Re: PROBLEM: Segfault in kconfig

From: Masahiro Yamada
Date: Sun Oct 23 2022 - 15:25:21 EST


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@xxxxxxxxxx/



Thanks.


On Thu, Oct 6, 2022 at 10:15 PM Johannes Zink <j.zink@xxxxxxxxxxxxxx> 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 |
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>


--
Best Regards
Masahiro Yamada