[PATCH] sparc: vdso: Disable UBSAN instrumentation

[PATCH] sparc: vdso: Disable UBSAN instrumentation

[Kees Cook]

The UBSAN instrumentation cannot work in the vDSO since it is executing
in userspace, so disable it in the Makefile. Fixes the build failures
such as:

arch/sparc/vdso/vclock_gettime.c:217: undefined reference to `__ubsan_handle_shift_out_of_bounds'

Signed-off-by: Kees Cook <keescook@chromium.org>
---
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Andreas Larsson <andreas@gaisler.com>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Helge Deller <deller@gmx.de>
Cc: Guo Ren <guoren@kernel.org>
Cc: sparclinux@vger.kernel.org
---
 arch/sparc/vdso/Makefile | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/sparc/vdso/Makefile b/arch/sparc/vdso/Makefile
index 7f5eedf1f5e0..e8aef2c8ae99 100644
--- a/arch/sparc/vdso/Makefile
+++ b/arch/sparc/vdso/Makefile
@@ -2,6 +2,7 @@
 #
 # Building vDSO images for sparc.
 #
+UBSAN_SANITIZE := n
 
 # files to link into the vdso
 vobjs-y := vdso-note.o vclock_gettime.o
-- 
2.34.1

Re: [PATCH] sparc: vdso: Disable UBSAN instrumentation

[Sam Ravnborg]

Hi Kees,

On Fri, Feb 23, 2024 at 08:59:45AM -0800, Kees Cook wrote:
> The UBSAN instrumentation cannot work in the vDSO since it is executing
> in userspace, so disable it in the Makefile. Fixes the build failures
> such as:
> 
> arch/sparc/vdso/vclock_gettime.c:217: undefined reference to `__ubsan_handle_shift_out_of_bounds'
> 
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
> Cc: "David S. Miller" <davem@davemloft.net>
> Cc: Andreas Larsson <andreas@gaisler.com>
> Cc: Masahiro Yamada <masahiroy@kernel.org>
> Cc: Sam Ravnborg <sam@ravnborg.org>
> Cc: Helge Deller <deller@gmx.de>
> Cc: Guo Ren <guoren@kernel.org>
> Cc: sparclinux@vger.kernel.org
> ---
>  arch/sparc/vdso/Makefile | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/arch/sparc/vdso/Makefile b/arch/sparc/vdso/Makefile
> index 7f5eedf1f5e0..e8aef2c8ae99 100644
> --- a/arch/sparc/vdso/Makefile
> +++ b/arch/sparc/vdso/Makefile
> @@ -2,6 +2,7 @@
>  #
>  # Building vDSO images for sparc.
>  #
> +UBSAN_SANITIZE := n

When I read:

config UBSAN_SANITIZE_ALL
        bool "Enable instrumentation for the entire kernel"
        depends on ARCH_HAS_UBSAN_SANITIZE_ALL
        default y
        help
          This option activates instrumentation for the entire kernel.
          If you don't enable this option, you have to explicitly specify
          UBSAN_SANITIZE := y for the files/directories you want to check for UB.
          Enabling this option will get kernel image size increased
          significantly.


I am left with the understanding that only arch's that
selects ARCH_HAS_UBSAN_SANITIZE_ALL would need to turn off
UBSAN_SANITIZE.

Are this fix papering over some other bug where we enable
UBSAN_SANITIZE_ALL for arch's that should not have it,
or something else that enable it?

	Sam

Re: [PATCH] sparc: vdso: Disable UBSAN instrumentation

[Kees Cook]

