[PATCH] riscv: Disable KSAN_SANITIZE for vDSO

[PATCH] riscv: Disable KSAN_SANITIZE for vDSO

[Tobias Klauser]

Dmitry Vyukov reports:
> I've localized one issue with riscv/KASAN:
> KASAN breaks VDSO and that's I think the root cause of weird faults I
> saw earlier. The following patch fixes it.
> Could somebody please upstream this fix? I don't know how to add/run
> tests for this.

Verified the fix on a kernel with KASAN enabled using vDSO selftests.

Link: https://lore.kernel.org/lkml/CACT4Y+ZNJBnkKHXUf=tm_yuowvZvHwN=0rmJ=7J+xFd+9r_6pQ@mail.gmail.com/
Cc: Dmitry Vyukov <dvyukov@google.com>
Tested-by: Tobias Klauser <tklauser@distanz.ch>
Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
---
 arch/riscv/kernel/vdso/Makefile | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/kernel/vdso/Makefile b/arch/riscv/kernel/vdso/Makefile
index 0cfd6da784f8..71a315e73cbe 100644
--- a/arch/riscv/kernel/vdso/Makefile
+++ b/arch/riscv/kernel/vdso/Makefile
@@ -32,9 +32,10 @@ CPPFLAGS_vdso.lds += -P -C -U$(ARCH)
 # Disable -pg to prevent insert call site
 CFLAGS_REMOVE_vgettimeofday.o = $(CC_FLAGS_FTRACE) -Os
 
-# Disable gcov profiling for VDSO code
+# Disable profiling and instrumentation for VDSO code
 GCOV_PROFILE := n
 KCOV_INSTRUMENT := n
+KASAN_SANITIZE := n
 
 # Force dependency
 $(obj)/vdso.o: $(obj)/vdso.so
-- 
2.30.0


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Re: [PATCH] riscv: Disable KSAN_SANITIZE for vDSO

[Dmitry Vyukov]

On Tue, Feb 16, 2021 at 6:33 PM Tobias Klauser <tklauser@distanz.ch> wrote:
>
> Dmitry Vyukov reports:
> > I've localized one issue with riscv/KASAN:
> > KASAN breaks VDSO and that's I think the root cause of weird faults I
> > saw earlier. The following patch fixes it.
> > Could somebody please upstream this fix? I don't know how to add/run
> > tests for this.
>
> Verified the fix on a kernel with KASAN enabled using vDSO selftests.
>
> Link: https://lore.kernel.org/lkml/CACT4Y+ZNJBnkKHXUf=tm_yuowvZvHwN=0rmJ=7J+xFd+9r_6pQ@mail.gmail.com/
> Cc: Dmitry Vyukov <dvyukov@google.com>
> Tested-by: Tobias Klauser <tklauser@distanz.ch>
> Signed-off-by: Tobias Klauser <tklauser@distanz.ch>

Thanks for the quick fix!

Tested-by: Dmitry Vyukov <dvyukov@google.com>

> ---
>  arch/riscv/kernel/vdso/Makefile | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/riscv/kernel/vdso/Makefile b/arch/riscv/kernel/vdso/Makefile
> index 0cfd6da784f8..71a315e73cbe 100644
> --- a/arch/riscv/kernel/vdso/Makefile
> +++ b/arch/riscv/kernel/vdso/Makefile
> @@ -32,9 +32,10 @@ CPPFLAGS_vdso.lds += -P -C -U$(ARCH)
>  # Disable -pg to prevent insert call site
>  CFLAGS_REMOVE_vgettimeofday.o = $(CC_FLAGS_FTRACE) -Os
>
> -# Disable gcov profiling for VDSO code
> +# Disable profiling and instrumentation for VDSO code
>  GCOV_PROFILE := n
>  KCOV_INSTRUMENT := n
> +KASAN_SANITIZE := n
>
>  # Force dependency
>  $(obj)/vdso.o: $(obj)/vdso.so
> --
> 2.30.0
>

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Re: [PATCH] riscv: Disable KSAN_SANITIZE for vDSO

[Palmer Dabbelt]

