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

[Sergio Durigan Junior]

On Friday, July 24 2015, Eli Zaretskii wrote:

>> From: Sergio Durigan Junior <sergiodj@redhat.com>
>> Cc: GDB Patches <gdb-patches@sourceware.org>
>> Date: Fri, 24 Jul 2015 15:10:27 -0400
>> 
>> > Note that on my Ubuntu 14.04:
>> >
>> > $ which nologin
>> > /usr/sbin/nologin
>> 
>> /sbin/nologin is probably a symlink to this file, isn't it?  But yeah,
>> the check could include /usr/sbin/nologin as well.
>> 
>> > I think that /bin/false is also commonly specified as the default shell
>> > for system users (at least according to my /etc/passwd).
>> 
>> Indeed.  I will include /bin/false as well.
>
> Since the number of valid shells is much smaller than the number of
> non-shell programs, isn't it better to have a database of known shells
> than to have a database of non-shells people could be expected to set
> SHELL to?

My intention is not to catch all the invalid shells that can be set, but
rather make sure that the shell is at least an executable, and is not
something that is commonly used as a "non-shell", like /sbin/nologin or
/bin/false.  Other than these two I cannot think of many more options to
cover in the check.

Another good thing about doing this type of check is that every known
and unknown shell will still work.  When we explicitly check for certain
shell's as you suggest, it means that if we forget any of them its users
will be negatively impacted.

-- 
Sergio
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