Both KCOV and UBSAN use compiler instrumentation. If UBSAN detects a bug
in KCOV, it may cause infinite recursion via printk and other common
functions. We already don't instrument KCOV with KASAN/KCSAN for this
reason, don't instrument it with UBSAN as well.
As a side effect this also resolves the following gcc warning:
conflicting types for built-in function '__sanitizer_cov_trace_switch';
expected 'void(long unsigned int, void *)' [-Wbuiltin-declaration-mismatch]
It's only reported when kcov.c is compiled with any of the sanitizers
enabled. Size of the arguments is correct, it's just that gcc uses 'long'
on 64-bit arches and 'long long' on 32-bit arches, while kernel type is
always 'long long'.
Reported-by: Stephen Rothwell <[email protected]>
Suggested-by: Marco Elver <[email protected]>
Signed-off-by: Dmitry Vyukov <[email protected]>
---
kernel/Makefile | 3 +++
1 file changed, 3 insertions(+)
diff --git a/kernel/Makefile b/kernel/Makefile
index aac15aeb9d69..efa42857532b 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -34,8 +34,11 @@ KCOV_INSTRUMENT_extable.o := n
KCOV_INSTRUMENT_stacktrace.o := n
# Don't self-instrument.
KCOV_INSTRUMENT_kcov.o := n
+# If sanitizers detect any issues in kcov, it may lead to recursion
+# via printk, etc.
KASAN_SANITIZE_kcov.o := n
KCSAN_SANITIZE_kcov.o := n
+UBSAN_SANITIZE_kcov.o := n
CFLAGS_kcov.o := $(call cc-option, -fno-conserve-stack) -fno-stack-protector
obj-y += sched/
--
2.29.2.576.ga3fc446d84-goog
On Wed, 9 Dec 2020 at 11:01, Dmitry Vyukov <[email protected]> wrote:
>
> Both KCOV and UBSAN use compiler instrumentation. If UBSAN detects a bug
> in KCOV, it may cause infinite recursion via printk and other common
> functions. We already don't instrument KCOV with KASAN/KCSAN for this
> reason, don't instrument it with UBSAN as well.
>
> As a side effect this also resolves the following gcc warning:
>
> conflicting types for built-in function '__sanitizer_cov_trace_switch';
> expected 'void(long unsigned int, void *)' [-Wbuiltin-declaration-mismatch]
>
> It's only reported when kcov.c is compiled with any of the sanitizers
> enabled. Size of the arguments is correct, it's just that gcc uses 'long'
> on 64-bit arches and 'long long' on 32-bit arches, while kernel type is
> always 'long long'.
>
> Reported-by: Stephen Rothwell <[email protected]>
> Suggested-by: Marco Elver <[email protected]>
> Signed-off-by: Dmitry Vyukov <[email protected]>
Acked-by: Marco Elver <[email protected]>
> ---
> kernel/Makefile | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/kernel/Makefile b/kernel/Makefile
> index aac15aeb9d69..efa42857532b 100644
> --- a/kernel/Makefile
> +++ b/kernel/Makefile
> @@ -34,8 +34,11 @@ KCOV_INSTRUMENT_extable.o := n
> KCOV_INSTRUMENT_stacktrace.o := n
> # Don't self-instrument.
> KCOV_INSTRUMENT_kcov.o := n
> +# If sanitizers detect any issues in kcov, it may lead to recursion
> +# via printk, etc.
> KASAN_SANITIZE_kcov.o := n
> KCSAN_SANITIZE_kcov.o := n
> +UBSAN_SANITIZE_kcov.o := n
> CFLAGS_kcov.o := $(call cc-option, -fno-conserve-stack) -fno-stack-protector
>
> obj-y += sched/
> --
> 2.29.2.576.ga3fc446d84-goog
>
On Wed, Dec 9, 2020 at 11:01 AM Dmitry Vyukov <[email protected]> wrote:
>
> Both KCOV and UBSAN use compiler instrumentation. If UBSAN detects a bug
> in KCOV, it may cause infinite recursion via printk and other common
> functions. We already don't instrument KCOV with KASAN/KCSAN for this
> reason, don't instrument it with UBSAN as well.
