Re: [PATCH] Make sure GDB uses a valid shell when starting the inferior and to perform the "shell" command

Simon Marchi
2015-07-24T18:34:10Z

On 15-07-24 02:19 PM, Sergio Durigan Junior wrote:
> It is known that GDB needs a valid shell to start the inferior and to
> offer the "shell" command to the user. This has recently been the
> cause of a problem on the MIPS buildslave, because $SHELL was set to
> /sbin/nologin and several tests were failing. The thread is here:
>
> <https://sourceware.org/ml/gdb-patches/2015-07/msg00535.html>
>
> However, I think we can do better than that. If 'startup-with-shell'
> is on, which is the default, we blindly trust that the user will
> provide a valid shell for us, and this may not be true all the time.
> So I am proposing a patch to increment the tests made by GDB before
> running the inferior to decide whether it will use $SHELL or not.
> Particularly, I created a new function, called "valid_shell", which
> defines the concept of a valid shell for GDB:
>
> - A file that exists and is executable by the user
>
> - A file that is not /sbin/nologin

Note that on my Ubuntu 14.04:

$ which nologin
/usr/sbin/nologin

I think that /bin/false is also commonly specified as the default shell
for system users (at least according to my /etc/passwd).

Thanks,

Simon