -l | grep a | grep b | grep c
> -sh: child setpgid (4238 to 4232): Operation not permitted
>
>
> root@freescale-p2020ds:~/dir# trap
> trap -- '' TSTP
> trap -- '' TTIN
> trap -- '' TTOU
> trap -- 'my_debug' DEBUG
> root@freescale-p2020ds:~/dir#
>
> Platform: Linux 3.10 kernel on PPC target.
>
> It seems setpgid is failing because the process group of the pipeline does
> not exist at that time.
>
> This issue is not seen on bash version 4.4.

I'm not sure this is fixed. In all versions, including 4.2, 4.4, 5.2, and the
current devel version, I see what seems to be the same error, triggered by a
pipeline when job control is enabled and the DEBUG trap executes an external
command.

    $ bash -m -c 'trap /usr/bin/true DEBUG; :|:'
    bash: child setpgid (49581 to 49579): Operation not permitted

And an accompanying warning if Bash is built with -DDEBUG:

    DEBUG warning: delete_job (0 pgrp 49579): js.c_reaped (-1) < 0
ndel = 2 js.j_ndead = 0

> I am looking to figure out the particular fix that fixed this issue from
> the above commit and to backport to bash4-2 version.

In general you want to bisect using commits in the devel branch:
https://git.savannah.gnu.org/cgit/bash.git/log/?h=devel