linux-kernel - Re: [PATCH 2/2] kconfig/nconf: prevent segfault on empty menu

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Date:	Mon, 11 Jul 2011 10:51:30 +0200
From:	Andrej Gelenberg <andrej.gelenberg@....edu>
To:	Nir Tzachar <nir.tzachar@...il.com>, linux-kbuild@...r.kernel.org,
	mmarek@...e.cz, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] kconfig/nconf: prevent segfault on empty menu

Hello,

it show already "There is no help available for this option." message on
F2. Only caption could be better as just "(null)". Besides ignore the
key is much better as segfault.

Regards,
Andrej Gelenberg

On 07/10/2011 12:32 PM, Nir Tzachar wrote:
> Hello.
> 
> On Sun, Jul 10, 2011 at 10:27 AM, Arnaud Lacombe <lacombar@...il.com> wrote:
>> nconf does not check the validity of the current menu when help is requested
>> (with either <F2>, '?' or 'h'). This leads to a NULL pointer dereference when an
>> empty menu is encountered.
>>
>> The following reduced testcase exposes the problem:
>>
>> config DEP
>>        bool
>>
>> menu "FOO"
>>
>> config BAR
>>        bool "BAR"
>>        depends on DEP
>>
>> endmenu
>>
>> Issue will happen when entering menu "FOO" and requesting help.
>>
>> nconf is the only front-end which do not filter the validity of the current
>> menu. Such filter can not really happen beforehand as other key which does not
>> deals with the current menu might be entered by the user, so just bails out
>> earlier if we encounter an invalid menu.
> 
> I do not believe the correct solution is silently ignoring the user's
> key presses. I think the correct behavior would be to display a
> nohelp_text window.
> 
> something like this (untested):
> show_scroll_win(main_window, nohelp_text);
> 
> The other patches in the series seem gr8.
> 
> Cheers.
> 
>> Cc: Nir Tzachar <nir.tzachar@...il.com>
>> Cc: Andrej Gelenberg <andrej.gelenberg@....edu>
>> Reported-by: Andrej Gelenberg <andrej.gelenberg@....edu>
>> Signed-off-by: Arnaud Lacombe <lacombar@...il.com>
>> ---
>>  scripts/kconfig/nconf.c |    7 ++++++-
>>  1 files changed, 6 insertions(+), 1 deletions(-)
>>
>> diff --git a/scripts/kconfig/nconf.c b/scripts/kconfig/nconf.c
>> index 24fc79a..eb9e49d 100644
>> --- a/scripts/kconfig/nconf.c
>> +++ b/scripts/kconfig/nconf.c
>> @@ -1222,7 +1222,12 @@ static void conf_message_callback(const char *fmt, va_list ap)
>>
>>  static void show_help(struct menu *menu)
>>  {
>> -       struct gstr help = str_new();
>> +       struct gstr help;
>> +
>> +       if (!menu)
>> +               return;
>> +
>> +       help = str_new();
>>        menu_get_ext_help(menu, &help);
>>        show_scroll_win(main_window, _(menu_get_prompt(menu)), str_get(&help));
>>        str_free(&help);
>> --
>> 1.7.3.4.574.g608b.dirty
>>
>>

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