Re: [PATCH] sh: Fix build with CONFIG_UBSAN=y

[Kees Cook]

On Wed, Jan 31, 2024 at 12:19:22PM +0100, John Paul Adrian Glaubitz wrote:
> Hi Kees,
> 
> On Wed, 2024-01-31 at 12:03 +0100, John Paul Adrian Glaubitz wrote:
> > Hi Kees,
> > 
> > On Tue, 2024-01-30 at 15:27 -0800, Kees Cook wrote:
> > > The early boot stub for sh had UBSan instrumentation present where it is
> > > not supported. Disable it for this part of the build.
> > > 
> > >   sh4-linux-ld: arch/sh/boot/compressed/misc.o: in function `zlib_inflate_table':
> > >   misc.c:(.text+0x670): undefined reference to `__ubsan_handle_shift_out_of_bounds'
> > > 
> > > Reported-by: kernel test robot <lkp@xxxxxxxxx>
> > > Closes: https://lore.kernel.org/oe-kbuild-all/202401310416.s8HLiLnC-lkp@xxxxxxxxx/
> > > Cc: Yoshinori Sato <ysato@xxxxxxxxxxxxxxxxxxxx>
> > > Cc: Rich Felker <dalias@xxxxxxxx>
> > > Cc: John Paul Adrian Glaubitz <glaubitz@xxxxxxxxxxxxxxxxxxx>
> > > Cc: Masahiro Yamada <masahiroy@xxxxxxxxxx>
> > > Cc: Nicolas Schier <n.schier@xxxxxx>
> > > Cc: linux-sh@xxxxxxxxxxxxxxx
> > > Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
> > > ---
> > >  arch/sh/boot/compressed/Makefile | 1 +
> > >  1 file changed, 1 insertion(+)
> > > 
> > > diff --git a/arch/sh/boot/compressed/Makefile b/arch/sh/boot/compressed/Makefile
> > > index b5e29f99c02c..6c6c791a1d06 100644
> > > --- a/arch/sh/boot/compressed/Makefile
> > > +++ b/arch/sh/boot/compressed/Makefile
> > > @@ -12,6 +12,7 @@ targets := vmlinux vmlinux.bin vmlinux.bin.gz vmlinux.bin.bz2 \
> > >             vmlinux.bin.lzma vmlinux.bin.xz vmlinux.bin.lzo $(OBJECTS)
> > >  
> > >  GCOV_PROFILE := n
> > > +UBSAN_SANITIZE := n
> > >  
> > >  #
> > >  # IMAGE_OFFSET is the load offset of the compression loader
> > 
> > Thanks for the patch. I'm looking into this now and will provide the review later.
> 
> I tried to reproduce the error using your tree and the branch devel/overflow/ubsan-only
> minus the above patch and using the provided config but I'm unable to reproduce the
> error above.
> 
> Am I missing anything?

When I use GCC 13.2 (I'm specifically on Ubuntu 23.10) and the randconfig
linked from the report:
https://download.01.org/0day-ci/archive/20240131/202401310416.s8HLiLnC-lkp@xxxxxxxxx/config
(which is notably enabling CONFIG_UBSAN=y and CONFIG_UBSAN_SHIFT=y) then I
see at the final link stage:

/usr/bin/sh4-linux-gnu-ld: arch/sh/boot/compressed/misc.o: in function `zlib_inflate_table':
misc.c:(.text+0x650): undefined reference to `__ubsan_handle_shift_out_of_bounds'
..

After the patch, it's solved.

-Kees

-- 
Kees Cook