On Fri, Feb 23, 2024 at 07:26:46PM +0100, Sam Ravnborg wrote:
> Hi Kees,
> 
> On Fri, Feb 23, 2024 at 08:59:45AM -0800, Kees Cook wrote:
> > The UBSAN instrumentation cannot work in the vDSO since it is executing
> > in userspace, so disable it in the Makefile. Fixes the build failures
> > such as:
> > 
> > arch/sparc/vdso/vclock_gettime.c:217: undefined reference to `__ubsan_handle_shift_out_of_bounds'
> > 
> > Signed-off-by: Kees Cook <keescook@chromium.org>
> > ---
> > Cc: "David S. Miller" <davem@davemloft.net>
> > Cc: Andreas Larsson <andreas@gaisler.com>
> > Cc: Masahiro Yamada <masahiroy@kernel.org>
> > Cc: Sam Ravnborg <sam@ravnborg.org>
> > Cc: Helge Deller <deller@gmx.de>
> > Cc: Guo Ren <guoren@kernel.org>
> > Cc: sparclinux@vger.kernel.org
> > ---
> >  arch/sparc/vdso/Makefile | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/arch/sparc/vdso/Makefile b/arch/sparc/vdso/Makefile
> > index 7f5eedf1f5e0..e8aef2c8ae99 100644
> > --- a/arch/sparc/vdso/Makefile
> > +++ b/arch/sparc/vdso/Makefile
> > @@ -2,6 +2,7 @@
> >  #
> >  # Building vDSO images for sparc.
> >  #
> > +UBSAN_SANITIZE := n
> 
> When I read:
> 
> config UBSAN_SANITIZE_ALL
>         bool "Enable instrumentation for the entire kernel"
>         depends on ARCH_HAS_UBSAN_SANITIZE_ALL
>         default y
>         help
>           This option activates instrumentation for the entire kernel.
>           If you don't enable this option, you have to explicitly specify
>           UBSAN_SANITIZE := y for the files/directories you want to check for UB.
>           Enabling this option will get kernel image size increased
>           significantly.
> 
> 
> I am left with the understanding that only arch's that
> selects ARCH_HAS_UBSAN_SANITIZE_ALL would need to turn off
> UBSAN_SANITIZE.

Ah, right. So, I removed[1] UBSAN_SANITIZE_ALL in -next (it was the only
sanitizer using this logic) and this appears to be one of the impacts. :)
I sent similar fixes for sh[2] and LoongArch[3].

> Are this fix papering over some other bug where we enable
> UBSAN_SANITIZE_ALL for arch's that should not have it,
> or something else that enable it?

It's possible we should implement HAVE_ARCH_UBSAN, but in my testing
everything built fine with it, so I didn't opt to do that (it looked
like just additional configs for no real benefit). What do you think?

-Kees

[1] https://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git/commit/?h=for-next/kspp&id=918327e9b7ffb45321cbb4b9b86b58ec555fe6b3
[2] https://lore.kernel.org/lkml/20240130232717.work.088-kees@kernel.org/
[3] https://lore.kernel.org/lkml/20240130233140.work.887-kees@kernel.org/

-- 
Kees Cook

Re: [PATCH] sparc: vdso: Disable UBSAN instrumentation

[Sam Ravnborg]

Hi Kees,

On Fri, Feb 23, 2024 at 03:32:37PM -0800, Kees Cook wrote:
> On Fri, Feb 23, 2024 at 07:26:46PM +0100, Sam Ravnborg wrote:
> > Hi Kees,
> > 
> > On Fri, Feb 23, 2024 at 08:59:45AM -0800, Kees Cook wrote:
> > > The UBSAN instrumentation cannot work in the vDSO since it is executing
> > > in userspace, so disable it in the Makefile. Fixes the build failures
> > > such as:
> > > 
> > > arch/sparc/vdso/vclock_gettime.c:217: undefined reference to `__ubsan_handle_shift_out_of_bounds'
> > > 
> > > Signed-off-by: Kees Cook <keescook@chromium.org>
> > > ---
> > > Cc: "David S. Miller" <davem@davemloft.net>
> > > Cc: Andreas Larsson <andreas@gaisler.com>
> > > Cc: Masahiro Yamada <masahiroy@kernel.org>
> > > Cc: Sam Ravnborg <sam@ravnborg.org>
> > > Cc: Helge Deller <deller@gmx.de>
> > > Cc: Guo Ren <guoren@kernel.org>
> > > Cc: sparclinux@vger.kernel.org
> > > ---
> > >  arch/sparc/vdso/Makefile | 1 +
> > >  1 file changed, 1 insertion(+)
> > > 
> > > diff --git a/arch/sparc/vdso/Makefile b/arch/sparc/vdso/Makefile
> > > index 7f5eedf1f5e0..e8aef2c8ae99 100644
> > > --- a/arch/sparc/vdso/Makefile
> > > +++ b/arch/sparc/vdso/Makefile
> > > @@ -2,6 +2,7 @@
> > >  #
> > >  # Building vDSO images for sparc.
> > >  #
> > > +UBSAN_SANITIZE := n
> > 
> > When I read:
> > 
> > config UBSAN_SANITIZE_ALL
> >         bool "Enable instrumentation for the entire kernel"
> >         depends on ARCH_HAS_UBSAN_SANITIZE_ALL
> >         default y
> >         help
> >           This option activates instrumentation for the entire kernel.
> >           If you don't enable this option, you have to explicitly specify
> >           UBSAN_SANITIZE := y for the files/directories you want to check for UB.
> >           Enabling this option will get kernel image size increased
> >           significantly.
> > 
> > 
> > I am left with the understanding that only arch's that
> > selects ARCH_HAS_UBSAN_SANITIZE_ALL would need to turn off
> > UBSAN_SANITIZE.
> 
> Ah, right. So, I removed[1] UBSAN_SANITIZE_ALL in -next (it was the only
> sanitizer using this logic) and this appears to be one of the impacts. :)
> I sent similar fixes for sh[2] and LoongArch[3].
> 
> > Are this fix papering over some other bug where we enable
> > UBSAN_SANITIZE_ALL for arch's that should not have it,
> > or something else that enable it?
> 
> It's possible we should implement HAVE_ARCH_UBSAN, but in my testing
> everything built fine with it, so I didn't opt to do that (it looked
> like just additional configs for no real benefit). What do you think?

