[Crash-utility] [PATCH] Fixed the segment fault when ikconfig passed nonstandard values

[HAGIO KAZUHITO(萩尾 一仁)]

Hi Jackie, Hatayama san,

-----Original Message-----
> 在 2021/1/4 下午1:00, d.hatayama at fujitsu.com 写道:
> >>> Some strange reasons may cause kcore to collect some strange
> >>> entries of ikconfig, such as CONFIG_SECU+[some hex data] causes
> >> Could you tell me the example of such CONFIG_SEC+[some hex data] that
> >> causes the val to have NULL. I tried to reproduce but failed.
> 
> 
> It's hard to say about that, because It's just appeared in the virtual
> machine, when I debug
> 
> with vmcore (Not a dump.xxx file in my memory).
> 
> 
> Ubuntu-kernel/debian/rules.d/2-binary-arch.mk has that:
> 
> $(stampdir)/stamp-prepare-tree-%: $(archconfdir)/kylinos_%_defconfig
> debian/scripts/fix-filenames
>          @echo Debug: $@
>          install -d $(builddir)/build-$*
>          touch $(builddir)/build-$*/ubuntu-build
>          [ "$(do_full_source)" != 'true' ] && true || \
>                  rsync -a --exclude debian --exclude debian.master
> --exclude $(DEBIAN) * $(builddir)/build-$*
>          cat $(wordlist 1,3,$^) | sed -e
> 's/.*CONFIG_VERSION_SIGNATURE.*/CONFIG_VERSION_SIGNATURE="KYLINOS
> $(release)-$(revision)-$* $(raw_kernelversion)"/' >
> $(builddir)/build-$*/.config
>          find $(builddir)/build-$* -name "*.ko" | xargs rm -f
>          $(build_cd) $(kmake) $(build_O) -j1 olddefconfig syncconfig
> prepare scripts
>          touch $@
> 
> Every time,  '.config' has object file 'fix-filenames' hex data with
> config, maybe that is an reason, but
> 
> I'm not sure. Maybe It's just any other strange reason cause
> /proc/vmcore has CONFIG_SECU+[hex data].
> 
> > I guess you mean CONFIG_SECU+[some hex data] to be **strings that don't
> > contain the delimitor string '='** and then strtok_r() interprets
> > it as consisting of a single token, hence val resulting in having NULL.
> > If so, I think it's better to write so.

(Thanks for the comment.)

> 
> 
> Yes, It is.

Could you add more words like the above "entries that do not contain
the delimiter string '='" to the commit message?

> 
> 
> >
> > OTOH, due to the cause of this issue, is there also possibility
> > that the broken line contains two or more '=' and broken name
> > and values are appended in the ikconfig list? It has to be less
> > important than here because it doesn't result in segfault, but
> > it might be necessary to deal with it too depending on its actual impact.

Two or more '=' characters except for the first one will be added to
the value.  It can be an arbitrary string, so I think it would be hard
to check if a value is valid or not here.

If we check it, we should do when using the value.  But I don't think
the entries that crash uses can break easily..

Thanks,
Kazu