>
> As a side effect this also resolves the following gcc warning:
>
> conflicting types for built-in function '__sanitizer_cov_trace_switch';
> expected 'void(long unsigned int, void *)' [-Wbuiltin-declaration-mismatch]
>
> It's only reported when kcov.c is compiled with any of the sanitizers
> enabled. Size of the arguments is correct, it's just that gcc uses 'long'
> on 64-bit arches and 'long long' on 32-bit arches, while kernel type is
> always 'long long'.
>
> Reported-by: Stephen Rothwell <[email protected]>
> Suggested-by: Marco Elver <[email protected]>
> Signed-off-by: Dmitry Vyukov <[email protected]>
> ---
> kernel/Makefile | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/kernel/Makefile b/kernel/Makefile
> index aac15aeb9d69..efa42857532b 100644
> --- a/kernel/Makefile
> +++ b/kernel/Makefile
> @@ -34,8 +34,11 @@ KCOV_INSTRUMENT_extable.o := n
> KCOV_INSTRUMENT_stacktrace.o := n
> # Don't self-instrument.
> KCOV_INSTRUMENT_kcov.o := n
> +# If sanitizers detect any issues in kcov, it may lead to recursion
> +# via printk, etc.
> KASAN_SANITIZE_kcov.o := n
> KCSAN_SANITIZE_kcov.o := n
> +UBSAN_SANITIZE_kcov.o := n
> CFLAGS_kcov.o := $(call cc-option, -fno-conserve-stack) -fno-stack-protector
>
> obj-y += sched/
> --
> 2.29.2.576.ga3fc446d84-goog
>
Reviewed-by: Andrey Konovalov <[email protected]>
On Wed, Dec 09, 2020 at 11:01:52AM +0100, Dmitry Vyukov wrote:
> Both KCOV and UBSAN use compiler instrumentation. If UBSAN detects a bug
> in KCOV, it may cause infinite recursion via printk and other common
> functions. We already don't instrument KCOV with KASAN/KCSAN for this
> reason, don't instrument it with UBSAN as well.
>
> As a side effect this also resolves the following gcc warning:
>
> conflicting types for built-in function '__sanitizer_cov_trace_switch';
> expected 'void(long unsigned int, void *)' [-Wbuiltin-declaration-mismatch]
>
> It's only reported when kcov.c is compiled with any of the sanitizers
> enabled. Size of the arguments is correct, it's just that gcc uses 'long'
> on 64-bit arches and 'long long' on 32-bit arches, while kernel type is
> always 'long long'.
>
> Reported-by: Stephen Rothwell <[email protected]>
> Suggested-by: Marco Elver <[email protected]>
> Signed-off-by: Dmitry Vyukov <[email protected]>
Reviewed-by: Kees Cook <[email protected]>
Thanks for chasing this down!
Andrew, can you add this to the stack of ubsan patches you're carrying,
please?
--
Kees Cook
Hi all,
On Wed, 9 Dec 2020 10:54:39 -0800 Kees Cook <[email protected]> wrote:
>
> On Wed, Dec 09, 2020 at 11:01:52AM +0100, Dmitry Vyukov wrote:
> > Both KCOV and UBSAN use compiler instrumentation. If UBSAN detects a bug
> > in KCOV, it may cause infinite recursion via printk and other common
> > functions. We already don't instrument KCOV with KASAN/KCSAN for this
> > reason, don't instrument it with UBSAN as well.
> >
> > As a side effect this also resolves the following gcc warning:
> >
> > conflicting types for built-in function '__sanitizer_cov_trace_switch';
> > expected 'void(long unsigned int, void *)' [-Wbuiltin-declaration-mismatch]
> >
> > It's only reported when kcov.c is compiled with any of the sanitizers
> > enabled. Size of the arguments is correct, it's just that gcc uses 'long'
> > on 64-bit arches and 'long long' on 32-bit arches, while kernel type is
> > always 'long long'.
> >
> > Reported-by: Stephen Rothwell <[email protected]>
> > Suggested-by: Marco Elver <[email protected]>
> > Signed-off-by: Dmitry Vyukov <[email protected]>
>
> Reviewed-by: Kees Cook <[email protected]>
>
> Thanks for chasing this down!
>
> Andrew, can you add this to the stack of ubsan patches you're carrying,
> please?
Added to linux-next today.
--
Cheers,
Stephen Rothwell