Coffee has not yet kicked in, but...


> [1] https://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git/commit/?h=for-next/kspp&id=918327e9b7ffb45321cbb4b9b86b58ec555fe6b3

OK, I did not have this patch in my tree so it explain the need for the
patch in this mail. Looking at the linked patch the ARCH_HAS_UBSAN symbol
is selected by some architecture but I see no use of it. Maybe that is a
later patch and then all is good.


In general I am not fan of naked config symbols (no help / comment) like this:
config ARCH_HAS_UBSAN
 	bool

The reader is left only with the symbol name trying to understand the
purpose of a symbol that is selected by some architectures.
But that is a different matter for another day.

As you now put the patch in this mail in context it makes sense and it has my:
Acked-by: Sam Ravnborg <sam@ravnborg.org>

	Sam

Re: [PATCH] sparc: vdso: Disable UBSAN instrumentation

[Andy Shevchenko]

On Fri, Feb 23, 2024 at 08:59:45AM -0800, Kees Cook wrote:
> The UBSAN instrumentation cannot work in the vDSO since it is executing
> in userspace, so disable it in the Makefile. Fixes the build failures
> such as:
> 
> arch/sparc/vdso/vclock_gettime.c:217: undefined reference to `__ubsan_handle_shift_out_of_bounds'
> 
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
> Cc: "David S. Miller" <davem@davemloft.net>
> Cc: Andreas Larsson <andreas@gaisler.com>
> Cc: Masahiro Yamada <masahiroy@kernel.org>
> Cc: Sam Ravnborg <sam@ravnborg.org>
> Cc: Helge Deller <deller@gmx.de>
> Cc: Guo Ren <guoren@kernel.org>
> Cc: sparclinux@vger.kernel.org

I dunno how you applied patches, but these Cc seems to appear in a few commits
in your hardening branch.

I formatted patch from 9fd54b08040669, checked out the new branch just before
this commit and run `git am 0001-...`. I don't see them.

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH] sparc: vdso: Disable UBSAN instrumentation

[Kees Cook]

On Thu, Feb 29, 2024 at 10:00:38PM +0200, Andy Shevchenko wrote:
> On Fri, Feb 23, 2024 at 08:59:45AM -0800, Kees Cook wrote:
> > The UBSAN instrumentation cannot work in the vDSO since it is executing
> > in userspace, so disable it in the Makefile. Fixes the build failures
> > such as:
> > 
> > arch/sparc/vdso/vclock_gettime.c:217: undefined reference to `__ubsan_handle_shift_out_of_bounds'
> > 
> > Signed-off-by: Kees Cook <keescook@chromium.org>
> > ---
> > Cc: "David S. Miller" <davem@davemloft.net>
> > Cc: Andreas Larsson <andreas@gaisler.com>
> > Cc: Masahiro Yamada <masahiroy@kernel.org>
> > Cc: Sam Ravnborg <sam@ravnborg.org>
> > Cc: Helge Deller <deller@gmx.de>
> > Cc: Guo Ren <guoren@kernel.org>
> > Cc: sparclinux@vger.kernel.org
> 
> I dunno how you applied patches, but these Cc seems to appear in a few commits
> in your hardening branch.
> 
> I formatted patch from 9fd54b08040669, checked out the new branch just before
> this commit and run `git am 0001-...`. I don't see them.

Ah, hm, yes, I'll need to split up my trees a bit to get the right
results. Thanks for pointing that out!

-- 
Kees Cook