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From:   Masahiro Yamada <masahiroy@kernel.org>
Date:   Mon, 24 Oct 2022 04:23:39 +0900
Message-ID: <CAK7LNAThoCP3FWidnMt0h5y16VrNKKBum2NP3a=RgmaAAAdQGQ@mail.gmail.com>
Subject: Re: PROBLEM: Segfault in kconfig
To:     Johannes Zink <j.zink@pengutronix.de>
Cc:     linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org,
        kernel@pengutronix.de
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Hi Johannes,


Sorry for the delay.

I took a closer look at this.


I submitted a patch, which I think is a more correct fix.

https://patchwork.kernel.org/project/linux-kbuild/patch/20221023191055.85098-1-masahiroy@kernel.org/


Thanks.


On Thu, Oct 6, 2022 at 10:15 PM Johannes Zink <j.zink@pengutronix.de> wrote:
>
> Hi everyone,
>
> On Thu, 2022-09-22 at 18:01 +0200, Johannes Zink wrote:
> > Hi everyone,
> >
> > [1.] One line summary of the problem:
> >      kconfig crashes with segfault under rare circumstances
> > [2.] Full description of the problem/report:
> >      Under certain circumstances jump keys are displayed on the
> > search
> >      results even if a symbol is deactivated by one of its
> >      dependencies. Using the jump keys then triggers a segmentation
> >      fault due to a NULL dereference. Perform the following steps to
> >      trigger the issue
> >
> >      1.: ARCH=arm64 make defconfig
> >      2.: ARCH=arm64 make menuconfig
> >
> >      3.: press '/' key to search for the string "EFI". Use jump key
> >          (1) to jump to search result. Press 'n' key to deactivate
> > the
> >          entry.
> >      4.: press '/' to seach for the string "ACPI". Use the jump key
> >          (1) to jump to the search result.
> >
> >      Menuconfig then crashes with a segfault.
> >
> > [3.] Keywords (i.e., modules, networking, kernel):
> >      kconfig, mconf
> > [4.] Kernel information
> > [4.1.] Kernel version (from /proc/version):
> >        v6.0.0-rc6
> > [4.2.] Kernel .config file:
> >        arm64 default defconfig
> > [5.] Most recent kernel version which did not have the bug:
> >      v5.15
> > [6.] Output of Oops.. message (if applicable) with symbolic
> > information
> >      resolved (see Documentation/admin-guide/bug-hunting.rst):
> >      not applicable
> > [7.] A small shell script or example program which triggers the
> >      problem (if possible):
> >      not applicable, please see description in [2.]
> > [8.] Environment
> > [8.1.] Software (add the output of the ver_linux script here):
> >        not applicable
> > [8.2.] Processor information (from /proc/cpuinfo):
> >        not applicable
> > [8.3.] Module information (from /proc/modules):
> >        not applicable
> > [8.4.] Loaded driver and hardware information (/proc/ioports,
> > /proc/iomem):
> >        not applicable
> > [8.5.] PCI information ('lspci -vvv' as root):
> >        not applicable
> > [8.6.] SCSI information (from /proc/scsi/scsi):
> >        not applicable
> > [8.7.] Other information that might be relevant to the problem
> >        (please look in /proc and include all information that you
> >        think to be relevant):
> >        not applicable
> > [X.] Other notes, patches, fixes, workarounds:
> >
> >      I found that the attached patch is a very hacky workaround to
> >      keep menuconfig from crashing, but I am pretty sure the jump
> >      keys should not have be activated for unaccessable entries in
> > the
> >      first place. I found it quite hard to find the corresponding
> > part
> >      in mconf, which is why I decided to send this bugreport instead
> >      of sending a patch. Maybe someone on this list either knows
> > mconf
> >      really well and can just fix it, or guide me to where I can dig
> >      around (though in that case I could really use some help on how
> >      to debug menuconfig, since I found it challenging to get it
> >      working with gdb)
> >
> > Best regards
> > Johannes
> >
> > ---
> > scripts/kconfig/mconf.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/scripts/kconfig/mconf.c b/scripts/kconfig/mconf.c
> > index 9d3cf510562f..60a82f701bd3 100644
> > --- a/scripts/kconfig/mconf.c
> > +++ b/scripts/kconfig/mconf.c
> > @@ -447,7 +447,8 @@ static void search_conf(void)
> >                 again = false;
> >                 for (i = 0; i < JUMP_NB && keys[i]; i++)
> >                         if (dres == keys[i]) {
> > -                               conf(targets[i]->parent, targets[i]);
> > +                               if (targets[i]->parent)
> > +                                       conf(targets[i]->parent,
> > targets[i]);
> >                                 again = true;
> >                         }
> >                 str_free(&res);
> >
>
> Just a gentle ping and TL;DR on this issue:
>
> Menuconfig crashes with a segfault if performing the steps
>
> 1.: ARCH=arm64 make defconfig
> 2.: ARCH=arm64 make menuconfig
> 3.: press '/' key to search for the string "EFI". Use jump key
>     (1) to jump to search result. Press 'n' key to deactivate
>     the entry.
> 4.: press '/' to seach for the string "ACPI". Use the jump key
>     (1) to jump to the search result.
>
> For more details please see the detailed report in the original
> message.
>
> Has anyone any input on this?
>
> Best regards
>
> --
> Pengutronix e.K.                | Johannes Zink                  |
> Steuerwalder Str. 21            | https://www.pengutronix.de/    |
> 31137 Hildesheim, Germany       | Phone: +49-5121-206917-0       |
> Amtsgericht Hildesheim, HRA 2686| Fax:   +49-5121-206917-5555    |
>


-- 
Best Regards
Masahiro Yamada