From: George Popescu <[email protected]>
When the kernel is compiled with Clang, -fsanitize=bounds expands to
-fsanitize=array-bounds and -fsanitize=local-bounds.
Enabling -fsanitize=local-bounds with Clang has the unfortunate
side-effect of inserting traps; this goes back to its original intent,
which was as a hardening and not a debugging feature [1]. The same feature
made its way into -fsanitize=bounds, but the traps remained. For that
reason, -fsanitize=bounds was split into 'array-bounds' and
'local-bounds' [2].
Since 'local-bounds' doesn't behave like a normal sanitizer, enable
it with Clang only if trapping behaviour was requested by
CONFIG_UBSAN_TRAP=y.
Add the UBSAN_BOUNDS_LOCAL config to Kconfig.ubsan to enable the
'local-bounds' option by default when UBSAN_TRAP is enabled.
[1] http://lists.llvm.org/pipermail/llvm-dev/2012-May/049972.html
[2] http://lists.llvm.org/pipermail/cfe-commits/Week-of-Mon-20131021/091536.html
Suggested-by: Marco Elver <[email protected]>
Reviewed-by: David Brazdil <[email protected]>
Signed-off-by: George Popescu <[email protected]>
---
lib/Kconfig.ubsan | 14 ++++++++++++++
scripts/Makefile.ubsan | 10 +++++++++-
2 files changed, 23 insertions(+), 1 deletion(-)
diff --git a/lib/Kconfig.ubsan b/lib/Kconfig.ubsan
index 774315de555a..553bd22e83ee 100644
--- a/lib/Kconfig.ubsan
+++ b/lib/Kconfig.ubsan
@@ -47,6 +47,20 @@ config UBSAN_BOUNDS
to the {str,mem}*cpy() family of functions (that is addressed
by CONFIG_FORTIFY_SOURCE).
+config UBSAN_BOUNDS_LOCAL
+ bool "Perform array local bounds checking"
+ depends on UBSAN_TRAP
+ depends on CC_IS_CLANG
+ depends on !UBSAN_KCOV_BROKEN
+ help
+ This option enables -fsanitize=local-bounds which traps when an
+ exception/error is detected. Therefore, it should be enabled only
+ if trapping is expected.
+ Enabling this option detects errors due to accesses through a
+ pointer that is derived from an object of a statically-known size,
+ where an added offset (which may not be known statically) is
+ out-of-bounds.
+
config UBSAN_MISC
bool "Enable all other Undefined Behavior sanity checks"
default UBSAN
diff --git a/scripts/Makefile.ubsan b/scripts/Makefile.ubsan
index 27348029b2b8..4e3fff0745e8 100644
--- a/scripts/Makefile.ubsan
+++ b/scripts/Makefile.ubsan
@@ -4,7 +4,15 @@ ifdef CONFIG_UBSAN_ALIGNMENT
endif
ifdef CONFIG_UBSAN_BOUNDS
- CFLAGS_UBSAN += $(call cc-option, -fsanitize=bounds)
+ ifdef CONFIG_CC_IS_CLANG
+ CFLAGS_UBSAN += -fsanitize=array-bounds
+ else
+ CFLAGS_UBSAN += $(call cc-option, -fsanitize=bounds)
+ endif
+endif
+
+ifdef CONFIG_UBSAN_LOCAL_BOUNDS
+ CFLAGS_UBSAN += -fsanitize=local-bounds
endif
ifdef CONFIG_UBSAN_MISC
--
2.28.0.681.g6f77f65b4e-goog
On Fri, 18 Sep 2020 at 15:36, George-Aurelian Popescu
<[email protected]> wrote:
>
> From: George Popescu <[email protected]>
>
[...]
> Suggested-by: Marco Elver <[email protected]>
> Reviewed-by: David Brazdil <[email protected]>
> Signed-off-by: George Popescu <[email protected]>
There's a mismatch between From/Author and Signed-off-by email address.
> ---
> lib/Kconfig.ubsan | 14 ++++++++++++++
> scripts/Makefile.ubsan | 10 +++++++++-
> 2 files changed, 23 insertions(+), 1 deletion(-)
>
> diff --git a/lib/Kconfig.ubsan b/lib/Kconfig.ubsan
> index 774315de555a..553bd22e83ee 100644
> --- a/lib/Kconfig.ubsan
> +++ b/lib/Kconfig.ubsan
> @@ -47,6 +47,20 @@ config UBSAN_BOUNDS
> to the {str,mem}*cpy() family of functions (that is addressed
> by CONFIG_FORTIFY_SOURCE).
>
> +config UBSAN_BOUNDS_LOCAL
> + bool "Perform array local bounds checking"
> + depends on UBSAN_TRAP
> + depends on CC_IS_CLANG
> + depends on !UBSAN_KCOV_BROKEN
> + help
> + This option enables -fsanitize=local-bounds which traps when an
> + exception/error is detected. Therefore, it should be enabled only
> + if trapping is expected.
> + Enabling this option detects errors due to accesses through a
> + pointer that is derived from an object of a statically-known size,
> + where an added offset (which may not be known statically) is
> + out-of-bounds.
> +
> config UBSAN_MISC
> bool "Enable all other Undefined Behavior sanity checks"
> default UBSAN
> diff --git a/scripts/Makefile.ubsan b/scripts/Makefile.ubsan
> index 27348029b2b8..4e3fff0745e8 100644
> --- a/scripts/Makefile.ubsan
> +++ b/scripts/Makefile.ubsan
> @@ -4,7 +4,15 @@ ifdef CONFIG_UBSAN_ALIGNMENT
> endif
>
> ifdef CONFIG_UBSAN_BOUNDS
> - CFLAGS_UBSAN += $(call cc-option, -fsanitize=bounds)
> + ifdef CONFIG_CC_IS_CLANG
> + CFLAGS_UBSAN += -fsanitize=array-bounds
> + else
> + CFLAGS_UBSAN += $(call cc-option, -fsanitize=bounds)
> + endif
> +endif
> +
> +ifdef CONFIG_UBSAN_LOCAL_BOUNDS
Unsure what happened here, but your Kconfig option is named
UBSAN_BOUNDS_LOCAL, yet this uses CONFIG_UBSAN_LOCAL_BOUNDS, so this
patch unfortunately doesn't work yet as you intended.
> + CFLAGS_UBSAN += -fsanitize=local-bounds
> endif
Thanks,
-- Marco