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Message-ID: <202006091149.6C78419@keescook>
Date: Tue, 9 Jun 2020 12:09:27 -0700
From: Kees Cook <keescook@...omium.org>
To: Will Deacon <will@...nel.org>
Cc: Alexander Popov <alex.popov@...ux.com>,
Emese Revfy <re.emese@...il.com>,
Miguel Ojeda <miguel.ojeda.sandonis@...il.com>,
Masahiro Yamada <masahiroy@...nel.org>,
Michal Marek <michal.lkml@...kovi.net>,
Andrew Morton <akpm@...ux-foundation.org>,
Masahiro Yamada <yamada.masahiro@...ionext.com>,
Thiago Jung Bauermann <bauerman@...ux.ibm.com>,
Luis Chamberlain <mcgrof@...nel.org>, Jessica Yu <jeyu@...nel.org>,
Sven Schnelle <svens@...ckframe.org>,
Iurii Zaikin <yzaikin@...gle.com>,
Catalin Marinas <catalin.marinas@....com>,
Vincenzo Frascino <vincenzo.frascino@....com>,
Thomas Gleixner <tglx@...utronix.de>,
Peter Collingbourne <pcc@...gle.com>,
Naohiro Aota <naohiro.aota@....com>,
Alexander Monakov <amonakov@...ras.ru>,
Mathias Krause <minipli@...glemail.com>,
PaX Team <pageexec@...email.hu>,
Brad Spengler <spender@...ecurity.net>,
Laura Abbott <labbott@...hat.com>,
Florian Weimer <fweimer@...hat.com>,
kernel-hardening@...ts.openwall.com, linux-kbuild@...r.kernel.org,
x86@...nel.org, linux-arm-kernel@...ts.infradead.org,
linux-kernel@...r.kernel.org, gcc@....gnu.org, notify@...nel.org
Subject: Re: [PATCH 5/5] gcc-plugins/stackleak: Don't instrument
vgettimeofday.c in arm64 VDSO
On Thu, Jun 04, 2020 at 02:58:06PM +0100, Will Deacon wrote:
> On Thu, Jun 04, 2020 at 04:49:57PM +0300, Alexander Popov wrote:
> > Don't try instrumenting functions in arch/arm64/kernel/vdso/vgettimeofday.c.
> > Otherwise that can cause issues if the cleanup pass of stackleak gcc plugin
> > is disabled.
> >
> > Signed-off-by: Alexander Popov <alex.popov@...ux.com>
> > ---
> > arch/arm64/kernel/vdso/Makefile | 3 ++-
> > 1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/arm64/kernel/vdso/Makefile b/arch/arm64/kernel/vdso/Makefile
> > index 3862cad2410c..9b84cafbd2da 100644
> > --- a/arch/arm64/kernel/vdso/Makefile
> > +++ b/arch/arm64/kernel/vdso/Makefile
> > @@ -32,7 +32,8 @@ UBSAN_SANITIZE := n
> > OBJECT_FILES_NON_STANDARD := y
> > KCOV_INSTRUMENT := n
> >
> > -CFLAGS_vgettimeofday.o = -O2 -mcmodel=tiny -fasynchronous-unwind-tables
> > +CFLAGS_vgettimeofday.o = -O2 -mcmodel=tiny -fasynchronous-unwind-tables \
> > + $(DISABLE_STACKLEAK_PLUGIN)
>
> I can pick this one up via arm64, thanks. Are there any other plugins we
> should be wary of? It looks like x86 filters out $(GCC_PLUGINS_CFLAGS)
> when building the vDSO.
I didn't realize/remember that arm64 retained the kernel build flags for
vDSO builds. (I'm used to x86 throwing all its flags away for its vDSO.)
How does 32-bit ARM do its vDSO?
My quick run-through on plugins:
arm_ssp_per_task_plugin.c
32-bit ARM only (but likely needs disabling for 32-bit ARM vDSO?)
cyc_complexity_plugin.c
compile-time reporting only
latent_entropy_plugin.c
this shouldn't get triggered for the vDSO (no __latent_entropy
nor __init attributes in vDSO), but perhaps explicitly disabling
it would be a sensible thing to do, just for robustness?
randomize_layout_plugin.c
this shouldn't get triggered (again, lacking attributes), but
should likely be disabled too.
sancov_plugin.c
This should be tracking the KCOV directly (see
scripts/Makefile.kcov), which is already disabled here.
structleak_plugin.c
This should be fine in the vDSO, but there's not security
boundary here, so it wouldn't be important to KEEP it enabled.
--
Kees Cook
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