On Tue, 16 Feb 2021 09:33:05 PST (-0800), tklauser@distanz.ch wrote:
> Dmitry Vyukov reports:
>> I've localized one issue with riscv/KASAN:
>> KASAN breaks VDSO and that's I think the root cause of weird faults I
>> saw earlier. The following patch fixes it.
>> Could somebody please upstream this fix? I don't know how to add/run
>> tests for this.
>
> Verified the fix on a kernel with KASAN enabled using vDSO selftests.
>
> Link: https://lore.kernel.org/lkml/CACT4Y+ZNJBnkKHXUf=tm_yuowvZvHwN=0rmJ=7J+xFd+9r_6pQ@mail.gmail.com/
> Cc: Dmitry Vyukov <dvyukov@google.com>
> Tested-by: Tobias Klauser <tklauser@distanz.ch>
> Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
> ---
>  arch/riscv/kernel/vdso/Makefile | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/riscv/kernel/vdso/Makefile b/arch/riscv/kernel/vdso/Makefile
> index 0cfd6da784f8..71a315e73cbe 100644
> --- a/arch/riscv/kernel/vdso/Makefile
> +++ b/arch/riscv/kernel/vdso/Makefile
> @@ -32,9 +32,10 @@ CPPFLAGS_vdso.lds += -P -C -U$(ARCH)
>  # Disable -pg to prevent insert call site
>  CFLAGS_REMOVE_vgettimeofday.o = $(CC_FLAGS_FTRACE) -Os
>
> -# Disable gcov profiling for VDSO code
> +# Disable profiling and instrumentation for VDSO code
>  GCOV_PROFILE := n
>  KCOV_INSTRUMENT := n
> +KASAN_SANITIZE := n
>
>  # Force dependency
>  $(obj)/vdso.o: $(obj)/vdso.so

This seems reasonable.  Building the VDSO with asan results in a bunch of PLT
entries for the VDSO stubs.  I don't see a sane way to resolve those, and it
looks like this is what everyone else is doing.

That said, the commit text is a bit funny so I've written one of my own.  This
is on for-next, as it's still the merge window.  Let me know if the text
doesn't make sense.

Thanks!

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Re: [PATCH] riscv: Disable KSAN_SANITIZE for vDSO

[Tobias Klauser]

On 2021-02-19 at 08:15:34 +0100, Palmer Dabbelt <palmer@dabbelt.com> wrote:
> On Tue, 16 Feb 2021 09:33:05 PST (-0800), tklauser@distanz.ch wrote:
> > Dmitry Vyukov reports:
> > > I've localized one issue with riscv/KASAN:
> > > KASAN breaks VDSO and that's I think the root cause of weird faults I
> > > saw earlier. The following patch fixes it.
> > > Could somebody please upstream this fix? I don't know how to add/run
> > > tests for this.
> > 
> > Verified the fix on a kernel with KASAN enabled using vDSO selftests.
> > 
> > Link: https://lore.kernel.org/lkml/CACT4Y+ZNJBnkKHXUf=tm_yuowvZvHwN=0rmJ=7J+xFd+9r_6pQ@mail.gmail.com/
> > Cc: Dmitry Vyukov <dvyukov@google.com>
> > Tested-by: Tobias Klauser <tklauser@distanz.ch>
> > Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
> > ---
> >  arch/riscv/kernel/vdso/Makefile | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> > 
> > diff --git a/arch/riscv/kernel/vdso/Makefile b/arch/riscv/kernel/vdso/Makefile
> > index 0cfd6da784f8..71a315e73cbe 100644
> > --- a/arch/riscv/kernel/vdso/Makefile
> > +++ b/arch/riscv/kernel/vdso/Makefile
> > @@ -32,9 +32,10 @@ CPPFLAGS_vdso.lds += -P -C -U$(ARCH)
> >  # Disable -pg to prevent insert call site
> >  CFLAGS_REMOVE_vgettimeofday.o = $(CC_FLAGS_FTRACE) -Os
> > 
> > -# Disable gcov profiling for VDSO code
> > +# Disable profiling and instrumentation for VDSO code
> >  GCOV_PROFILE := n
> >  KCOV_INSTRUMENT := n
> > +KASAN_SANITIZE := n
> > 
> >  # Force dependency
> >  $(obj)/vdso.o: $(obj)/vdso.so
> 
> This seems reasonable.  Building the VDSO with asan results in a bunch of PLT
> entries for the VDSO stubs.  I don't see a sane way to resolve those, and it
> looks like this is what everyone else is doing.
> 
> That said, the commit text is a bit funny so I've written one of my own.  This
> is on for-next, as it's still the merge window.  Let me know if the text
> doesn't make sense.

Thanks for fixing up the commit message and adding the Fixes line. Makes
sense to me.

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